Introduction Integrated Water Meter Management - MILE

EDITION 1TT 490/11

INTRODUCTION TOINTEGRATEDWATER METER MANAGEMENTEDITION 1JE VAN ZYLWAT E RR E S E A R C HC O M M I S S I O NTT 490/11

Obtainable from:Water Research CommissionPrivate Bag X03Gezina, 0031orders@wrc.org.zaThe publication of this report emanates from a project entitled Integrated Water MeterManagement (WRC Project No. K5/1814)DisclaimerThis report has been reviewed by the Water Research Commission (WRC) andapproved for publication. Approval does not signify that the contents necessarily reflectthe views and policies of the WRC, nor does mention of trade names or commercialproducts constitute endorsement or recommendation for use.ISBN 978-1-4312-0117-4Printed in the Republic of South AfricaOctober 2011Designer: Jacob KrynauwCover design and illustration: Jacob Krynauwii

ForewordA reliable supply of clean and healthy water isundoubtedly the most important service thatpeople need. South Africa has made great stridesin addressing the inequalities of the past in theprovision of water, but unfortunately the focuson providing more people with water has causedmany distribution systems to be neglected,resulting in increased levels of leakage and nonrevenuewater, poor billing practices and a loss ofincome to municipalities. It is vital to maximizethe volume of water metered in the utility, at theminimum possible cost. To achieve this goal, theproper selection, management and maintenanceof meters are critical.JN BhagwanDirector: Water Use and WasteManagementWater Research CommissionCurrently there is a lack in the propermanagement of water meters and meter data,resulting in increased levels of water losses andreduced income for municipalities. In addition,initiatives of water demand management andconservation are hampered by a lack of goodinformation.This book covers all aspects of water metersand water metering in municipalities. It coversthe theoretical principles of meters, legal andmetrological requirements, meter types, bestpractice guidelines as well as practical aspects ofwater meter management (amongst others).It is anticipated that this book will serve as atraining aid and a valuable tool for water utilitymanagers, engineering technical staff, operationsand maintenance and meter reading personneland researchers.It thus gives me great pleasure to support andfully endorse this excellent new book on watermetering. My wish is that that it will make areal difference to water management and servicedelivery both in South Africa and the rest of theworld.iii

AcknowledgmentsThis guide book emanated from a project initiated and funded by theWater Research Commission as Project K5/1814: Integrated WaterMeter Management.Particular credit and thanks are due to Mr J Bhagwan of the WaterResearch Commission, who initiated the project and chaired theReference Group. I would also like to acknowledge the other membersof the Reference Group and thank them for their time and guidance:Mr K Bailey (Elster Kent), Mr B Bold (Sensus), Mr L Hlatshwayo(Department of Water Affairs), Ms S Mabaso (Department ofWater Affairs), Ms M Machaba (Department of Water Affairs), DrR McKenzie (WRP), Ms S Moshidi (Department of Water Affairs),Mr V Naidoo (Arcus Gibb), Mr S Scruton (eThekwini Water andSanitation), Mr C Tsatsi (Department of Water Affairs), Mr D vanEeden (Sensus) and Mr T Westman (City of Tshwane).A number of individuals contributed sections of the book and/orprovided detailed feedback that were essential to make the book whatit is. I would like to particularly acknowledge the contributions of MrM Capper (Elster Kent), Mr F Couvelis (University of Cape Town),Mr R Davis (Ikapa), Mr I de Beer (Reonet), Ms K Fair (GLS), Mr MKubwalo (Itron) and Mr M Rabé (Re-Solve). Many others providedadvice or encouragement, including Mr B Beard (SABS), Mr EJohnson (GHD), Mr. R Kalil (Aqua-Loc), Mr A Leonie and Mr TLeonie.I would like to acknowledge and thank Mr J Wolmarans (Wordsource)for proof reading and most of the photographs in the book, and Mr JKrynauw (K2) for the book layout and figures.I would like to thank the University of Johannesburg for administrativesupport, the University of Cape Town for allowing me time to work onthe project, and the many individuals and organisations not mentionedwho contributed in various ways to this book.Finally, I would like to thank my wife Hanlie and children Jean andAnkia for their unwavering love and encouragement throughout thewriting of the book.iv

What others have said about Introduction to IntegratedWater Meter Management:“This book is a great resource for municipalities and will help them makeinformed decision in metering challenges.” “I am very impressed with theway it is written, it talks to the practical issues and challenges.”Zolile Basholo, Manager of Water Demand Management & Strategy,City of Cape Town“This informative book is easy to read and places the basics of water metermanagement at the finger tips of both professionals and novices alike. Ihighly recommend that this book is read by all water practitioners as itsuccinctly covers all aspects of meter management from selection, to installation,to operation and maintenance and finally to replacement.”Simon Scruton, Manager, eThekwini Water and Sanitation“The various technical and managerial concepts in the book are dealt within a practical and concise way and the numerous photographs, illustrationsand diagrams are well selected. This book should be required reading for everywater meter practitioner, regardless of their level of knowledge or skill.”Trevor Westman, Deputy Director: Water Loss and MeterManagement, City of Tshwane“As a billing agent, the book provides a lot of useful information on meters& billing. Excellent for billing & projects.”Kogie Govender, Sembcorp Siza Water“Very concise and informative. A must have for every engineer workingwith utilities!”Arno Marais, Chief Commissioning Engineer, Sasol“Though targeted for people in the municipalities who deal with metersevery day, the book is very handy even for consulting engineers, especially inthis day & age where water management is a global concern.”Tellmore Masocha, African Innovative Solutions & Projects“Brilliant and useful guide for basic water meter management and understandingof different water meter types for selection purposes.”Johan Pretorius, Aurecon“This is a well structured and informative textbook and tool. It has beenlong overdue in the water industry.”Nathaniel Padayachee, Jeffares and Greenv

“this book is very useful for all parties involved in water distributionoptimization and gives quick and simple answers to difficult questions.”Ignacio Pena, Joat Group“Training is the key to improving skills in order to manage water, our mostprecious resource. Water meters are the ‘cash tills’ of the reticulation. Thisexcellent book provides an outstanding reference for training.”Keith Bailey, General Manager: Sales & Marketing, Elster Kent“ This book is a must read for anyone in the water metering business,whether experienced or novice. The book is informative and the explanationsare excellent.”John Alexander, Sales and Marketing Manager, Krohne“This book presents the essential basic concepts of water meter selection andmanagement. It provides a balanced view of the different technologies ofwater meters currently available on the market and most importantly, theadvantages and disadvantages of these different technologies. Written inan accessible style and format, this book is a must for water practitioners.”Max Kubwalo, Itronvi

Table of ContentsTable of ConTenTsForewordAcknowledgmentsWhat others have said about Introduction to IntegratedWater Meter ManagementTable of ContentsiiiivvviiChapter 1: Introduction 11.1 Why this Book? 11.2 Why Water Metering? 21.2.1 Equity 21.2.2 Water Efficiency and Losses 21.2.3 Economic Benefits 31.2.4 System Management 31.3 About this book 41.3.1 Who Should Read this Book? 4Table of ConTenTs1.3.2 How are the Chapters Organised? 41.3.3 A Few Tips for Getting More out of this Book 4Chapter 2: Water Meter Basics 72.1 Introduction 72.2 Water Meters and Their Components 82.2.1 Sensor 92.2.2 Transducer 102.2.3 Counter 102.2.4 Indicator 10vii

Table of Contents2.2.5 Wet and Dry Dial Meters 112.2.6 Additional Meter Components 122.3 Legislation and Standards 132.3.1 Legislation 132.3.2 Standards 132.4 Metrology 142.4.1 Definition of Meter Accuracy 152.4.2 Meter Error Curves 152.4.3 Accuracy Requirements 172.5 Meter Classes 19Table of ConTenTs2.5.1 Conventional Meter Classes 192.5.2 New Meter Classes 212.6 Other Requirements 212.6.1 Materials 222.6.2 Flow and Water Quality 222.6.3 Operating Conditions 222.6.4 Pressure 232.6.5 Seals and Markings 23Chapter 3: Types of Water Meters 253.1 Introduction 253.2 Classification of Water Meters 253.3 Rotary Piston Meters 273.3.1 Mechanism 273.3.2 Characteristics 283.3.3 Application and Installation 30viii

Table of Contents3.4 Single Jet Meters 303.4.1 Mechanism 303.4.2 Characteristics 303.4.3 Application and Installation 323.5 Multijet Meters 323.5.1 Mechanism 323.5.2 Characteristics 323.5.3 Application and Installation 353.6 Woltmann Meters 353.6.1 Mechanism 353.6.2 Characteristics 353.6.3 Application and Installation 373.7 Combination Meters 393.7.1 Mechanism 393.7.2 Characteristics 393.7.3 Application and Installation 41Table of ConTenTs3.8 Electromagnetic Meters 423.8.1 Mechanism 423.8.2 Characteristics 433.8.3 Application and Installation 443.9 Ultrasonic Meters 453.9.1 Mechanism 453.9.2 Characteristics 453.9.3 Application and Installation 473.10 Comparison 49ix

Table of ContentsChapter 4: Water Meter Selection 514.1 Introduction 514.2 Meter Application 524.2.1 Where Should Meters be Installed? 524.2.2 Consumer Meters 544.2.3 Bulk Transfer Meters 564.2.4 Management Meters 564.3 Legal and Policy Requirements 574.3.1 Legal Requirements 574.3.2 Policy Requirements 594.4 Flow Range and Operating Conditions 624.4.1 Flow Range 624.4.2 Operating Conditions 664.5 Economic Considerations 684.5.1 Costs and Financial Benefits of Water Meters 684.5.2 Methods for Analysing Cost-efficiency 70Chapter 5: Getting the Most out of Water Meters:Operation and Maintenance 715.1 Introduction 715.2 Installation 735.3 Maintenance 755.4 Meter Testing 775.4.1 Test Methods 785.4.2 Large Meters 795.4.3 Domestic and Small Meters 795.5 Analysis 80x

IntroductionChapter 6: Meter Reading and Data Management 856.1 Introduction 856.2 Meter Reading Database 866.3 Meter Reading 886.3.1 Consumer Meters 886.3.2 Bulk Meters 926.4 Data Verification and Processing 92Chapter 7: Integrated Water Meter Management:Putting It All Together 957.1 Introduction 957.2 Strategic Planning 967.2.1 Metering Strategy 977.2.2 Water Tariff Design 1017.3 Information Management 1027.4 Asset Management 1037.5 Water Management 104InTroduCTIon7.5.1 Municipal Water Balance 1047.5.2 Water Demand Management 1057.5.3 Non-revenue Water Management 1067.6 Implementing an Integrated WaterMeter Management System 107List of References 113Appendix A: Glossary 117Appendix B: Organisations and Products 125Appendix C: Recommended Reading 127xi

Chapter 1InTroduCTIonxii

InTroduCTIon11.1 Why this Book?It is impossible for a municipality to manageits water resources without knowinghow much water it has and where the watergoes. This is where water meters play a criticallyimportant role: water meters are usedto measure how much raw water is takenfrom a resource such as a large dam, howmuch of this water leaves the water treatmentplant, how much is purchased frombulk suppliers or sold to other municipalities,how the water is distributed within thewater distribution system, and finally, howmuch of the water is delivered to individualconsumers. If water meters are not managedcorrectly, it can have a negative impact onthe income of a municipality. However, ifwater metering is approached correctly, itcan increase the net income of a municipality,while empowering staff to manage thedistribution system in the best possible way.Water metering is particularly important formunicipalities since it forms the basis formuch of their income through the sale ofwater to their consumers. In South Africa,like in many other countries, there is a legalimperative on municipalities to meter consumersand manage water losses in compliancewith legislation and standards.In South Africa, like in many other countries,there is a legal imperative on municipalities tometer consumers and manage water losses incompliance with legislation and standards.Many countries currently lack proper watermeter management, with many municipalitiesand bulk water suppliers not havingthe capacity to undertake and manageoptimal and integrated meter calibration,replacement, reading and informationmanagement systems. Often the dividedresponsibility between billing and meterman agement (typical of the institutionalarrangements within most municipalities)results in poor billing, incorrect informationcapture, and poor maintenance. This isfurther compounded by the fact that whereinitiatives of water demand managementand conservation are required, the data isnot easily accessible to the departmentsre sponsible for this task, leading to the frequentlack of integration between domesticand bulk water metering.The purpose of this book is to help addressthe need for better water meter managementby providing a practical introductionto the technical and managerial aspects ofwater meters. Since water metering affectsdifferent departments within a municipal-InTroduCTIon1

Chapter 1InTroduCTIonity, as well as various external parties, it isimportant to look at this topic from a holisticperspective, which is why the title refersto Integrated Water Meter Management.1.2 Why Water Metering?Water metering is an excellent applicationof the principle “to measure, is to know”,and knowledge of what is happening withthe water in a distribution system is the keyto properly managing this resource. Properapplication of an integrated water metermanagement strategy creates win-win conditionsfor all parties involved.While water metering has many direct andindirect benefits, there are four fundamentaldrivers for a comprehensive meteringprogramme 1 :• equity,• water efficiency and losses,• economic benefits, and• system management.1.2.1 Equity1.2.2 Water Efficiency and LossesWater supplied to consumers is taken fromthe environment, and thus using watermore efficiently has direct benefits for theenvironment. Areas with high populationdensity do not always have adequatenatural water resources, and require waterto be transferred from other areas at greatcost. In the worst cases, municipalities areforced to provide water intermittently withdevastating consequences for water quality,pipelines and water meters. Intermittentwater supply should be avoided at all cost.Metering shows the value of water to theconsumer and creates strong incentives forconsumers to use water more efficiently 2 . Infact, it has been shown that installing watermeters in itself reduces water consumption.Research conducted in the UK shows thatthe use of water in metered households is10-15% lower than in the unmetered ones 3 .This difference was found to be up to 50%in a Canadian study 4 .When water is particularly scarce, watermeters are essential for managing water demandand ensuring that consumers adhereto water restrictions.Comprehensive water metering providesan equitable basis for charging consumersbased on the amount of water that theyconsume. It makes consumers accountablefor their own water use and empowers themto influence how much they pay for thisservice. It also allows cross-subsidisationto be done fairly, and needy consumers toreceive a free basic amount of water.By comparing the readings on network andconsumer water meters, municipal engineersare able to estimate the level of waterlosses in a water supply system and identifyillegal connections. All water networks losesome water, but the level of losses has to becarefully monitored and managed to avoidthem reaching unacceptably high levels. Awell placed metering system in the distributionsystem will also assist technical staff inefficiently identifying the location of largeleaks.2

IntroductionNetwork and consumer meters are used incombination to estimate and manage thewater supply system, including revenue andlosses.1.2.3 Economic BenefitsMeasured consumption forms the basisof most water accounts, and thus affectsmunicipal revenue directly – water metersare the cash registers of water suppliers. Itfollows that a well managed and accuratewater meter system will improve water salesand thus municipal income. Many of thetechnical benefits of water meters, suchas accurately measuring municipal waterpurchases, reducing water losses, and identifyingand removing illegal connectionsalso have a positive impact on municipalfinances.Water meters are the cash registers of watersuppliers. They are essential for effective revenuemanagement.Water tariffs can be used to increasemunicipal income, cross-subsidise needyconsumers and manage water consumption.However, such a tariffs policy cannotbe implemented without a well establishedmetering system 4 .1.2.4 System ManagementOn a technical level, water meters are indispensiblefor knowing how much water isdistributed and where it goes. Water metersare used to measure water entering a watersupply system, whether from raw watersources, water treatment plants or bulk watersuppliers. Meters in the distribution networkmeasure where the water is transportedto, and finally, consumer meters are usedto measure how much water is delivered toeach metered consumer in the system.A pipe of a certain diameter can only carrya certain amount of flow, and thus pipeshave to be upgraded as water demandsincrease due to economic growth or newdevelopments. The same goes for municipalstorage tanks, pumps and other componentsof the network. To identify and planfor problems created by network components,technical staff uses water meter datato understand the water demand patterns inthe system and to project future demands.The demand data is critical to buildingaccurate computer models for simulatingwater distribution systems, investigatingreasons for hydraulic problems such as lowpressures, identifying future problems, andplanning expansions and improvements tothe system.A reliable and well run distribution systemwith a good income reflects positively onthe management of the system. It improvesthe public image of the municipality byproviding consumers with a better, morereliable service and accurate bills.The data obtained from a good meteringsystem allows management to takeinformed decisions on capital investments,maintenance, staffing and various otheraspects of the water supply system.The bottom line is that an integrated watermeter management system allows a municipalityto provide better services to thecommunity, while at the same time improvingits income.InTroduCTIon3

Chapter 1InTroduCTIon1.3 About this book1.3.1 Who Should Read this Book?The book is primarily aimed at municipalmanagers and staff who deal with anyaspect of water metering, whether froma practical, technical, financial, or purelymanagement perspective. The book doesnot require the reader to have a technicalbackground or prior knowledge of watermetering, although such knowledge willundoubtedly help with understanding theconcepts covered. The book will also beuseful to bulk water suppliers, governmentagencies, consultants and NGOs dealingwith any aspect of water metering or watermeter data, including:• High-level planning and management• Operational control and management• Maintenance and asset management• Treasury and billing systems• Water demand management• Water loss control• Water meter selection• Water meter purchasing, installation andreplacement• Refurbishment, testing and reading of watermeters.metering. The chapters and the way theyrelate to each other are shown diagrammaticallyin Figure 1-1.The first two chapters are critical to theunderstanding of the book and are recommendedfor all readers. This chapter givesthe background to the book and an overviewof the role and importance of watermetering. Chapter 2 introduces the basicsof water metering, including legislation andstandards, the basic components of watermeters, metrology and meter classes.Chapter 3 discusses the types of watermeters commonly used and how theyfunction. It is important reading for peopledealing with water meter selection, operationand maintenance. Other readers mightglance through the chapter and then referback to it as required.Chapters 4, 5 and 6 deal with importantaspects of water metering and can be readmore-or-less independently of each other,although reading all three chapters insequence is recommended. Chapter 4 dealswith water meter selection, Chapter 5 withthe life-cycle management of meters in thefield, and Chapter 6 with meter reading andthe management of meter reading data.The final Chapter (Chapter 7) concludesthe book with a discussion of how differentaspects of water metering can be integratedto get the maximum benefit for all partiesconcerned.1.3.2 How are the ChaptersOrganised?This book consists of seven chapters, eachdealing with a particular aspect of water1.3.3 A Few Tips for Getting Moreout of this BookThe illustrations, photographs anddiagrams used in the book were carefully4

IntroductionIntroduction(Chapter 1)Water meter basics(Chapter 2)Types of meters(Chapter 3)Meterselection(Chapter 4)Meter lifecyclemanagement(Chapter 5)Meter reading &data management(Chapter 6)Integrated watermeter management(Chapter 7)InTroduCTIonFigure 1-1 Chapter layout of this bookselected to assist with understanding theconcepts covered. Two types of text boxesare used in the text to highlight importantpoints made in the book, and to provideexamples or case studies:A number of appendixes with useful informationare provided in the back of thebook. Information provided includes:standards and other aspects of watermeters.• Meter suppliers and software for watermetering.• Recommended reading for more informationon specific aspects of water metering.• A glossary with important terms and abbreviationsused in water metering.• Organisations dealing with metrology,Text box highlightingimportantinformationText box giving anexample or casestudy5

WaTer MeTerbasICs22.1 IntroductionMillions of water meters are in use aroundthe world today, and every day thousandsof new meters are installed and old metersreplaced. The huge market for water metersmeans that many companies are involvedin the field, and that new technologies arecontinuously being introduced. Since mostwater meters are used to measure the volumesof water that are sold to consumers,they have to comply with strict legislationand standards that protect the consumerfrom exploitation. All of these factors canmake the seemingly simple task of selectingthe right water meter for a particularapplication a daunting prospect for aninexperienced person.To understand the field of water metering,it is important to start with thebasics. Thus the goal of this chapter is tointroduce the basic concepts, terms andstandards that apply to water meters. Thechapter covers the following:• A description of what a water meter is,and what components it consists of.While many different types of metersare available, they all have the same basiccomponents.• An overview of the legislation and standardsthat water meters typically have tocomply with.• An introduction to the field of water metermetrology. Metrology deals with watermeter accuracy, including the definitionof terms and standards. Certain wordshave very specific meanings in watermeter metrology, and it is important tobe familiar with these when dealing withwater meters.• The classes of water meters that areused to classify water meters in terms oftheir performance. New internationalstandards have been proposed that willeventually replace the conventionalstandards still in use in many countries.Both systems of meter classification arediscussed.• An overview of other requirements besidesaccuracy that water meters have tocomply with.WaTer MeTer basICs7

Chapter 2WaTer MeTer basICs2.2 Water Meters and TheirComponentsA water meter is a device that measuresthe volume of water that passes through it.Some documents distinguish between watermeters and flow meters based on the measuringmechanisms used by the meter. However,in this book the term water metersis used generically to refer to any type ofwater measuring device.A water meter is a device that measures thevolume of water that passes through it.All water meters consist of four basic components.These components are indicatedin a section through a typical water metershown in Figure 2-1, and consist of:1. A device to detect the flow passingthrough the meter, called the sensor. InFigure 2-1, the sensor consists of a paddlewheel that is rotated by the movementof the water passing through.2. A device that transmits the signal detectedby the sensor to the other parts ofthe meter, called the transducer or measurementtransducer. The transducer ofthe meter in Figure 2-1 consists of a spindlethat is rotated by the paddle wheel.3. A device to keep track of the flow thathas passed through the meter, called thecounter. The counter of the meter in Figure2-1 consists of a set of counter wheelsor numbered discs, similar to the odometerof a car.4. A device to communicate the readingsto the meter reader, called the indicator.The indicator of the meter in Figure 2-1consists of the numbers on the counterwheels that are visible on the face of themeter.All water meters consist of four basic components: a sensor to detect the flow, a transducer totransmit the flow signal, a counter to keep track of the total volume having passed through the meter,and an indicator to display the meter reading.IndicatorCounterTransducerSensorFigure 2-1Section through awater meter showingthe sensor, transducer,counter andindicator (meter suppliedby Sensus)8

Water Meter BasicsWhile the four basic components are alwayspresent in any water meter, many differenttypes of devices are used for each component.There are also many additional componentsthat may be installed on a watermeter to perform specific functions. Thusit is necessary to look at the meter componentsin more detail.2.2.1 SensorThe sensor or measuring element is thedevice in a water meter that detects the flowpassing through the meter. The types ofwater meters (discussed in Chapter 3) aremainly distinguished by the mechanismsused by their sensors.Some sensors can detect the volume ofwater passing through the meter directly bycounting off little ‘packets’ of water passingthrough. Meters with these sensors arecalled volumetric or positive displacementmeters. However, most types of sensorsdon’t measure the volume directly, but measurethe flow velocity and then convert thevelocity into a volume. Meters using thesesensors are called inferential or velocity meters(they infer the volume from the velocitymeasurement).Different positive displacement sensors areused. The most common types use a rotatingdisc, but oscillating pistons are alsofrequently used. Nutating disc meters arevolumetric meters popular in the USA, butare not used much in Europe or Africa. Anexample of a volumetric sensor is shown inFigure 2-2.Volumetric meter. A flow meter with asensor that measures the volume of waterpassing through it directly by counting off‘packets’ of water. It is also called a positivedisplacement meter.Velocity meter. A flow meter with a sensorthat measures the velocity of the water passingthrough it, and then converts the velocityinto a volume. It is also called an inferential orvelocity meter.The sensors used by inferential meters typicallyconsist of rotating impellers with radialor helical vanes as shown in Figure 2-3.Magnetic and ultrasonic meters are alsoclassified as inferential meters, even thoughWaTer MeTer basICsFigure 2-2 A rotating positive displacementmeter sensor (sensor provided by Elster Kent)Figure 2-3 Radial and helical vane impellers9

Chapter 2they don’t employ mechanical moving partsin their sensors.2.2.2 TransducerOther types of transducers employ electricalsignals, which allow the signal to be transmittedto a counter located in a different location.WaTer MeTer basICsThe transducer or measurement transducertransfers the signal picked up by the sensorto the rest of the meter. The simplest transducerconsists of a thin mechanical spindlethat is rotated by the sensor, such as theone shown in Figure 2-1. A disadvantageof this type of transducer is that it can generatefriction, reducing the meter accuracyand causing wear in the meter over time. Itis also very difficult to seal off water aroundthe spindle if the transducer has to transmitthe measurement signal into a dry chamberwhere parts of the meter is housed. (Wetand dry dial meters are discussed in Section2.2.5.)A type of transducer that is frequently usedin meters with dry compartments uses smallmagnets to transmit the signal into the drychamber. Meters using magnetic transducersrequire special protection to ensure thatexternal magnetic fields do not interferewith the meter reading. Examples of directand magnetic transducers are illustrated inFigure 2-4.2.2.3 CounterThe counter or calculator is the part of ameter that accumulates the flow readings itreceives via the transducer. It holds the totalvolume of water that has passed throughthe meter since its manufacture, just likethe odometer of a car holds the total distancethat a car has travelled. In fact, mostcounters use the same rotating disc countersused for the odometers of cars, althoughother types of gear mechanisms are alsosometimes used. An example of a rotatingdisc counter is shown in Figure 2-5.In some cases, the meter counter consists ofan electronic device that keeps the volumereading of the meter in its internal memory.2.2.4 IndicatorThe indicator is the part of the meter thatdisplays the measurement to a meter reader.When a rotating disc counter is used, theindicator simply consists of the numbers onthe discs that are displayed on the face ofWet dialDirecttransducerDry dialMagnetictransducer(a)(b)Figure 2-4 Diagrams of a) direct transducer in an open wet dial meter and b) a magnetic transducer ina sealed dry dial meter.10

Water Meter Basicsis known as the verification scale interval.Figure 2-5 A rotating disc calculatorthe meter. Other types of indicators thatare used include rotating pointers and electronicdisplays. Examples of meter indicatorsare shown in Figure 2-6.The indicator and counter are sometimescontained in a sealed, dry chamber and atother times in a wet chamber – one that isfilled with water. A discussion of wet anddry dial meters follows in Section 2.2.5.The indicator should be supplied with adark cover to prevent algae from growing.The indicator should have a transparentwindow and should show the meter readingin an easily readable, reliable and clearway. The element on the indicator that displaysthe lowest value is called the control element,and the interval used on this elementIn most countries, including South Africa,water meters are only allowed to displaytheir readings in cubic meters (m 3 ) as theunit of measurement. (Note that 1 cubicmeter is equal to 1000 litres of water.) Twoclearly contrasting colours (for exampleblack and red) have to be used for the cubicmeter values and fractions of a cubic meteras shown in Figure 2-6(a). Where separatedials or pointers are used, these have tobe clearly marked with a multiplying factorto show the units they are measuring, asshown in Figure 2-6(b).2.2.5 Wet and Dry Dial MetersThe counter and indicator of a water metermay be housed in a dry or wet (water-filled)housing. In dry dial meters, the counter andindicator are placed in a sealed chamber. Ahigh level of water-tightness is ensured whenthe chamber carries an IP68 rating (from thestandard IEC 60529 6 ), and are sometimescalled extra-dry chambers. However, it is importantto note for how long the meters weresubjected to the IP68 test – the longer thetest, the better the seal. Dry dial meters oftenuse magnetic transducers, and thus requireWaTer MeTer basICsFigure 2-6 Examples ofmeter indicators(a)(b)11

Chapter 2WaTer MeTer basICsspecial protection against magnetic fieldsthat may interfere with the meter reading.An advantage of dry dial meters is thattheir counters and indicators do not comeinto direct contact with the water, and arethus protected from suspended particlesthat may create problems due to settling orobstruction of the counter gears. In addition,the transparent window covering thedial doesn’t have to be strong enough tosustain the water pressure in the network,which reduces the cost of the meter. Onthe negative side, if any damp gets past theseal, condensation can form on the insideof the meter window, making the meterimpossible to read. In some cases, metersare provided with a mechanism to removedamp from the inside of the window.In wet dial meters, the chamber housing thecounter and indicator is either filled withwater from the network (i.e. water maymove between the counter and sensor partsof the meter), or housed in a sealed chamberthat is filled with a mixture of waterand glycerine (to stop algae from growing).A benefit of wet dial meters is that dampis not a problem. However, open wet dialmeters are not suitable for dirty water, orwater with high iron content. Dirt from thewater can get stuck in the counter mechanismcausing the meter to malfunction. Inaddition, the transparent window housingof an open wet dial meter has to be strongenough to withstand the full pressure in thedistribution network, adding to the cost ofthese meters. Better quality meters use 14mm armour plate glass lenses.2.2.6 Additional Meter ComponentsMeters can have various additional componentsto improve their accuracy or makethem easier to use. For instance, an adjustmentdevice may be fitted that allows themanufacturer to make final calibrationadjustments to the meter. Other additionalcomponents may allow data to be storedin the meter, show the water price, or seta fixed volume to supply before the flow isautomatically discontinued. Some metershave mechanisms to transfer data electronicallyto (and even from) data loggers orremote stations.Most meters can be logged using additionalequipment. This is an important functionsince it allows the flow through the meterto be recorded and analysed, and for themeter to be fitted with an automatic meterreading system at a later stage if desired.Special signal transducers are required totransmit the meter readings to a logger unitthat stores the data. The transducer receivesan optical or magnetic pulse (signal) fromthe meter, and sends it through to the logger.Such a pulse is generated each time acertain volume of water has passed throughthe meter. The value of the pulse dependson the meter, and can vary from fractionsof a litre to several litres. Another importantissue when logging water meters is to ensurethat the logger can distinguish betweenforward and reverse flow when flow reversalis likely to occur. Finally, it is a good ideato verify the volume registered by the loggeragainst the volume accumulated by themeter over the same time period to ensurethat all pulses were correctly logged.Its is important to note that additionalmeter components, such as electronics or12

Water Meter Basicsprepaid systems, cannot operate independentlyof the meter.2.3 Legislation and StandardsMost water meters are used to measurewater that is sold to consumers, and thusthey have to comply with strict legislationand standards that are local to the countryin which the meters are used. This sectionincludes the South African legislation andstandards that relate to water metering, aswell as the most common internationalstandards.have to be verified before installation and atintervals specified by the Act. The verificationhas to be done by a qualified andregistered Verification Officer in a SANASAccredited Test Laboratory in terms ofSANS 10378 4 .Water meters larger than 100 mm cannotbe tested in South Africa and many othercountries since large enough testing facilitiesare not available. However, it is stillrequired that the meter undergoes certaintests at the SABS, and that the suppliersprovide a verified accuracy curve for themeter.It is a legal requirement that each consumerwater meter installed in South Africa mustcomply with the standard SANS 1529, andmust be tested by a registered verificationofficer in an accredited test laboratory. Anymeter in the field that does not comply withthe accuracy requirements of SANS 1529 mustimmediately be withdrawn from service.2.3.1 LegislationThe main laws that have a bearing on watermetering in South Africa are the MunicipalServices Act 1 and the Trade Metrology Act 2 .Municipalities are required by law to meterall consumers. 3The South African Trade Metrology Actrequires consumer water meters of sizes 15to 100 mm to comply with the requirementsof SANS 1529 4 and that municipalitiesmust ensure that all meters under theircontrol are kept in a verifiable condition atall times. This means that municipal metersAny meter that becomes defective, or doesnot comply with the accuracy requirementsspecified in SANS 1529, must beimmediately withdrawn from service.2.3.2 StandardsInternational water meter standards tendto be very similar on major issues such asmeter accuracy and classification (exceptfor the US standards, which tend to followtheir own approach). However, in recentyears most international standards haveundergone major revisions that have substantiallychanged the way water meters areclassified (see Section 2.5 for more details).Many countries have not yet adopted thenew standards, and in any case it will takemany decades before the new standards becomethe norm due to the long service livesof many meters currently installed. Theapproach followed in this book is to usethe conventional meter standards, but toinclude discussions of the new standards toallow the reader to understand both systems.WaTer MeTer basICs13

Chapter 2WaTer MeTer basICsAn example of the conventional meterstandards can be found in the documentSANS 1529: Water Meters for Cold PotableWater, which currently consist of four parts(the numbering of the parts was not donesequentially to allow more parts to be addedin future):• Part 1: Metrological characteristics of mechanicalwater meters of nominal bore notexceeding 100 mm.• Part 3: Physical dimensions.• Part 4: Mechanical meters of nominal boreexceeding 100 mm but not exceeding 800mm.• Part 9: Requirements for electronic indicatorsused with mechanical water meters,electronic water meters and electronic prepaymentwater measuring systems.The new international standards are availablein a number of documents, with verysimilar requirements (efforts are currentlyunderway to merge them into a single standard).The main international standards are:• International Organization of Legal Metrology:OIML R49: Water meters intendedfor the metering of cold potable water andhot water 6 . Note that it uses the Frenchacronym OIML even for the English languageacronym.• International Organization for Standardization:ISO 4064 Measurement of waterflow in fully charged closed conduits —Meters for cold potable water and hot water 7 .• European Union standard: EN 14154Water meters 8 . This standard was developedin response to Directive 2004/22/EC 9 ofthe European Parliament, called the MeasurementInstruments Directive (MID).As a result, the acronym MID is oftenused to refer to the European standard.Like the SANS standard, the internationalstandards are often made up of a number ofparts dealing with different aspects of watermetering. The standards published by theOIML are available as a free download fromtheir website www.oiml.org.2.4 MetrologyIt is important to understand that any measurement,irrespective of what is measuredor how carefully the measurement is taken,has a limited accuracy. In other words, anymeasurement includes some degree of error,and thus there is some level of uncertaintyincluded in the measurement.Metrology is the science of measurement.Metrology is the study of measurementaccuracy, including how to determine theaccuracy of a given measurement deviceand what sort of accuracy is requiredwhen measuring different things. In thebroadest sense, metrology is the science ofmeasurement.There are different branches of metrology,such as for scientific measurements orindustrial processes. The branch of metrologythat is most important for water metersis called legal metrology, and deals with thelegal requirements of measurements andmeasuring instruments in order to protectconsumers and ensure fair trade.It is important to understand and correctlyuse the metrology terms when dealing withwater meters.14

Water Meter Basics2.4.1 Definition of Meter AccuracyThe volume of water that passes througha water meter is called the actual volume,or V a. However, since no meter is 100%accurate, the meter will not register allthe water passing through it, but show areading or indicated volume (V i), which isnormally slightly lower or higher than theactual volume. The difference between theindicated volume and actual volume (V i-V a) is called the meter error. When the erroris expressed as a fraction (percentage) of theactual volume, it is called the relative error.New water meters must be tested undercontrolled conditions in highly accuratetesting laboratories. The meter error determinedin this way is called the intrinsicerror. The actual meter error will be differentfrom the intrinsic error, since fieldconditions can vary greatly from those ina laboratory, and accuracy reduces withmeter age.2.4.2 Meter Error CurvesWater meters are designed for a specificflow rate, which is called the permanent flowrate or q p(Q 3in the new international standards).The meter should be able to workat the permanent flow rate (or a lower flowActual volume, V a: The total volume of water passing through the water meter, irrespective of howlong this took.Indicated volume, V i: The volume of water indicated by the meter. For a perfect meter, this will beequal to the actual volume. However, most meters will indicate slightly higher or lower readings.Error: The difference between the indicated volume and the actual volume, or V i– V a.Relative error: The error divided by the actual volume.Permanent flow rate (q p ), is the flow rate forwhich the meter is designed.Intrinsic error: The meter error determined under controlled conditions in a highly accurate testinglaboratory accredited for this purpose.WaTer MeTer basICsExample of a meter accuracy calculation.A water meter has an initial reading of 123.456 m 3 . After exactly 200 l of water has passed throughthe meter over a period of 5 minutes, the meter reading is changed to 123.654 m 3 . To determinethe flow rate through the meter, and the relative error of the meter at this flow rate:Actual volume V a= 200 l.Actual flow rate = actual volume / time = 200/5 = 40 l/min, or 2 400 l/h.Indicated volume V i= 123.654 – 123.456 = 0.198 m 3 , or 198 l.Error = V i– V a= -2 l, i.e. the meter under-registered the volume by 2 l.Relative error = error / actual volume = -2/200 = -1%. This means the meter under-registers theflow by 1% at a flow rate of 2 400 l/h.15

Chapter 2WaTer MeTer basICsrate) continuously for its design life withoutexceeding the permissible error.Although a meter is designed for the permanentflow rate, the actual flow througha meter is not constant, but varies a greatdeal. Thus water meters should not onlybe accurate at the permanent flow rate, butover a wide range of flow rates.The relative error of a meter is not the samefor the full flow range of a water meter. Forinstance, mechanical meters tend to underregisterat low flow rates and over-registerat higher flow rates. In addition, as watermeters age they tend to reduce in accuracyand generally under-register more.It is useful to draw a graph of a meter’srelative error as a function of the flow ratethrough it: this curve is called the meter’serror curve. An example of a typical metererror curve for an inferential meter is shownin Figure 2-7.To understand the accuracy curve better,consider a mechanical flow meter installedin a pipe with the supply valve completelyclosed, so that no flow occurs through themeter. Now the valve is opened very slightlyto allow a very small flow to occur in thepipe. As the water moves across the metersensor, it pushes against the sensor in anattempt to move it. However, the sensoris held back by friction forces, and at verysmall flow rates the water cannot overcomethese friction forces to get the sensor moving.Thus the sensor remains static and themeter doesn’t register the small flow passingthrough it.If the flow is now gradually increased further,a point is reached where the water isjust able to get the sensor moving, and forthe meter to start registering a flow. Thisflow rate, the smallest that the meter is ableto register, is called the starting flow rateq start. It can be seen from Figure 2-7 thatthe meter under-registration error at thestarting flow rate is large, which means thata lot of the flow through the meter will notbe registered.Relative Relative errorUnder registration Over registration0%0 q startq pq Flow rateasFigure 2-7 Typical error curve for an inferential meter16

Water Meter BasicsAs the flow rate increases, the meter error reducesand becomes positive, i.e. it over-registersthe flow. The positive error increasesfor a while before it reduces again (causinga bulge in the accuracy curve) and stabilisesclose to the zero-error line. This stable zonecontinues past the permanent flow rateand represents the ideal flow rate where themeter will produce the best results.While the meter is designed to operate q pcontinuously at the permanent flow rate, it isable to handle higher flows without detrimentto the meter, as long as these higherflows last for only short periods at a time.The overload flow rate q s(Q 4in the newinternational standards) is shown on thevery right of the error curve in Figure 2-7,and should never be exceeded. If the flowrate through the meter is greater than theoverload flow rate, even for a short period,the meter may sustain permanent damage.To define this point, the overload flow rateis defined as the highest flow rate at whicha meter can operate for a short period withoutsustaining permanent damage.Starting flow rate or q start: The lowest flowrate at which the meter is able to register flowpassing through it.Overload flow rate, q s: The highest flowrate at which the meter should be able tooperate (within the required accuracy) for ashort period without permanent damage to itsaccuracy.2.4.3 Accuracy RequirementsThe standards that specify the requiredaccuracy of water meters have to take thetypical accuracy curves of meters (Figure2-7) into account. Thus they specify themaximum permissible error (MPE) of ameter as an outline or ‘envelope’ as shownin Figure 2-8. The maximum permissibleerror is the largest relative error that is allowed,irrespective of whether the error ispositive or negative.The maximum permissible error envelopeis divided into two zones called the lowerand upper zones respectively, and the meteris allowed to have a larger error in the lowerzone than the upper zone. SANS 1529specifies a minimum permissible relativeerror of 5% in the lower zone, and 2% inthe upper zone as indicated in Figure 2-8.The start of the lower zone, or the maximumflow rate at which the relative metererror should be less than 5%, is called theminimum flow rate q min(Q 1in the newinternational standards). The start of theupper zone, or the maximum flow rate atwhich the relative meter error should be lessthan 2%, is called the transitional flow rateq t(Q 2in the new international standards).The upper zone continues up to the specifiedoverload flow rate q s.Simply put, the meter accuracy curve mustMaximum permissible error (MPE): Themaximum allowable relative error, irrespectiveof whether the error is positive ornegative.Minimum flow rate, q min: The lowest flowrate at which the water meter is required tooperate within the maximum permissibleerror.Transitional flow rate, q t: A flow ratebetween the minimum flow rate and permanentflow rate at which the maximumpermissible error of the meter is reduced.WaTer MeTer basICs17

Chapter 2Lower zoneUpper zone5%Relative error2%0%-2%-5%q min q t q p Flow rateq sWaTer MeTer basICsFigure 2-8 SANS 1529 requirements for meter accuracyLower zoneUpper zone5%Relative error2%0%-2%-5%dabcq min q t q p Flow rateq sFigure 2-9 Examples of meters meeting the SANS 1529 standard (a and b) and not meeting thestandard (c and d)18

Water Meter Basicsplot fully inside the specified accuracy envelopeto comply with the standard. If anypart of it falls outside the accuracy envelope,the meter is rejected. Figure 2-9 showsfour meter accuracy curves plotted on theSANS 1529 requirements. Meters a andb fall fully within the accuracy envelope,and will thus be accepted. However, metersc and d have parts that fall outside the envelopeand will be rejected.It is important to realise that error envelopesdefined by the standards are minimumrequirements. The actual values for ameter can be (and mostly are) better thanthose specified by the standards.2.5 Meter ClassesMeter classes are used to classify metersaccording to their accuracy performance.As discussed in Section 2.3.2, the conventionalmeter standards are being replaced inmany countries by new standards that usea completely different approach to definingmeter classes. However, the conventionalstandards will still be in use for many yearseven in those countries that adopt the newstandards, and thus both metering classsystems are discussed.2.5.1 Conventional Meter ClassesConventionally four classes of meters aredefined and denoted by the letters A, B, Cand D. The accuracy requirements are thesame for all four classes, namely a maximumpermissible error of 5% in the lowerflow zone and 2% in the upper flow zone.The differences between the classes lie inhow high the transitional and minimumflow rates are allowed to be in relation tothe permanent flow rate. Class A has thelowest performance and class D the highestperformance. The requirements for thehighest allowable minimum and transitionalflow rates are given in Table 2-1 formeters with permanent flow rates up to 10m 3 /h. Table 2-2 does the same for meterswith permanent flow rates larger than 10m 3 /h. Note that class A meters may not beused for trade purposes, i.e. at consumerconnections.In all cases, the overload flow rate of ameter has to be at least twice its permanentflow rate.When water meters are taken out of thefield and tested, they are allowed to showlarger errors than new meters. The maximumpermissible errors for these metersWaTer MeTer basICsTable 2-1 Meter classes defined by SABS 1529 for permanent flow rates up to 10 m 3 /hMeter class Minimum flow rate (q min) Transitional flow rate (q t)IncreasingstringencyA 0.04 q p0.10 q pB 0.02 q p0.08 q pC 0.01 q p0.015 q pD 0.0075 q p0.0115 q p19

Chapter 2Example: Consider a meter with a permanent flow rate of 1 m 3 /h or 1 000 l/h. The minimumaccuracy requirements for this meter is shown in Figure 2-10 for classes A to D.q min40 l/hq tq p100 l/h 1000 l/hq s2000 l/hClass AWaTer MeTer basICsq minq min20 l/hq tq t80 l/hq p1000 l/hq pq s2000 l/hq sClass BClass C10 l/h15 l/h1000 l/h2000 l/hq minq tq pq sClass D7.5 l/h11.5 l/h1000 l/h2000 l/hFigure 2-10 SANS1052 accuracy requirements for a meter with a permanent flow rate of1 000 l/h for classes A to D.20

Water Meter BasicsTable 2-2 Meter classes defined by SABS 1529 for flow rates exceeding 10 m 3 /hMeter Classes Minimum flow rate (q min) Transitional flow rate (q t)IncreasingstringencyA 0.08 q p0.3 q pB 0.03 q p0.2 q pC 0.006 q p0.015 q pare 8% in the lower flow zone and 3.5% inthe higher flow zone. Meters not satisfyingthese requirements may not be reinstalledin the field.2.5.2 New Meter ClassesThe new international standards such asOIML R49 5 follow a completely differentapproach to defining meter classes. Theyuse the same definitions for the minimum,transitional, permanent and overload flowrates,but instead of using the symbols q min,q t, q pand q srespectively for these parameters,the new standards use the symbols Q 1,Q 2, Q 3and Q 4.For any meter, the permanent flow rate isspecified first. The minimum flow rate isthen determined by using one of the followingvalues for the ratio of the permanentflow rate to the minimum flow rate (Q 3/Q 1):1031.510031512.540125400165016050020632006302580250800This ratio defines the meter accuracy range,and is often used with the letter R to describethe meter. For instance, a meter witha Q 3to Q 1ratio of 160 will be described asa R160 meter.The ratio of the transitional flow rate to theminimum flow rate Q 2/Q 1is fixed at 1.6.Finally the ratio of overload flow rate to permanentflow rate Q 4/Q 3has to be 1.25.The OIML standard specifies two meterclasses (Classes 1 and 2) based on themaximum permissible error, rather thanthe width of the flow zones. Class 1 has thehighest accuracy requirements with a maximumpermissible error of 3% in the lowerzone and 1% in the upper zone. For Class2 meters, the maximum permissible error is5% in the lower zone and 2% in the higherzone. These requirements are summarisedin Table 2-3.Only meters with permanent flow rateslarger or equal to 100 m 3 /h may be Class 1meters (although these meters may also beClass 2 meters). Meters with flow rates lessthan 100 m 3 /h may only be Class 2 meters.2.6 Other RequirementsThe South African standards have manyother requirements with which watermeters must comply. Some of these requirementsare given in this section to providean overview of the standards. However, itis important to consult the latest edition ofWaTer MeTer basICs21

Chapter 2Table 2-3 Meter classes defined by IOML R49Meter ClassApplicable toMaximum permissible errorLower zoneHigher zone1 Only meters with Q p >100 m 3 /h. 3% 1%2All meters with Q p < 100 m 3 /h.May be applied to meters with Q p > 100 m 3 /h5% 2%WaTer MeTer basICsthe standards first hand when importantmetering decisions are made.2.6.1 MaterialsWater meters may only be constructed ofcopper alloy, plastics and stainless steel,except for 40 mm and larger Woltmannmeters, which are allowed to use other ferrousmaterials. Parts of water meters thatare in contact with the water are requiredto be of sufficient standard or coated toprevent corrosion or leaching of chemicalsfrom the material into the water. In particular,certain countries (including SouthAfrica) require brass components that comeinto contact with the water to be dezincificationresistant (DZR). Plastic meter partsshould be made of virgin plastic and shouldnot be exposed to the sun. Thus exposedplastic meters should always be installed inmeter boxes.2.6.2 Flow and Water QualityAcceleration devices, which are used toincrease the speed of a meter at flow ratesbelow the minimum flow rate to reduceunder-registration, are not allowed.All meters, except Woltmann meters andsingle jet meters of 50 mm and larger,should have an integral strainer or filter toprotect its working parts from damage.Meters should be able to withstand accidentalflow reversal and have to indicatethe reverse flow, although the reverse flowdoesn’t have to be measured at the normalmeter accuracy.2.6.3 Operating ConditionsWater meters are tested under controlledlaboratory conditions, called reference conditions.However, the actual conditions underwhich a meter works in the field, includingflow rate, temperature, pressure, humidityand electromagnetic interference, canbe significantly different and are called themetering conditions.The range of conditions under which awater meter is required to operate withinits maximum permissible errors is called therated operating conditions, and the extremeconditions under which a meter should beable to operate outside of its required accuracy(but without damage or permanentdeterioration in its performance) are calledthe limiting conditions.22

Water Meter BasicsValues for the maximum admissible pressure,minimum admissible temperature andmaximum admissible temperature of metershave to be specified by manufacturers.• Manufacturer• Permanent flow rate in m 3 /h• Serial number2.6.4 PressureThe average pressure that a meter operatesunder is called the working pressure. SANS1529 assumes the working pressure to be1 600 kPa unless otherwise specified. SANS1529 specifies that meters have to be testedat pressures three times the working pressure,but not lower than 4 000 kPa and nothigher than 6 000 kPa.Water flowing through the meter will undergoa certain pressure loss, which will varywith flow rate and the type of meter. Theallowed pressure loss through a meter isspecified in groups by SANS 1529 as shownin table 2-4.Table 2-4 Pressure loss groups defined bySANS 1529GroupP100P60P30P10Maximumpressure loss100 kPa60 kPa30 kPa10 kPa• Direction of flow (i.e. an arrow)• Meters for which parts can be exchangedin the field must have a mark on the bodyto indicate that the body has been approvedfor this purpose• South African approval number (referringto type approval of meter model)• Metrological class A, B, C or D• If the meter is only suitable for horizontalor vertical installation, the letter H or Vrespectively should be displayed• Working pressure if other than 1 600 kPa• The pressure loss class.WaTer MeTer basICs2.6.5 Seals and markingsMeters must be sealed in the factory afterassembly and verification so that it is impossibleto tamper with the meter withoutvisible damage to the meter or seal.The following markings should be added tothe meter body:23

Types ofWaTer MeTers33.1 IntroductionA large number of water meters are availableon the market today, and it can be anoverwhelming task to select the right meterfor a given application. Fortunately, whendealing with water distribution systems, itis possible to substantially narrow down theoptions.The purpose of this chapter is to introducethe types of water meters that are commonlyused in water distribution systems.3.2 Classification of Water MetersWater meters are generally classified basedon the mechanism used by the meter tomeasure the flow passing through it. Aclassification of the meters discussed in thisbook, and the sections in which they arecovered, is shown in Figure 3-1.through the meter using electromagneticprinciples or ultrasound waves. Electromagneticand ultrasonic meters are discussed inSections 3.8 and 3.9 respectively.Mechanical meters make up the vast majorityof meters used in water distributionsystems. For instance, mechanical metersaccount for more than 99% meters installedin Tshwane 1 . Ultrasonic and electromagneticmeters are only applied in specialcases, such as in very large pipes or where aparticularly high accuracy is required.Mechanical meters are categorised intovolumetric, inferential and combinationmeters. Volumetric meters directly measurethe volume of flow passing through them.Most volumetric meters use a rotating diskto measure the flow, and are known as rotatingpiston meters. These meters are discussedin Section 3.3.Types of WaTer MeTersThe first important distinction is whetherthe meter mechanism is based on mechanical,electromagnetic or ultrasonic principles.Mechanical meters have moving parts thatdetect the flow, such as a piston or impeller.Electromagnetic and ultrasonic metershave no moving parts, but detect the flowInferential meters do not measure the volumeof water passing through them directly,but infer the volumetric flow rate fromthe velocity of the water. Two categoriesof inferential meters are commonly used:those meters using a radial vane and thoseusing a helical vane impeller. Radial vane25

Chapter 3impeller meters are further classified intosingle jet and multijet (short for multiplejet) meters. Helical vane meters are alsocalled Woltmann meters, and use a propellerlikevane to pick up the water velocity.Single jet, multijet and Woltmann metersare discussed in Sections 3.4, 3.5 and 3.6respectively.Combination meters don’t use a uniquemechanism to measure the flow, but areWater metersMechanicalElectromagnetic(Section 3.8)Ultrasonic(Section 3.9)Types of WaTer MeTersVolumetricRotary piston(Section 3.3)InferentialRadial vaneCombination(Section 3.7)Helical vaneSingle jet(Section 3.4)Multijet(Section 3.5)Woltmann(Section 3.6)Figure 3-1 Classification of the common water meters covered in this chapter.26

Types of Water Metersmade up of two meters of different diametersthat are combined to measure a particularlywide range of flow. They are discussedin Section 3.7.3.3 Rotary Piston Meters3.3.1 MechanismRotary piston meters are positive displacementmeters that use a rotating cylindricalpiston to measure ‘packets’ of water movingfrom the inlet to the outlet of the meter. Asimplified illustration of the meter mechanismis shown in Figure 3-2. (The figureshows a solid piston, but in actual metersthe inside of the piston is hollow, and isused to carry more water.) However, themechanism remains the same.The cylindrical piston sits at an offset fromthe centre of the meter chamber, and dividesthe chamber into two compartmentsthat are isolated from each other. The cylindricalpiston rotates in a clockwise directionalong the edge of the meter chamber.In Figure 3-2(a), the piston has just movedacross the meter inlet to create a small compartmentwhere water is entering the meter(shown in light blue). The second compartment(shown in dark blue) is connected tothe meter outlet. As the cylindrical pistonmoves along the meter chamber edge ina clockwise direction, the outlet chamberdecreases in size, pushing water out throughthe outlet. At the same time the inlet compartmentincreases in size, and more waterenters the meter through the inlet.Figures 3-2(b) to (e) shows the progressionof the piston along the meter chamberedge. In Figure 3-2(e), both the inlet andoutlet are closed simultaneously, showingthe ‘packet’ of water that is moved from theinlet to the outlet each time the cylindricalpiston has made a full rotation. Theprocess in Figure 3-2(a) to (e) is repeated,and since each rotation transports exactlythe same volume of water, the volume passingthrough the meter can be accuratelydetermined by counting the number ofrotations.Types of WaTer MeTersDivision plateOutletInlet(a) (b) (c) (d) (e)Figure 3-2 A simplified illustration of the mechanism of rotary piston meter. The rotary piston moves ina clockwise direction.27

Chapter 33.3.2 CharacteristicsPositive displacement meters are popular fortheir combination of accuracy, long life andmoderate cost, and are the meter of choicefor most domestic applications 2 .Rotary piston meters come in many differentshapes and sizes as can be seen fromFigure 3-3. The meter housing is typicallymade out of brass or plastic, and the internalcomponents from plastic. Wet and drydials are used. It is important to note thatplastic body meters have to be installed invalve chambers to protect them from thesun.Rotating piston meters are sensitive tosand or other suspended solids in the waterthat can get stuck between the piston andTypes of WaTer MeTersFigure 3-3 Examples of rotary piston meters. (meters provided by Elster Kent, Itron and Sensus)28

Types of Water Meterschamber wall, jamming the meter. Thus itis important that these meters should onlybe installed in systems with very good waterquality, and they should always be providedwith built-in strainers.A rotating piston meter in good workingorder is highly accurate, and it is the onlytype of domestic water meter available inClass D. These meters are very sensitiveto low flows and are especially suitable forapplications where low flow rates or on-siteIf air is forced through the meter, themetering error can be quite severe and thewear on the moving parts of the meter isincreased substantially. It is recommendedthat an air valve is installed at an elevatedpoint upstream of the meter to remove airfrom the system.The typical metrological characteristics ofcommonly used rotating piston meters aresummarised in Table 3-1.Table 3-1 Metrological characteristics of common rotating piston metersClass Size (mm) q start(l/h) q min(l/h) q t(l/h) q p(l/h) q s(l/h)C 15 1 10 15 1000 2000C 15 3 15 22.5 1500 3000C 20 4 25 37.5 2500 5000C 25 6 35 52.5 3500 7000C 30 11 50 75 5 000 10 000C 40 18 100 150 10 000 20 000D 15 3 7.5 11.5 1000 2000D 20 6 18.75 28.75 2500 5000Note: These are typical values supplied by meter manufacturers, and thus may be better (but notworse) than the requirements of SANS 1529.Types of WaTer MeTersleakage frequently occur, such as domesticconsumers.The accuracy of rotating piston meters isdependent on water not leaking past thepiston from the inlet to the outlet compartment.It is therefore important that they aremanufactured to strict tolerances. As rotatingpiston metres age and wear through use,water is able to leak past the piston moreeasily, and thus the meters tend to underregisterwith age.Rotating piston meters have been in use fordecades, and are very popular for domesticapplications throughout the world. Theyhave excellent sensitivity at low flow rates,and remain accurate irrespective of installationposition. The main disadvantagesof rotating piston meters are that they aresensitive to suspended solids in the water,prone to relatively high pressure losses, andthat they can be more bulky and expensivethan other meter types.29

Chapter 3Types of WaTer MeTers3.3.3 Application and InstallationRotating piston meters are commonly usedfor domestic meters up to a diameter of25 mm. The meter body must show anarrow indicating the flow direction throughthe meter, and it is very important toinstall correctly. Volumetric meters are notsensitive to the velocity profile of the flowentering the meter, and can be installed invirtually any position without significantloss in accuracy. They can also be placedclose to bends or pumps.3.4 Single Jet Meters3.4.1 MechanismSingle jet meters are inferential meters thatuse a single flow stream or jet to move thesensor, which consists of an impeller withradial vanes (also called a fan wheel). Therotation speed of the impeller is convertedinto a flow rate, which is registered on themeter. A cutaway view of a single jet meteris shown in Figure 3-4.3.4.2 CharacteristicsIt is critical for the accuracy of a single jetmeter that the path of the water throughthe meter is precisely controlled. Thus theinside of the meter has to be manufacturedto strict tolerances. Traditionally the meterchamber is made out of brass, but plasticsare also becoming popular. Brass chambersmake the meter expensive, especiallyin larger diameters. Single jet meters arethus mostly used in the size range of 15 to40 mm. Examples of single jet meters areshown in Figure 3-5.The typical metrological characteristics ofcommonly used single jet meters are summarisedin Table 3-2.Figure 3-4 Cutawayview of a a singlejet meter (meterprovided by Itron)30

Types of Water MetersTypes of WaTer MeTersFigure 3-5 Examples of single jet meters (meters provided by Sensus and Itron)Single jet meters may be affected bydisturbances in the velocity profile, but inpractice they are not very sensitive to disturbanceslike bends close to the meter. Morecritical factors, especially in shorter meters,are changes in the velocity profile that arecaused by partially blocked strainers or bythe rubber gasket due to the meter connectionbeing too tight 3 .The accuracy of single jet meters reducesdue to wear in the moving parts as theyage. It is especially the starting flow andaccuracy at low flow rates that deteriorate,and thus older meters tend to under-registermore at low flow rates. At higher flow rates,the error can be positive or negative, andmay be exacerbated by sediments or depositsaccumulating inside the meter.31

Chapter 3Table 3-2 Metrological characteristics of common single jet metersClass Size (mm) q start(l/h) q min(l/h) q t(l/h) q p(l/h) q s(l/h)B 15 8 30 120 1500 3000B 20 13 50 200 2500 5000C 15 5 15 22.5 1500 3000C 20 6 25 37.5 2500 5000C 40 22 100 150 10000 20000Note: These are typical values supplied by meter manufacturers, and thus may be better (but notworse) than the requirements of SANS 1529.Types of WaTer MeTersAir moving through the meter will be registeredas water, and thus will cause the meterto over-register. Reverse flow through themeter is registered, but only at about halfthe normal accuracy.3.4.3 Application and InstallationSingle jet meters are mostly used in smalldiameters for domestic and other lowvolume consumers. They are popular fordomestic metering in many countriesdue to their low cost and high reliability.Most single jet meters have to be installedperfectly horizontally and upright to ensureaccurate measurements (especially at lowflows) and a long meter life. However, verticalsingle jet meters are also available.3.5 Multijet Meters3.5.1 MechanismMultijet meters are inferential water meters.Their operation is similar to that of singlejet meters, except that they use a number ofjets to drive the impeller at multiple points.This means that the forces on the impellerare better balanced than in single jet meters,which reduces wear on the moving partsand provides greater durability. A cutawayview of a multijet meter is shown in Figure3-6.3.5.2 CharacteristicsMultijet meters are similar in constructionto single jet meters, although they tend tobe slightly larger in overall size. Multijetmeters are available in both wet and drydial versions. In the dry dial versions of themeter, the watertight compartment housingthe counter and indicator is normallymanufactured from polymer plastic. Inmore expensive meters the compartment isoften made from copper with a temperedglass lens. Examples of multijet meters areshown in Figure 3-7.32

Types of Water MetersFigure 3-6 Cutaway viewof a multijet meter (courtesyof Sensus)Multijet meters are available as cartridgemeters, in which the meter mechanism isenclosed in a pre-calibrated cartridge andcan be replaced without removing the meterhousing from the pipe system.Multijet meters are fitted with strainers onthe inlet side of the meter, which can beremoved for cleaning. A second internalstrainer often covers the openings of themeter chamber. A clogged internal strainercan affect the accuracy of the meter, normallycausing over-registration of the flowto occur.Multijet meters normally use an internalbypass with a regulating screw to adjust theflow passing through the impeller. This allowsthe manufacturer to adjust the meter’serror curve to achieve the best accuracy beforesealing it to prevent meter tampering.On cartridge type meters, the calibrationdevice is internal to the cartridge.The typical metrological characteristics ofcommonly used multijet meters are summarisedin Table 3-3.Types of WaTer MeTersTable 3-3 Metrological characteristics of common multijet metersClass Size (mm) q start(l/h) q min(l/h) q t(l/h) q p(l/h) q s(l/h)B 15 10 30 120 1500 3000B 20 15 50 200 2500 5000B 25 25 70 280 3500 7000B 30 25 100 400 5000 10000B 40 53 200 800 10000 20000B 50 68 450 3000 15000 3000033

Chapter 3Class Size (mm) q start(l/h) q min(l/h) q t(l/h) q p(l/h) q s(l/h)C 15 10 15 1500 3000C 20 12 25 37.5 2500 5000C 25 15 35 52.5 3500 7000C 32 15 40 90 6000 12000C 40 20 100 150 10000 20000C 50 30 75 150 15000 30000Note: These are typical values supplied by meter manufacturers, and thus may be better (but notworse) than the requirements of SANS 1529.Types of WaTer MeTersFigure 3-7 Examples of multijet meters (meters provided by Elster Kent, Sensus and Itron)Reverse flow is possible through multijetmeters, although the measurement error ofthe reverse flow is substantially higher.Multijet meters use reliable and tested meteringtechnology and normally have longworking lives due to the balanced forceson the impeller. They are not very sensitiveto the velocity profile in the pipe and aretolerant towards small suspended solids inthe water. Disadvantages of multijet metersinclude their sensitivity to the installationposition, and that they are often bulkierthan single jet meters. They are not verysensitive to low flow rates, and the startingflow rate can deteriorate significantly withtime. Finally, if some of the jet openings getclogged by dirt, accuracy may be significantlyaffected.34

Types of Water Meters3.5.3 Application and InstallationMultijet meters are mainly used for domesticapplications, and are normally more costeffectivethan single jet meters in dia meterslarger than 20 mm. The accuracy of multijetmeters is not affected much by changes inthe velocity profile. However, they must beinstalled in a horizontal and upright (facingupwards) position for correct operation andoptimal accuracy.3.6 Woltmann Meters3.6.1 MechanismThe Woltmann meter is an inferential meterthat uses an impeller with helical vanes. Itresembles a fan or boat’s propeller. As waterflows over the helical vanes, it causes theimpeller to rotate, and the rotation is thentransmitted to the dial via reduction gearing.Two main types of Woltmann meters areused, called Horizontal (WP) and Vertical(WS) Woltmann meters respectively. HorizontalWoltmann meters have their inletsand outlets directly in line with the pipeline,and the axle of the helical vane is parallel tothe flow. Water flows directly through themeter with little disturbance by the meterbody as shown a section through a HorizontalWoltmann meter in Figure 3-8.Vertical Woltmann meters turn the flow by90º, pass it through the impeller and thenturn it back to the original flow directionas shown in the section through a VerticalWoltmann meter in Figure 3-9.much more common than the vertical version,most of the discussion will focus onHorizontal Woltmann meters.3.6.2 CharacteristicsWoltmann meters are named after the Germanengineer Reinhard Woltmann (diedin 1830), who first used helical vanes tomeasure flow velocities. Woltmann metersare affected by flow distortions or changesin meter dimensions that may interfere withthe way water passes through the meter.Deposits in the meter can cause over-registrationat medium flows and under-registrationat low flows. If deposits are excessive,they may touch the impeller, causing severeunder-registration. All Woltmann metershave dry, sealed dials.Examples of horizontal and vertical Woltmannmeters are shown in Figures 3-10 and3-11 respectively.The easy passage of water through HorizontalWoltmann meters reduces pressureloss through the meter. However, sincethe transducer needs to turn the circularmovement of the impeller through 90º toconnect it to the counter, greater torque isrequired, which reduces the meter’s sensitivityto low flows. The second importantdisadvantage of Woltmann meters is thatthey are sensitive to disturbances in the flowpassing through them. Bends or valves closeto a Horizontal Woltmann meter can affectthe meter’s accuracy. Spiralling flow, whichcan be caused by two successive bends indifferent planes, is especially unfavourablefor their accuracy.Types of WaTer MeTersSince Horizontal Woltmann meters areHorizontal Woltmann meters are used in a35

Chapter 3Types of WaTer MeTersFigure 3-8 Section through a Horizontal (WP)Woltmann meter (courtesy of Itron)large range of pipe sizes, typically between40 and 500 mm. In larger meters, theimpeller will only cover a part of the metercross-section, as illustrated in Figure 3-12.Horizontal Woltmann meters are generallyonly available in Class B, although themetrological characteristics of these metersare often considerably better than the minimumClass B requirements. Manufacturerswill often provide the measured as well asthe legal metrological characteristics of themeter. The typical metrological characteristicsof commonly used Horizontal Woltmannmeters are shown in Table 3-4.Horizontal Woltmann meters can handledifficult working conditions, and a moderateamount of suspended solids in the watercan often be tolerated. The measuring rangeFigure 3-9 Section through a Vertical (WS)Woltmann meter (courtesy of Itron)is very wide and the meter’s working partscan often be replaced without removing themeter body from the pipe system. They canbe installed in virtually any position. Themain disadvantages of Horizontal Woltmannmeters are their sensitivity to disturbancesin the velocity profile, which oftenrequires the need for a minimum length ofstraight pipe upstream and downstream ofthe meter, and their relatively low sensitivityto low flow rates.Vertical Woltmann meters are less susceptibleto disturbances in the flow pattern andmore sensitive to lower flow rates. However,they have larger pressure losses than HorizontalWoltmann meters, and cannot handlethe same maximum flow rates. Finally,they can also be significantly more expensivethan Horizontal Woltmann meters.36

Types of Water MetersTable 3-4 Metrological characteristics of common Horizontal (WP) Woltmann metersClass Size (mm) q start(l/h) q min(l/h) q t(l/h) q p(l/h) q s(l/h)B 50 200 450 3000 15000 30000B 50 200 750 5000 25000 50000B 80 300 1200 8000 40000 80000B 80 300 1800 12000 60000 120000B 100 400 1800 12000 60000 120000B 100 400 3000 20000 100000 200000B 150 1100 4500 30000 150000 300000B 150 1100 7500 50000 250000 500000B 200 1600 7500 50000 250000 500000B 200 1600 12000 80000 400000 800000B 250 3000 12000 80000 400000 800000B 250 3000 18000 120000 600000 1200000B 300 10000 18000 120000 600000 1200000B 300 10000 30000 200000 1000000 2000000B 400 15000 30000 200000 1000000 2000000B 400 15000 45000 300000 1500000 3000000B 500 20000 45000 300000 1500000 3000000B 500 20000 75000 500000 2500000 5000000Note: These are typical values supplied by meter manufacturers, and thus may be better (but notworse) than the requirements of SANS 1529.Types of WaTer MeTers3.6.3 Application and InstallationWoltmann meters are widely used throughoutthe world. They are mainly used tomeasure the consumption of bulk users,or to determine the flow pattern in waterdistribution systems. For large diameterflow meters, manufacturers will express thepermanent flow rate of the meter as themaximum monthly volume that the metermay register without causing a reduction inits service life.Horizontal Woltmann meters can be installedin virtually any orientation withoutaffecting their accuracy. The counter howevershould never be placed upside down.Since Horizontal Woltmann meters arevery sensitive to the velocity profile passingthrough them, it is important to maintain aminimum distance of straight pipe upstreamand downstream of the meter. Thelengths of straight pipe required depend onthe model of meter and the type of disturbances.The manufacturer’s recommendationsshould be followed in this regard. Pipereducers are not normally a problem, aslong as the reduction is done gradually.37

Chapter 3Types of WaTer MeTersFigure 3-10 Examples of horizontal (WP) Woltmann meters. The top left picture shows themeter mechanism without the body. (Meters provided by Sensus and Itron)Normally Horizontal Woltmann metershave larger errors in reverse flow, but certainmodels are designed to have similar accuraciesin both directions. It is important to usesuch a bi-directional model when used inplaces where the flow direction may reverse,for instance in the water distribution network.If this is not done, an effort to use themeter in a water balance will be flawed.Vertical Woltmann meters are very different,and may only be installed horizontallywith the display facing upwards. Since VerticalWoltmann meters are not very sensitiveto disturbances in the flow, significantlyshorter straight lengths of pipes are neededupstream of the meters.38

Types of Water MetersFigure 3-11 Example of a vertical (WS)Woltmann meter (meter provided by Itron)3.7 Combination Meters3.7.1 MechanismCombination meters are not really a separateclass of meter, but rather a combinationof two different classes, in such a way thatthey act as a single meter. The meters thatmake up the combination meter consist ofa large meter, called the bulk or main meter,and a small meter, called the bypass meter.The main meter is typically a multijet orWoltmann meter, and the bypass meter arotary piston, single jet or multijet.An integral part of the combination meteris its control valve, called the changeoveror commutation valve, which is installedin the same line as the main meter. At lowflow rates, the changeover valve closes andFigure 3-12 A large Horizontal Woltmann meter(courtesy of Sensus)all the flow is sent through the bypass meter,which has better accuracy at these lowflow rates. Once the flow rate increases toa certain value, the change-over valve opensand the water flows through the large meteror in some cases through both meters.When the flow reduces to another criticalvalue (lower than the opening value), thechangeover valve automatically closes again.A section through a combination meter,showing the main meter, bypass meter andchangeover valve, is shown in Figure 3-13.3.7.2 CharacteristicsCombination meters have the widest measuringrange of any meter. The meter readermust read both the main and bypass metersand combine the readings to obtain theTypes of WaTer MeTers39

Chapter 3total volume that has passed through thecombination meter. Examples of combinationmeters are shown in Figure 3-14.The changeover valve works automaticallywithout an external energy source. Theflow rate at which it opens is higher thanthe flow rate at which it closes. This ispurposely done to avoid the valve fluctuatingbetween the open and closed positionswhen the flow rate is close to the changeoverpoint.the meters when the switch-over valve isopened and closed.A non-return valve is commonly fitted tothe bypass meter, which means that reverseflow through the meter is impossible. Combinationmeters are manufactured in twobasic configurations. In some cases bothme ters are encased in the same housing, resemblinga single meter. The main benefitof this is saving space. In other cases, thebypass meter is installed on a visibleseparate pipe.Types of WaTer MeTersFigure 3-13 Sectionthrough a combinationmeter (Courtesy ofSensus)The accuracy curve of a combination meteris made up of the accuracy curves of thetwo meters that it consists of, but with acertain area of overlap between the flowrates at which the changeover valve opensand closes. A typical accuracy curve for acombination meter is shown in Figure 3-15.The diamond shaped area in the middleof the curve indicates the overlap betweenCombination meters are not normallycertified metrologically, but each of theindividual meters in the combination hasto comply with the legal metrology requirements.The typical metrological characteristicsof commonly used combination metersare summarised in Table 3-5.Generally combination meters under-registermore as they age. If not maintained, the40

Types of Water Meterschange over valve may start to leak, causingsignificant losses due to under-registrationof these low flows passing through the mainmeter.The main advantage of combinationmeters is their very wide measuring range.Disadvantages are their cost, the fact thatboth meters have to be read to obtain thecombination meter reading, and the needfor maintaining the changeover valve.3.7.3 Application and InstallationCombination meters are normally used forconsumers that have a large range of flows,such as housing complexes, hospitals andFigure 3-14 Examples of combination meters (meters provided by Elster Kent, Sensus and Itron)Lower zoneUpper zoneTypes of WaTer MeTers5%2%Error0%-2%-5%q min q t q nq maxFlow rateFigure 3-15 Typical error curve of a combination meter41

Chapter 3Table 3.5 Metrological characteristics of common combination metersClass Size (mm) Q start(l/h) Q min(l/h) Q t(l/h) Q p(l/h) Q s(l/h)B 50 x 20 10 25 37.5 25 000 50 000B 60 x 20 10 25 37.5 25 000 50 000B 80 x 20 10 25 37.5 60 000 120 000B 100 x 25 13 35 52.5 60 000 120 000B 140 x 40 38 60 2 000 150 000 300 000Note: These are typical values supplied by meter manufacturers, and thus may be better (but notworse) than the requirements of SANS 1529.Types of WaTer MeTersschools. The installation of a combinationmeter has to comply with the requirementsfor both individual meters that make upthe combination meter. It is important toadhere to the manufacturer’s recommendationsin this regard. Most manufacturersrecommend the use of a separate strainer toprotect the meter from suspended solids inthe water.3.8 Electromagnetic Meters3.8.1 MechanismElectromagnetic or magflow water metersuse a principle of electromagnetism, calledFaraday’s Induction Law, to measure thevelocity of the water passing through it.Faraday’s law describes the phenomenonthat if a conductor moves through a magneticfield, an electric voltage is inducedacross the ends of the conductor.In an electromagnetic flow meter, a magneticfield is created across the pipe. Whenwater, which is an electrical conductor,moves through the magnetic field, a voltageis induced that is detected by electrodesin the body of the meter. The voltage isdirectly proportional to the flow velocity,which allows the flow rate to be calculated.The voltage is measured by two electrodesplaced at right angles to the magnetic field.If, for instance, the magnetic field is createdbetween the top and bottom of the pipe,the electrodes will be placed on the sidesof the pipe. Figure 3-16 shows the componentsof an electromagnetic flow meter.Note that the magnetic field is generated bythe coils at the top and bottom of the pipe.The volumetric flow is determined from theflow velocity at the known diameter of themeter.The sensor measurement is transmitted viaan electric signal to an electronic counter,which converts the velocity readings to avolume. The flow rate is normally displayedon an LCD screen, but can also be obtainedas an electronic signal to a telemetry systemor flow logger. In some cases, all the metercomponents are combined in a single meterhousing, while in others, the meter counterand indicator are in a separate location42

Types of Water MetersMeterindicatorFigure 3-16 The mechanismof an electromagnetic flowmeter (adapted fromArregui 3 )Coilsand connected to the sensor via a cable orremote connection.3.8.2 CharacteristicsElectromagnetic meters are very accuratewithin their measuring range (generallyfrom 0.3m/s to 10m/s) and their accuraciesare normally stated as a percentage ofthe reading plus a percentage of the fullscale value. Most electromagnetic metersare configured for a fixed flow velocityrange, typically from 0.5 m/s to 10 m/s.The meter is only able to measure flow inthe defined velocity range, and thus it isimportant to select the correct meter fora given situation. Typical accuracy valuesrange from 0.5% to 0.1%, but decrease atlow flow rates.Electromagnetic meters use electromagnetsto create the magnetic field. Some metersuse direct current (DC) to create a staticElectrodesmagnetic field, while other uses alternatingcurrent (AC) to create a fluctuatingmagnetic field. It is important to knowwhich type of current a meter uses, sinceDC meters typically have to be calibrated atinstallation and at regular intervals afterwardsby setting the zero point when thereis no flow through the meter. However, inAC meters, this is done automatically. Examplesof magnetic flow meters are shownin Figure 3-17.Advantages of electromagnetic meters arethat they offer no obstruction to flow,produce virtually no pressure loss, have nomoving parts subject to wear, are highly accurateand are immune to variations in fluiddensity, pressure, viscosity or temperature.Their accuracy can, however, be affected bydeposits forming on the electrodes, air inthe liquid, turbulence, and to some degree,water hammer (pressure transients). Thesemeters can also be sensitive to damage fromTypes of WaTer MeTers43

Chapter 3lightning strikes. Finally, they also need anelectrical connection or batteries to operate.3.8.3 Application and InstallationThe electrodes of an electromagnetic metershould preferably be mounted on a verticalpipe, but since this is generally not possible,the meter should be mounted with theelectrodes on the horizontal axis to avoidan electrode being situated in an air pocketat the top of the pipe. Some meters havean additional sensor to detect empty pipesituations.On-site power or backup battery power(certain models only) is a necessity and itis possible to lose readings and volumetrictotals if backup power is not available.The general guidelines regarding upstreamTypes of WaTer MeTersFigure 3-17 Examples of magnetic water meters (courtesy of Sensus, Elster Kent and Krohne)44

Types of Water Metersstraight pipe lengths is 5 to 10 times thepipe diameter, with about 3 times the diameteron the downstream side. If possiblethese lengths should be increased, but theloss in accuracy due to obstruction is not asgreat as with some mechanical meters.The meters should be adequately earthedto the pipeline, except where the pipes havecathodic protection, in which case the metermust be isolated from the pipe work bymeans of isolating flanges. Continuity ofthe pipe can be achieved by bypassing themeter with an earthing strap.Doppler ultrasonic flow meters use the socalledDoppler effect, which is the change inthe frequency of a sound wave when it is reflectedback from a moving object. A soundwave created in a moving fluid will hit smalldirt particles or air bubbles moving with thefluid and bounce back towards the origin ofthe signal. The reflected ultrasound wavesare detected by a receiver, and the change inthe wave frequency is measured. This shiftcan then be related to the velocity and thusflow rate of the water. This mechanism isillustrated in Figure 3-19.3.9.2 Characteristics3.9 Ultrasonic Meters3.9.1 MechanismUltrasonic flow meters utilise the propertiesand behaviour of sound waves when passingthrough moving water. Two types of ultrasonicmeters using different mechanisms areused, i.e. transit time and Doppler meters.Transit time ultrasonic flow meters are basedon the phenomenon that sound waves slowdown when moving through the wateragainst the flow, and speed up when theymove with the flow. A transit time ultrasonicmeter has two sound transducersmounted at opposite sides of the pipe at anangle to the flow, as shown in Figure 3-18.Each of these sound transducers will in turnsend out an ultrasound signal to the othertransducer. The differences in the transittimes of the signals are then used to determinethe flow velocity, and subsequentlythe flow rate.The accuracy of transit time ultrasonicmeters depends on the ability of the meterto accurately measure the time taken bythe ultra-sound signal between the soundtransducers. Larger pipes have longer pathlengths and thus the speed of the signal,and the flow rate, can be measured withhigher accuracy. Transit time meters workbetter in clean fluids and thus are ideal fordrinking water pipes. They measure the averagevelocity of a fluid, but are sensitive tothe velocity profile in a pipe. In some casesmulti-beam devices are used to improve themeter accuracy.Permanently installed transit time metersare often called wetted transducer meters,since their sound transducers are in directcontact with the fluid. These meters arevery reliable and typically have relativeerrors between 0.25% and 1%. They canbe used on pipes ranging from 10 mm togreater than 2 m in diameter, although theyare not often used on small diameter waterpipes. The ideal flow velocity range forgood accuracy is 0.5 to 10 m/s.Types of WaTer MeTers45

Chapter 3Figure 3-18 Operatingprinciple of atransit time ultrasonicflow meter (adaptedfrom Arregui 3 )Types of WaTer MeTersFigure 3-19Operating principle ofa Doppler ultrasonicflow meter (adaptedfrom Arregui 3 )46

Types of Water MetersClamp-on transit time meters use soundtransducers that are clamped externally ontothe walls of a pipe to provide portable nonintrusiveflow measurement. They can beused on virtually any pipe material includingmetals, plastics, fibre cement and linedor coated pipes. A disadvantage is that theFigure 3-20Example of anultrasonic flowmeter (courtesy ofSensus)ultrasonic pulses must traverse pipe walland coatings, and thus the thicknesses andacoustic properties of these elements mustbe known. Deposits on the inside pipe surfacecan affect signal strength and performance.Modern clamp-on meters incorporatemicroprocessors that allow mountingpositions and calibration factors to be calculatedfor each application and can provideaccuracies of 0.5% to 2% under controlledlaboratory conditions. In practice, however,various factors decrease the accuracies,including the accuracy of clamping andprecise knowledge of the pipe’s internal wallthickness. Examples of transit time ultrasonicflow meters are shown in Figure 3-20.The advantages of transit time flow metersinclude high accuracy and reliability,making them cost-effective for use in largepipes. The clamp-on version of the meteris easy to install without the need to shutdown the pipe. However, transit time flowmeters are sensitive to distortions in the velocityprofile of a pipe, require an electricitysupply and are not suitable for dirty waters.Doppler ultrasonic water meters can only beused for water that contains particles or airbubbles, and thus they are more suitable fordirty water applications such as raw water.A drawback of Doppler meters is that fluidparticles in the water sometimes moveslower than the water itself, or are concentratedin parts of the pipe with lower velocities(e.g. close to the sides or bottom of thepipe), which can result in a measurementerror of 10% or more. They are also sensitiveto disturbances in the velocity profile,and require an electrical supply. While theyare not suitable as billing meters, they canbe cost-effective as flow monitors if measurementaccuracy is not critical.3.9.3 Application and InstallationUltrasonic meters are often the most costeffective metering option for very largediameter pipes, and thus are not commonlyused for fixed installations in water distributionsystems.Ultrasonic meters are sensitive to disturbancesin the flow, and require significantlengths of straight pipe upstream anddownstream of the meter. The lengths ofstraight pipe required depend on the modelof meter and the source of the disturbance.It is therefore important to adhere to themanufacturer’s installation requirements.The accuracy of transit time ultrasonic meterscan be affected by suspended particlesor air bubbles in the water. In some cases,transit time sound transducers are installedTypes of WaTer MeTers47

Chapter 3Types of WaTer MeTersin the horizontal plane (i.e. on the sides ofthe pipe rather than top and bottom), sinceair bubbles will tend to rise to the top ofthe pipe.Another important factor that may influencethe accuracy of transit time ultrasonicmeters is sediments in the pipe. Sedimentscan accumulate over time at the bottom of apipe, even in clean drinking water networks.The sediments can disturb the ultrasoundsignal, and reduce the pipe diameter, whichwill introduce errors into the measurement.The recommended procedure to avoidsediments accumulating in the meter is toensure that the flow velocity through themeter is between 2 and 6 m/s. At such highvelocities, any sediment will be flushed outof the meter.An advantage of transit-time ultrasonicwater meters is that they can be clamped onthe outside of a pipe. Clamp-on meters areeasy to transport and can be easily installedin any location where the pipe is exposedwithout interrupting the flow. However,the accuracy of clamp-on ultrasonic metersin the field is generally not good and theycannot, for instance, be used to check theaccuracy of in-situ meters. The reasons forthis are that the meter reading is very sensitiveto many parameters that are difficultto determine accurately for a pipe in thefield, including the water temperature, exactproperties of the pipe material (thicknessesand elasticities of the pipe wall and anycoatings and linings used) and condition ofthe inside of the pipe (extent of deposits,sediments and biofilm growth). Due to theirlower accuracy, clamp-on meters are mainlyused to check, or get a rough estimate, ofthe flow in a pipe.For clamp-on meters, it is important thatthe sound transducers make good contactwith the pipe material, and therefore theconnecting points on the pipe should bethoroughly cleaned. In painted pipes, it isrecommended that the paint be removed atthe contact points. For small pipe diameters,the sound transducers of clamp-onmeters are often installed on the same sideof the pipe, with the signal bouncing againstthe opposite pipe wall to reach the receiver.This stretches the travelling distance andtime, and makes the meter more accurate.For large diameter pipes, the sound transducerscan be installed on opposite sidesof the pipe. It is recommended that severalmeasurements are made in different planesof the pipe to ensure reliable readings.Insertion Water MetersAn insertion water meter consists of a probethat is inserted into a pipe to measure theflow velocity at a particular point (or sometimesat a number of points) in the pipe.Depending on the type of insertion meter, itmeasures the velocity using electromagneticprinciples, a turbine or differential pressuremeasurement. Insertion meters are relativelysimple to install (once some basic modificationshave been made to the pipe work) andcan thus easily be moved from site to site.The velocity of water flowing in a pipe is notthe same at all points, and thus it is importantthat the sensor of an insertion meter ispositioned accurately at a representative pointin the flow. Correct use and an undisturbedvelocity profile are critical for accurate measurement,and thus manufacturers’ guidelinesregarding handling, installation and maintenanceshould be strictly adhered to. Insertionmeters are often used to check the accuracyof in-situ flow meters.48

Types of Water Meters3.10 ComparisonThe water meters discussed in this chapterhave large differences in their mechanisms,measuring properties and requirements. Acomparison of the basic properties and requirementsof the different types of metersis summarised in Table 3-6. It is importantto use the actual values for any meter usedin the field. Typical replacement costs formeters are also given in Table 3-7 as a roughguide.Table 3-6 Comparison of the meters discussed in this chapterMeter TypePropertyClassificationSizescommonlyused (mm)Sensitivity tovelocity profileSensitivity towater qualityRotaryPiston(Section3.3)MechanicalVolumetricSingle Jet(Section3.4)MechanicalInferentialMulti Jet(Section3.5)MechanicalInferentialHorizontal(WP) Woltmann(Section3.6)MechanicalInferential15 – 40 15 - 40 15 - 40 40 - 500Combination(Section3.7)MechanicalVaries *50x20-150x40Electromagnetic(Section3.8)ElectromagneticInferential300 - 2000Ultrasonic(Section3.9)UltrasonicInferential400 -4000Insensitive Medium Low High Medium * Medium HighHigh Medium Medium Low Medium * Very Low LowTypical classes B, C and D B and C B and C B BNot categorisedNot categorisedTypes of WaTer MeTersPressure loss High Low Medium Medium High * Very low Very lowOrientationAnyMainlyhorizontalHorizontal Almost any Horizontal Almost anyAlmostanyMinimumstraight lengthupstreamMinimumstraight lengthdownstreamElectricityrequired?None 0 - 5 d None 5 d 5 d 5-10 d 10 dNone 0 - 3 d None 3 d 3 d 3 d 3 dNo No No No No Yes YesNotes: * Varies – the values depend on the individual meter types used; # d is the diameter of the pipe,thus 10 d means a length of pipe equal to 10 times the pipe’s diameter.49

Chapter 3Table 3-7 Typical replacement costs of meters 4Nominal Diameter (mm)Typical replacement cost (R)Types of WaTer MeTers15 R1 700,0020 R1 800,0025 R2 000,0040 R2 200,0050 R3 800,0080 R5 000,00100 R10 000,00150 R16 000,00200 R32 000,00250 R50 000,00300 R100 000,00400 R200 000,00450 R380 000,00Prepaid meters and other meters with electronic displaysConsumers sometimes misunderstand prepaid or other water meters with electronic displays,believing that the electronic display is the meter. It is thus important to communicate to consumersthat the display does not drive the metering process, but simply shows the information itobtains from the water meter, which might be hidden from the consumer’s view. Figure 3-21shows an example of a rotary piston meter with an additional electronic display.Figure 3-21 Rotary piston meter with an additional electronic display50

WaTer MeTerseleCTIon44.1 IntroductionThe aim of this chapter is to provide aguide for selecting appropriate water metersfor different applications in water distributionsystems. It is important to have aconsistent policy on where water metersare installed in the system, and to selectthe most appropriate water meter for eachinstallation.Selecting the right water meter model andsize is very important. It is expensive to purchaseand install a water meter, and thus themeter should perform well for an extendedperiod of time before it has to be serviced orreplaced. Meters that are cheaper may havemuch shorter life spans or higher maintenancerequirements, and thus may not bethe most cost effective option overall.It is not easy to predict the long term performanceof a water meter, as this will differdepending on the meter model, the systemin which it is installed and the water consumptionpatterns of the consumer. Thus itis important that a municipality develops itsown policy on water meter selection basedon its own experience with different metersin its distribution system.A municipality should have its own policy onwater meter selection based on its experiencewith different meters in its distribution system.Larger water meters are more expensivethan smaller meters. In addition, larger metersof the same class have higher starting,minimum and transitional flow rates. Thismeans greater levels of meter under-registration,which translates directly into lowerlevels of income for a municipality. Thus itis important that meters are not over-sized,as is often the case in South Africa andmany other countries 1 .On the other hand, if a water meter is toosmall, the highest flows through the metermay exceed the meter’s design parameters,causing permanent damage to the metermechanism and rapid deterioration inmeter accuracy. As a result, the meter willdevelop high levels of under-registration,and its service life may be substantiallyshortened. To get the greatest benefit from awater meter at the minimum cost, it is criticalthat the meter is correctly sized.Most water meters in a distribution systemare small domestic meters that are quitestandard and not very difficult to select.WaTer MeTer seleCTIon51

Chapter 4It is critical that water meters are correctlysized. A meter that is either too small or toolarge will cost a municipality more over itslifetime.However, correct meters for non-domesticconsumers and bulk domestic consumerssuch as blocks of flats are more difficult todetermine, and can’t be selected withoutanalysis and good judgement.4.2 Meter ApplicationIt is necessary to distinguish between the locationof a meter in the distribution system,and the application and purpose of the meter.The location of meters is important toensure that all consumer usage is metered,but also that water distributed to differentparts of the system is measured to identifyconsumption patterns and leakage.WaTer MeTer seleCTIonIt is necessary to follow a systematic procedureto select the best water meter for agiven application. A meter should never besized simply based on the size of the pipeit will be installed in. Such a selection doesnot consider the actual flow rate variationsthat can be expected to occur, and can thuseasily result in a incorrectly sized meter.A good guide to selecting the right watermeter is to base it on the following questions:• What is the purpose of the meter?• Does the meter comply with the requiredstandards and policies?• Is the meter rated for the expected flowrates and operating conditions?• Which is the most economical meter touse?The first three questions are used toeliminate meters that are not suitable for anapplication, and the last to select the bestmeter out of those that are left. This procedureis discussed in the rest of this chapterand is illustrated in Figure 4-1.Note that most manufacturers are able toprovide software to assist with meter sizing.Appendix B lists some manufacturers thathave meter selection software available.Once it has been determined that a watermeter should be installed at a given location,it is necessary to consider the applicationof the meter. Three major applicationsare identified and discussed: consumer, bulktransfer and management meters.4.2.1 Where Should Meters beInstalled?To get the greatest benefit from a watermetering system, it is important that metersare installed at locations that will supportthe management of the system on technical,financial and management levels.It is generally considered good practice toinstall water meters at the following pointsin a distribution system 2 :• Raw water withdrawals from dams, boreholesor other sources.• Clean water production at the outflow ofwater treatment plants.• Connection points to bulk water suppliersor other municipalities.• Points in the system where it is importantto know how much water is distributed,such as reservoir outflows, pump stationsand off-takes to different areas.52

Water Meter SelectionAvailable metersMeterapplicationSection 4.2ConsumerConnectionsBulkTransferNetworkManagementDomestic General Bulk Bulk supplierDistributionDistrict areaor othermunicipalityLegal and PolicyRequirements?Flow rangeand operationalconditions?Section 4.2Section 4.4WaTer MeTer seleCTIonEconomicconsiderations?Section 4.5Selected MeterFigure 4-1 Steps in the meter selection process53

Chapter 4WaTer MeTer seleCTIon• Supply points to district metered areas(DMAs)• Consumers.Figure 4.2 shows a typical water supplysystem with water meters at recommendedlocations.District Metered Areas (DMAs) are commonlyused to divide a water distributionsystem into smaller units that are easier tomanage. DMAs are isolated from the restof the system, except at one (or sometimesmore) metered connection points. Theytypically consist of around 2 500 serviceconnections 2 .Ideally, all consumers should be metered.Even if the water meter is not used for billingpurposes, it is still important to measurethe supply to a consumer for equity andwater management purposes.In many municipalities, fire hydrants onconsumer properties have not been meteredin the past. This is not recommendedpractice, since consumers can deliberatelyor unwittingly connect their consumptionpipe work to the fire lines, resulting insignificant levels of unmetered consumptionin the system. If fire hydrants are notmetered, it is possible to provide theseconnections with flow detection devices toidentify illegitimate use. Other users thatare often overlooked are public facilitiessuch as parks, swimming pools and publictoilets.Case study: Tshwane generally installswater meters in the followinglocations: 3• Household or small domestic installations:15-25 mm meters.• General consumers such as flats, businesses,hotels, schools, etc: 40-150 mmmeters.• Very large consumers: meters greaterthan 100 mm.• Reservoir inlet and outlet pipes:50-800mm meters.• Zone metering: 50-400 mm meters.• Bulk transfers from bulk suppliers:300-800mm meters.• Own sources such as fountains andsprings, boreholes and treatmentplants: 100-500 mm meters.4.2.2 Consumer MetersConsumer meters measure the water deliveredto different types of consumers, andthus are like cash registers for a municipality.In most cases, these meters’ readings areused to bill consumers for the quantity ofwater consumed, and thus it is importantthat they accurately register the consumption.Strict legislation and standards,including SANS 1529, apply to consumermeters and have to be adhered to. Forinstance, class A meters may not be used asconsumer meters.Even when consumers are not billed forconsumption based on their metered consumption,it is still recommended that allconsumers are supplied with a water meter.This will allow the municipality to identifyconsumers with excessive consumption, for54

Water Meter SelectionReservoirSourceWater treatmentplantPump stationOther municipalityWater towerPumpWaTer MeTer seleCTIonConsumer connection metersBulk transfer metersNetwork management metersFigure 4-2 Typical locations of water meters in a distribution system55

Chapter 4WaTer MeTer seleCTIoninstance due to on-site leakage, and thentake corrective action.Consumer meter connections may beplaced in two categories: small (up to 25mm) and large (> 25 mm) connections.Generally, most meters in a municipalityare domestic meters supplying singlehouseholds. On the other hand, most of thewater consumption is likely to come fromindustrial, commercial and institutionalconsumers, which are often collectivelyreferred to as ICI consumers. Commercialand industrial users typically account for50% of the income from water sales in amunicipality 3 .In most cases a few large consumers areresponsible for a large portion of the consumptionin the system. The water metersinstalled at these consumers are particularlyimportant, since meter inaccuracies mayresult in much greater losses to the municipalitythan for other consumers.4.2.2.1 Small connectionsSmall connections are used for consumersthat require water meters of 25 mm orless, including single housing units and ICI(institutional, commercial and industrial)users with low water consumption. Theconsumption behaviour of domestic users issimilar in nature, and thus it is possible tohave a simplified meter sizing procedure forestimating consumption or even selectingthe meter size. On-site leakage often occurson domestic properties, and thus sensitivityat low flows is important. ICI users inthis category are small and use water mainlyfor human activities such as toilet flushing,washing and cooking.4.2.2.2 Large connectionsLarge connections are those that requiremeters larger than 25 mm. Bulk consumershave the largest consumption in thedistribution system, and thus the sizingand maintenance of their meters are veryimportant.4.2.3 Bulk Transfer MetersBulk transfer meters (sometimes called custodytransfer meters) are used when transferringwater from a source or bulk supplierto a municipality or from one municipalityto another. Payment for the water is basedon the meter readings, and since bulk transfersnormally involve very large quantitiesof water, the accuracy of these meters iscritical. Higher accuracies are often requiredthan for other meters.Bulk transfers are done based on a contractbetween the parties involved that shouldcover metering aspects of the transfer.Bulk suppliers are likely to have a meteringpolicy in place, although municipalitiessometimes install their own meters to verifymeasurements. Electromagnetic and threeor five beam ultrasonic meters are commonlyused in bulk transfers.4.2.4 Management MetersManagement meters measure the distributionof water to different parts of thenetwork. They are essential for many technicaland management functions, includingthe estimation and management of waterlosses, pumping patterns, energy consumption,water demand patterns and hydraulicnetwork calibration. Management meters56

Water Meter Selectionare not used for bulk transfer or consumerbilling, and thus the municipality has morefreedom regarding the type and class ofmeter to use.recognised water meter standard.To get SANS 1529 approval, a meter has topass a number of tests, consisting of:District area meters are management metersthat measure flows entering a districtmetering area (DMA), and are importantfor estimating the demand patterns, futuredemand and leakage of discrete areas of theDMA. Since these estimates are done fordiscrete, relatively small sections of the network,they allow the municipality to betterunderstand demand and leakage trends atdifferent points in the network.Management meters that are not districtarea meters are collectively called distributionmeters.4.3 Legal and PolicyRequirementsAll meters installed in the distributionshould comply with applicable meter legislation.In addition, municipalities shoulddevelop their own policies to standardiseprocesses that suit the conditions in thatmunicipality.4.3.1 Legal RequirementsIn South Africa, national legislation specifiesthat consumer water meters must complywith the requirements of SANS 1529and must be approved in terms of Section18 of the Trade Metrology Act No. 77 of1973 and Regulation Part II. For countrieswhere such a legal framework is absent, itis still crucial for the water supply authorityto only select meters that comply with a• Type approval. A sample of the meteris put through a rigorous series of tests,in cluding external inspection, pressure capacity,pressure loss, brass dezincificationresistance, accuracy, endurance, magneticinterference and several additional tests formeters with electronic components.• Initial verification test, in which meter accuracyis checked at a minimum of threeflow rates.• Verification test, in which each meter istested for accuracy and sealed before it isinstalled in the field.Samples of all consumer water meters soldin South Africa, whether manufactured locallyor fully imported, have to be submittedto the SABS for approval. Once theproduct has been approved, the SABS willissue an approval number for that specificproduct. The approval number is prefixedby the letters SA, e.g. SA123, which mustbe clearly stamped into the body or counterof each meter.Examples of SABS approved meters withtheir approval numbers shown are given inFigure 4-3.Each consumer water meter sold in SouthAfrica must be verified within the bordersof the country for accuracy by a SANAS accreditedtest facility that meets the requirementsof SANS 10378: 2003. The testingofficer must be registered with the Depart-WaTer MeTer seleCTIon57

Chapter 4WaTer MeTer seleCTIonFigure 4-3 Examples of consumer water meters showing their approval numbers (meters provided bySensus)58

Water Meter Selectionment of Trade Metrology as a verificationofficer. Each registered verification officeris issued with a pair of sealing pliers whichbears a unique code. After verifying theaccuracy of a meter, the verification officerseals the meter and marks his/her code onthe seal. The year of verification is addedto the other side of the seal. The verificationofficer’s seal certifies that the meter’saccuracy complies with the requirements ofthe Trade Metrology Act.Imported meters that have been tested overseasmust be re-tested in South Africa asdescribed above, and the seals replaced witha seal with the verification officer’s mark onit as required by the Trade Metrology Act.Figure 4-4 shows examples of seals on watermeters.meters to be replaced at fixed intervals,for instance every five years. Such a policymight have certain quality control advantages,but is very unlikely to be the mostcost-effective solution for a municipality. Itis important that a municipality does notinstall water meters that are designed for afixed replacement period in a system wheremeters are expected to serve for much longerperiods.4.3.2 Policy RequirementsA municipality should develop its ownmeter location and selection policy in linewith its strategic objectives. Various considerationsmay be included in the policy, includingwhere meters should be installed inthe system, what classes of meters should beWaTer MeTer seleCTIonFigure 4-4 Examples of water meter sealsThe dezincification of brass is a problem insome areas of South Africa. In terms of theTrade Metrology Act, all brass water metersshall be manufactured from dezincificationresistant brass (DZR) in compliance withSANS 6509.In some countries, legislation requires waterused and what meter models are acceptable.An example of a meter sizing table that maybe used by a municipality is given in Table4-1. Issues that may be addressed in a meterpolicy include the following:• The meter classes or accuracy required fordifferent applications. It is not sensible to59

Chapter 4WaTer MeTer seleCTIoninstall a meter with an accuracy of 0.25%when an accuracy of, say 5%, is all that isrequired. On the other hand, the measurementof water to consumers shouldbe carried out more accurately to ensureequity and meters with acceptable accuracyshould thus be used 4 .• The types of meters that are suitable fordifferent applications, and preferred orprohibited meter types.• Minimum installation requirements,including fittings, meter boxes to be usedand straight pipe length requirements fordifferent applications.• Logging requirements, including whichmeters should allow for logging, and whatpulse values should be used.A metering policy can guide staff to selectthe right water meter for most generalapplications, only doing more extensiveanalysis and testing where the consumer orcircumstances require it.There are advantages to stick to a few triedand trusted meter models, since is easierand more cost-effective to train meter readersand technicians on fewer models, and italso means that fewer spare parts have to beheld. On the other hand, there should beenough variety in the meter models used toExample: Tshwane’s list of allowable and preferred meter types for different applications.ApplicationTypical metersize range (mm)Household, small consumer 15-25General consumer 40-150Large consumer >150Reservoir outflows 50-800Zone metering 50-400Bulk supplier connections 300-800Own sources 100-500Allowable meter types (preferredmeter type in bold)MultijetRotary pistonWoltmann WPWoltmann WSMultijetRotary pistonWoltmann WPElectromagneticWoltmann WPElectromagneticWoltmann WSInsertion metersWoltmann WPInsertion metersElectromagneticWoltmann WPWoltmann WSElectromagneticWoltmann WPInsertion meters60

Water Meter Selectionensure healthy competition between suppliers.Attention should be given to widerissues, such as logging equipment and communicationinfrastructure. Pre-paid watermeters are known to use different communicationstandards, meaning that they arenot interchangeable and that a municipalityhas to stick to the same supplier whenmaintaining or upgrading meters.Table 4-1: Typical meter sizing table (adapted from Infraguide 2 )MeterSize(mm)TypeFlow range(L/min)Application15 Positive displacement 1-55Single family, duplex, small business (up to10 staff)20 Positive displacement 2-11025 Positive displacement 3-18538 Positive displacement 5-37550 Woltmann WP 7-60050 Combination 1-600Large residences, homes with irrigationsystems or swimming pools, flats with upto 6 units, petrol station without car wash,churches, small institutional users.Residences with pools and irrigationsystem, small to medium apartment buildings(6-17 units), small schools (up to 200students), institutional (up to 50 staff),churches with other activities (e.g. dayschools), large individual commercial buildings,group of commercial buildings (up to10 units).Apartment buildings (18-40 units), old agehomes (up to 50 units), schools (up to 400students), medium-sized hotels (up to 30units), large petrol stations without automaticcar wash, small processing plants,small shopping centres, medium laundromats,restaurants, small hospitals (up to100 beds), medical buildings.Medium apartment buildings (41-120units), duplex complexes (41-80 units),schools with small irrigation systems (up to2000 students), medium hospitals, mediumshopping centres, medium hotels, largepetrol stations with workshops.Schools with irrigation systems (2000-5000students), medium hospitals, communitycentres, nursing homes, city halls.WaTer MeTer seleCTIon61

Chapter 475-100 Woltmann WP 40-1 90075-100 Compound 2-1 600Housing complex or apartment building(over 150 units), large laundromats, largeinstitutional buildings, industrial plants,processing plants, hospital linen services,industrial cleaners.Housing complex or apartment building(120-350 units), large hotel, hospital,high-rise office building, schools (over 2500students), large shopping centres, largegovernment buildings.WaTer MeTer seleCTIon4.4 Flow Range and OperatingConditionsWater meters are expected to operate withinthe legally defined accuracy limits for anextended period of time. Thus it is importantthat a meter should be selected that canhandle the flow rates and operational conditionsexpected at a given installation. Thefirst aspect of an application to consider isthe flow range that the meter is expected tohandle, and the second includes all otheroperational considerations.4.4.1 Flow RangeEach consumer has a certain water demandpattern that a meter will have to cater for.At the higher end of the flow range, it isimportant that the demand should neverexceed the overload flow rate of the meter,and only exceed the permanent flow rate ofthe meter for short periods of time. At thelower end of the flow range, it is importantthat the meter should register low water demandsand on-site leaks to minimise apparentlosses due to meter under-registration.users, the previous water meter readings inthe billing system will provide this information,although these values may have to beadjusted for errors in the readings of the oldmeter. The consumption of similar users inthe same municipality will provide a usefulguide. The average water demand can alsobe estimated based on the type of user,the expected application of water, size andnumber of units served and the number ofpeople or employees.Once the annual average demand is known,the seasonal variation in demand can beestimated. Domestic consumers use significantlymore water in summer than inwinter. This is mainly due to watering ofgardens in summer, although even domesticusers without gardens tend to use morewater in summer than in winter. Non-domesticusers may also have seasonal trendsin their water consumption due to seasonalvariation in production or other waterconsuming activities. In towns that arepopular holiday destinations, consumptionof domestic users and businesses linked tothe tourism industry may be substantiallyhigher during holiday periods.A useful first step is to determine the annualaverage flow rate of the user. For existingWater consumption also varies by day ofthe week. These variations are not normally62

Water Meter Selectionlarge for domestic users, but can be substantialfor commercial or industrial usersthat only operate during weekdays.Finally, water consumption can vary greatlythroughout the day. Domestic consumptiontypically has its peak early in the morningwhen people get up and prepare for the day,and a secondary peak in the early evenings.Commercial and industrial users oftenoperate during specific hours when most oftheir consumption will occur.It is possible to estimate the peak flow ratethrough the meter based on the types andnumbers of fixtures on the property. Loadingunits are associated with different fixturetypes as shown in Table 4-2. Once thetotal number of loading units for a buildinghas been determined, the peak flowrate through the meter can be read off thegraphs in Figure 4-5.Table 4-2 Loading units for different types offixturesFixture TypeLoadingUnitsBath mixer 4.0Toilet with cistern 0.3Toilet with flush valve 16Shower head 0.6Sink mixer 0.6Basin mixer 0.4Bidet mixer 0.2Washing machine 0.6Urinal 0.215 mm tap 0.320 mm tap 1.0Domestic consumers can be grouped accordingto level of income, stand size andnumber of inhabitants for meter sizingpurposes. The peak demand of domesticusers without outdoor consumption rarelygoes above 1 500 l/h 5 , but can be significantlyhigher for users with large stands.For instance, tests on a 300 m 2 house on a2 700 m 2 stand produced a peak demand of2 500 l/h 6 .ICI consumption has much greater variationbetween different users, and thusit is important to consider the specificproperties and needs of a consumer whendetermining their maximum consumption.Below are a number of points that shouldbe considered 2 :• Consider the types and number of waterusing fixtures. A large number of toilets orshowers may mean that many people willuse water simultaneously. Plumbing fittingsmay be designed for water efficiency,and thus use less water than normal fittings.• Industrial processes using water may takewater at a low, constant flow rate or inshort intervals at much higher flow rates.Different processes may use water at differentflow rates, and may be controlledmanually, by timers or by demand.• Landscape irrigation may be controlledmanually or automatically. Automatic systemsmay employ timers or soil moisturelevels to schedule irrigation periods.• Consider the number of building occupantsand hours of operation. Certainin dus tries may have large numbers of staffon site for short periods only, before theydisperse to other work sites.WaTer MeTer seleCTIon63

Chapter 4Example: Determining the peak flow through a meter based on fixture loading unitsConsider a house with 1 bath, 2 showers, 3 toilets, 2 wash basins, 2 sinks, one washing machineand 3 garden taps. First, calculate the total loading units for the house by adding up theloading units for the individual fixtures obtained from Table 4-2:FixtureFixture loadingunits (fromTable 4-2)No of fixturesTotal fixtureloading unitsWaTer MeTer seleCTIonBath mixerShower headsToilet with cisternWash basin mixerSink mixerWashing machine20 mm Garden tap4.00.60.30.40.60.61.012322134.01.20.90.81.20.63.0Total loading units for the house 11.7Now look up the peak flow through the meter from Fig 4-5 (a) as 3100 l/h.• Staff may work in shifts or take breaksat certain times, concentrating water demandinto shorter periods of high usage.• Buildings with flush valve toilets shouldnormally not have water meters smallerthan 25 mm.The lower end of the consumer’s flow rangeis important to estimate, since water metersare least accurate at flow rates lower thantheir transitional and especially minimumflow rates. If significant amounts of waterare consumed at these flow rates, a significantfraction of the consumption may notbe registered by the meter, and thus be adirect financial loss to the municipality.An important source of low flows is leakageon consumers’ properties. In a studyin Johannesburg it was found 7 that around65% of users in medium to high incomeresidential areas had measurable on-siteleakage. Dripping taps use between 0.13and 1.25 litres per hour 8 , while leaks fromtoilet cisterns can range between 0.4 to 14litres per hour 9 . Comparing these flows tothe typical starting flow of 6 l/h of a 15 mmclass C meter, it is clear that such flows willmostly not be registered at all by the meter.Another potential source of low flow ratesoccurs at properties where water is suppliedto a user tank that closes with a ball valve.These ball valves can cause the tank inflowto be small when the tank is close to full.When the tank is full, normal householdconsumption may not lower the water levelenough to open the ball valve fully, andthus a substantial portion of the tank inflowmay occur at low flow rates. Studies incountries where consumer tanks are com-64

Water Meter Selection(a)(b)WaTer MeTer seleCTIonFigure 4-5: Relationship between peak flow and fixture loading units for buildings a) up to 60 loadingunits and b) up to 1000 loading units.monly used have found apparent losses dueto meter under-registration to be around6%, even when the most stringent meterclass D were used 10 . Where class B metersare used, these losses were found to be closeto 20% for new meters, but increase toaround 30% for meters that are 6 to 8 yearsold 11 .There are mechanisms on the market thatclaim to reduce low flow rates through themeter, such as special valves that supply65

Chapter 4WaTer MeTer seleCTIonlow flows through a series of higher flowrate pulses, or special ball valves that donot reduce the flow rate as the tank fills up.However, it is advisable to do a feasibilitystudy to ascertain the effectiveness of thesedevices in the field before they are used on alarge scale.If flow rates are not known, water metersone standard diameter smaller than the supplypipe are often used. However, this is notgood practice since the real consumptionpattern is not necessarily related to the supplypipe size. It should be noted that watermeters are typically one size smaller thantheir end connections.4.4.2 Operating ConditionsBesides the flow range through the meter,it is important that a meter is selected thatsuits the other operating conditions presentat the installation site. While it is often possibleto create installation conditions thatcomply with the meter supplier’s recommendations,this is not always the case. Insuch cases, the appropriate meter shouldbe selected from those that can be installedcorrectly at the site.The most important operational conditionsto consider when selecting a water meter arethe following:• Water quality. The most importantfactor in water quality is solid particles,such as sand or even small pebbles, thatmay be suspended in or moving withthe water. Particles may enter the systemfrom the raw water source if the watertreatment plant is not operating correctly,during repair work on the system, orthrough leak openings when the systemis not pressurised. Rotary piston metersare very sensitive to suspended particles,which might cause them to stop operatingaltogether, and should not be installed insystems that don’t have very good waterquality (class D rotary piston meters areeven more sensitive to suspended particlesthan the class C versions).Single jet and multijet meters can be affectedby suspended particles, althoughnot as much as rotary piston meters, andare thus preferred for domestic meteringin systems with lower water quality.Blocked strainers that alter the flow profilethrough the meter can lead to significanterrors.Woltmann WP meters are tolerant ofbad water quality, and can even be usedfor raw water metering. Electromagneticand travel time ultrasonic meters are notsensitive to suspended particles, as long asthey do not settle in the pipe and thus affectthe pipe diameter. Doppler ultrasonicmeters require some suspended particlesor bubbles to operate, although too manysuspended particles near the pipe wallmay cause wrong readings.• Pressure. Water meters are designed towithstand much higher pressures thanthose in water distribution systems, andthus the system pressure would normallynot be a problem. However, in pumpinglines or bulk pipelines with water hammerproblems, care has to be taken to ensurethat the meter will not be subjected topressures higher than its rating.• Pressure loss. Water will experience66

Water Meter Selectiona pressure loss when passing throughthe meter due to friction and the effortrequired to turn the meter. Strainerscan add significantly to the pressure lossthrough a meter, especially if they areblocked. In most water distribution systems,users are supplied at high pressures(above 20 m), and thus pressure lossesthrough the meter is not a restrictingfactor. However, when the supply pressureis low during certain times of the day,it might be required to use meters withlower pressure losses.• Continuous or intermittent supply.Intermittent supply systems are systemsthat only provide water to consumers atcertain times of the day. It is often a signof a severely lacking supply system, andhas detrimental consequences for waterquality, leakage and the condition of thesystem. Suspended particles in the pipesare unavoidable due to ingress of sandthrough leak openings when the pipe isnot pressurised. When the system is filled,air is pushed through the water meters,causing false readings and potentiallydamaging meters. Finally, reverse flowoften occurs through the meters, creatingfurther metering errors. If intermittentsupply cannot be avoided, it is advisableto stick to simple and robust meter types,such as single jet or multijet meters.• Data logging requirements. There mightbe a specific need for logging the flowthrough a water meter at a certain resolution.In these cases it is important toconsider the pulse values of different metersas a selection criterion. Most metersnowadays can be logged, although not all.It is important to ensure that meters havea reliable interface between the meter andthe logger that will ensure reliable loggerdata. For instance, some meters willbe able to send both forward and reverseflow signals to a logger, while most willtreat all pulses as a sign of forward flow.In some cases meters standing still maydither around a certain value sending falsesignals to the logger.• Theft and vandalism are problems insome areas, requiring special measuressuch as the use of plastic rather than brassmeter bodies. Plastic bodied meters haveto be installed in meter boxes to protectthem from direct sunlight.• Installation requirements. Meters haveto be installed strictly according to theirmanufacturers’ specifications, which mightinclude certain lengths of straight pipe upstreamand downstream of the meter andspecific meter orientations. Smaller metersare normally provided with threaded connections,while larger meters have flangedconnections. Some installation locationsmay not allow for certain installationrequirements, thus limiting the meters thatcan be used at these locations.• Maintenance. Maintenance is veryimportant, especially for large meters,and thus manufacturers’ maintenancerequirements should be considered in theselection process. Meters with lower maintenancerequirements are desirable, butit is important to note that no meter willwork indefinitely without the need formaintenance or replacement• On-site verification. If a need exists toWaTer MeTer seleCTIon67

Chapter 4WaTer MeTer seleCTIonverify the accuracy of meters in situ, provisionneeds to be made for the temporaryinstallation of a verification meter. Theinstallation requirements of the verificationmeter will have to be provided for, aswell as a bypass to allow the meter to beinstalled without interrupting the watersupply.• Electrical supply. Electromagnetic andultrasonic metres normally need mainspower supply. Some meters and relatedequipment operate with battery power(including pre-paid metering systems),and in these cases the working life andreplacement possibilities of the batteriesshould be considered. Other relatedequipment, such as logging or communicationequipment may also require anelectricity supply.• Meter reading. Different meter readingtechnologies are available, and it isimportant that the meter selection shouldconsider the suitability of the meter andits installation position (above or belowground level) for the current and futuremetering technologies that may be usedby the municipality.4.5 Economic ConsiderationsThe final step in the meter selection processdeals with selecting the most cost-effectivemeter from those that have not beenexcluded by the preceding considerations.This means that the financial benefits andcosts of each potential meter are estimatedand used to determine the most appropriatemeter for a given installation.4.5.1 Costs and Financial Benefits ofWater MetersIt is important to realise that the cost of ameter involves much more than just its purchasingprice, but is made up of a numberof components over the lifetime of the meter.The most important cost componentsare as follows:• Price of the meter. The price of a watermeter is a very important factor in meterselection, but should never be the onlyone. For instance, cheaper meters mayhave shorter service lives, or larger apparentlosses than more expensive meters.Thus the other cost considerations shouldbe considered with the meter price. However,when meters are projected to givesimilar performance and other costs, theprice of the meter will obviously be thedeciding factor.• Installation cost. The installation cost ofa meter is linked to its installation requirementsand site conditions. Replacing anexisting meter does not necessarily meanthat the installation costs will be small,since refurbishment and upgrading ofthe installation is often required. In somecases, it is cost-effective to select a replacementmeter with the same length as theold meter so that additional pipe work isavoided.• Service life. The projected service life ofa meter is a very important factor, sinceit determines how often the meter willhave to be replaced. It is often more costeffectiveto use more expensive, but higherquality meters that will have longer servicelives, than cheaper alternatives.68

Water Meter Selection• Cost of meter under-registration over itsservice life. Meter accuracy deteriorates asmeters age, and normally this means thatthe meter will under-register more water.Meter under-registration is a direct financialloss for the municipality since it meansthat not all the water that is delivered to aconsumer is paid for. It is thus necessary toestimate the under-registration losses of ameter over its lifetime based on the errorcurve of a new meter and the projectedreduction in meter accuracy over time.Even though meter under-registrationcosts a municipality, the main motivationfor meter accuracy should be to adhere tothe legal requirements and not the cost ofthe under-registered water.• Water price. The price at which water issold to the consumer is an important parameter,since this is the rate at which lossof income due to meter under-registrationshould be calculated. For municipalitiesthat use block rates, the highest block rateapplicable to the user should be used.• Cost of lost sewage charge. If the municipalsewage charge is based on the waterconsumed, under-registration of the meterwill cause additional financial losses dueto a reduced sewage income.• Maintenance costs. Meters, like any otherworking machinery, require maintenanceto ensure that they work optimally overtheir service lives. Maintenance mayinclude cleaning of strainers, cleaning andrepair of meter boxes, fixing leaks andreplacing damaged register covers. Thespecifications of meter manufacturers andpolicy of the municipality are importantfactors to consider.• Operational costs. In some cases metersuse electricity that will create operationalcosts. If solar energy or backup powerhave to be provided, these factors shouldbe considered as part of the installationcost.• Meter reading costs. Meter reading is acost to a municipality, and using metersthat are easier to read or may be readauto matically, can reduce the meter readingcosts. Future meter reading needsshould also be considered.Manufacturers’ claims of meter performanceare often based on laboratory tests thatmay not be valid under the conditions experiencedin a specific distribution system.Thus it is important that a municipalityshould monitor the performance of differentmeter models in its own system toobtain an accurate picture of actual meterperformance.The main financial benefit of a meterconsists of the revenue generated fromwater that is measured and paid for by theconsumer. However, there are also indirectfinancial benefits derived from a meter,such as lower levels of leakage in the systemdue to better estimations of the levels andlocation of system leaks and the benefitsderived from better system operation andplanning.If the total income generated through ameter is low due to low consumption, freebasic water or lack of payment, it will bedifficult to recover the cost of the meter.However, these meters are still importantfor water management in the system, andthus the financial considerations shouldWaTer MeTer seleCTIon69

Chapter 4aim at selecting the meter that will have thelowest cost over its working life.4.5.2 Methods for Analysing CostefficiencyWaTer MeTer seleCTIonThe difficulty with comparing the costs ofa meter over its service life is that some ofthe expenses occur immediately (e.g. meterprice and installation costs), some annually(e.g. cost of water under-registered)and some at the end of the service life (e.g.meter replacement cost). It is not a simplematter to weigh these costs up against eachother, but various techniques have beendeveloped to do this by taking factors suchas inflation and interest rates into account.The most popular of the techniques are thenet present value and rate of return methods,and it is recommended to investigate thesemethods and apply them when makingbig decisions about bulk meters or meteringpolicy. Some methods for estimatingthe economics of meter replacement arediscussed in Chapter 5.70

5GeTTInG The MosTouT of WaTer MeTers:operaTIon and MaInTenanCe5.1 IntroductionThe number of water meters used by a municipalityoften runs into tens or hundredsof thousands. Ensuring that each of thesemeters is in a good operating conditionand complies with the legal metrologicalrequirements is not an easy task, and callsfor a carefully planned and systematic metermanagement system.An effective meter management systemneeds adequate staff and financial resources.However, the cost of such a system is morethan compensated for by the financial gainsthrough higher efficiencies and lower apparentlosses. It also aids the provision of ahigh level of service to consumers.they either no longer comply with legalrequirements, or it makes economic sense toreplace them. It is always best to prolong theservice life of a meter as much as possible.A database containing information on allmeters in a system forms the core of a goodwater meter management system, as shownin Figure 5-1. This database should beupdated continuously as meters are checkedand handled, and should contain relevantdata on all meters installed in the network.Data that should be handled by the databaseinclude the meter reference number,size, make, date of installation, location,test and repair history. Handling of data onmeters and meter readings are discussed inChapter 6.operaTIon and MaInTenanCeAs with all types of working machinery,water meters have to be actively managed toensure that they provide good service for along period of time. All meters have finiteservice lives and have to be replaced whenFour main components of a managementsystem may be identified, and form theframework for this chapter. These componentsare linked to the central meter managementdatabase, but also to each other.71

Chapter 55.5 5.2operaTIon and MaInTenanCe5.4 5.3Figure 5.1 The water meter management processThe components are:• Installation (Section 5.2) is the first stepin a meter’s service life, and is importantto do correctly. Meters that are notinstalled in accordance with good practiceand manufacturer specifications are boundto have shorter service lives and higherlevels of under-registration.• Maintenance (Section 5.3) is importantto ensure that meters operate efficientlyfor the longest possible time.• Accuracy testing (Section 5.4) need to beMeters don’t last forever and thus have tobe tested at regular intervals and replaced ifnecessary.72

Operation and Maintenancedone on selected meters. Without thesetests it is impossible to know the actualperformance of meters in the system.• Analysis (Section 5.5) of meter accuracyand other data in the meter managementdatabase forms the basis for rationaldecision-making on meter replacement,service and selection.Developing a fully operational meter managementsystem can be a daunting task, andit may not be possible to implement it allat once. In such cases it makes sense to startwith the bulk consumer and bulk transfermeters in the system. While these metersrepresent only a fraction of the meters inthe system, they are normally responsiblefor a large proportion of the income of amunicipality and thus the greatest potentialbenefits will be obtained from them.However, the ultimate goal should alwaysbe to develop a comprehensive managementsystem that includes all water meters in thesystem.5.2 InstallationOnce a meter has been selected (see Chapter4), it has to be installed in the system.Correct installation is critical since it willaffect the performance of the meter for itsfull service life, and possibly also the performanceof future meters when the meter isreplaced. Incorrect installation may lead tohigh under-registration losses and shortenthe service life of a meter.Before the meter is installed, the connectingpipe work must be thoroughly flushed toremove any dirt that may otherwise blockthe meter strainer or damage the meter.Meters can be installed outside the propertyboundary or inside the boundary wherethey are better protected against damageand vandalism. Meters outside the boundaryare easier to access by meter readers, andare thus preferred by many municipalities.Finding and reading meters are made eveneasier if the meter is installed above groundrather than in a meter box, although thisexposes the meter to damage from the elementsand vehicles. In addition, air in thesystem water may collect in meters that aresituated higher than the rest of the pipework and above ground meters should thusbe provided with air valves on the highestpoint upstream of the meter.Metal-bodied meters can be installed in theopen, but plastic meters must be protectedfrom the elements by a meter box. Where ameter box is used, bricks or a small concreteslab must be placed as a foundation underthe meter box and must be levelled toensure that the meter box will also be level.The ground under the meter box must bewell compacted. Sufficient space must beprovided to access the meter for installationand maintenance purposes. A disadvantageof meter boxes is that they can fill withwater due to rain or leakage, which candamage the meter over time and make itdifficult to take readings.Meter installation should only be done bystaff that have been properly trained andhave the right tools to complete the work ina competent manner.A meter installation should comply fullywith the municipalities’ policies and manufacturer’srequirements, including:• Correct direction of flow through theoperaTIon and MaInTenanCe73

Chapter 5Case study: Incorrect meter installations.Look at the multijet meters below and identify the installation problem in each. The correctanswers are given at the bottom of the box.(a)(b)(c)operaTIon and MaInTenanCe(d)(e)(f)Figure 5-2 Examples of incorrect meter installationsAnswers:(a), (b) and (c). Multijet meters installed vertically. Multijet meters are only approved forhorizontal installation. (accuracy affected).(d). Multijet meter face not horizontal (accuracy affected).(e). Multijet meter installed close to rotary piston meter. The pulses generated by the rotarypiston meter will affect the multijet meter’s accuracy. The multijet meter is also installedvertically.(f). Multijet meter face not horizontal (accuracy affected).74

Operation and Maintenancemeter – an arrow on the meter indicatesthe correct flow direction.• Correct orientation of the pipe work (e.g.horizontal or vertical).• Correct orientation of the meter in thepipe (e.g. upright).• Minimum straight lengths of pipe directlyupstream and downstream of the meter.The straight sections of pipe should beinstalled directly to the meter and noreducers, valves or anything else shouldbe installed between the meter and thestraight pipe sections. Where straightpipes sections are not possible, flowstraighteners or a different meter typeshould be considered.• Some meters require the installation of aseparate strainer upstream of the meter.The strainer should be accessible to facilitatecleaning or replacement.• Isolating valves should be installed onboth the upstream and downstream sideof the meter.• Meters using electricity need protectionagainst lightning and electrical surges.Large water meters often have additionalinstallation requirements, such as:• Allowance for in-situ testing of the meter.• Where a meter is installed in plastic pipes,it should be supported by concrete thrustblocks to prevent excessive pipe movementsthat can damage the pipe.• Care should be taken that flange gasketsdo not protrude into the pipe.In cases where fire lines or hydrants arerequired on a property, it is recommendedthat the connection to the fire line is madedownstream of the meter. The fire servicesshould be consulted to ensure that all theirconditions are met.After the installation has been completed,it is recommended that the water is openedgradually to ensure that air is expelledslowly – a meter can suffer damage ifsubjected to high air flows. The followingactions should be taken after each meterinstallation:• The installation must be pressure tested toensure that there are no leaks and that themeter is operating correctly.• Where loggers or electronic flow readingand transmission equipment are used, thedata recorded should be verified againstthe actual meter reading.• As-built drawings should be drawn up.• The meter management database shouldbe updated with the new meter data.5.3 MaintenanceoperaTIon and MaInTenanCe• Flexible couplings to allow the meter tobe easily removed.• Necessary protection from shocks, vibrationsand water hammer.Flow meters are often forgotten when itcomes to routine maintenance. The propermaintenance of any metering device is essentialto ensure it operates at its specifiedaccuracy, and is of even greater importancefor bulk consumer and bulk transfer meters.All meters require maintenance, althoughsome may have lower requirements than75

Chapter 5operaTIon and MaInTenanCeothers. Most meter manufacturers have arecommended maintenance and testingsection in the operation manual for theirmeters.A municipality should develop a watermeter maintenance programme to suittheir particular needs, circumstances andresources. Always keep the potential costof not doing proper maintenance in mind.Maintenance is an ongoing process thatshould be done at a suitable rate to ensurethat backlogs don’t develop. A system thathas a large backlog of required maintenancewill need to invest higher levels of fundsinto maintenance until the required standardis met. Lower levels of expenditure willthen be required to maintain the system atthat level.A problem with a bulk transfer or bulkuser meter has the potential to cause muchgreater losses to the municipality thandomestic and other small meters. Thus itis good practice to concentrate on thesemeters.Water meter maintenance requires simplebut important actions, such as cleaningof strainers, cleaning and repair of meterboxes, fixing leaks and replacing damagedregisters and register covers. In certain cases,The most common problems experienced with water meters in the field1. Suspended solids in the water causing meter mechanisms to get stuck or damaged and meterstrainers to get clogged. These solids enter the system most often due to:a. Large pipe bursts.b. Inadequate flushing of pipes after installations or repairs.c. High velocities in the network stirring up sediments that had collected at the bottom of pipes.d. Inadequate water treatment or malfunctioning treatment plants.2. Service complaints after meter replacement or maintenance caused by:a. Valve on the house connection not re-opened after work.b. Network valve(s) not re-opened after work.c. Installation errors such as a non-return valve fitted the wrong way around.d. On-site leakage occurring, mostly on old and worn internal pipes and fittings.3. Leakage from meter connections.4. Vandalism to meters for scrap metal or in anger, often in ‘retaliation’ when indigent consumersare cut off.5. Damage to meters to due high velocity air flow when drained pipes are refilled.6. Consumer complaints of suspected meter errors.7. Deposit of lime or metal oxides on the inside of meters due to high dissolved solid loads in thewater.8. Meters buried under soil and vegetation.76

Operation and Maintenancemeters have to be removed from site andserviced before being placed back in thesystem. Where possible, large meters shouldbe opened and a careful visual inspectionmade of the meter mechanism for any signsof damage or wear.A checklist should be developed for use bymeter inspectors in the field. This checklistshould include the following information:• Location and date.• Inspector’s name.• Meter identification: make, model, size,serial number and current reading.• Condition of meter installation: meterbody, meter register, pipe work, leakage,upstream valve, downstream valve, meterchamber, strainer, signs of unauthorisedconnections and other.• Actions taken: strainer cleaned/replaced,meter mechanism inspected and/or valveoperation checked.• Action required: cleaning, chamberrepairs, meter test and/or leak repairs.Knowledge of the system will guide a municipalityon maintenance requirements ofdifferent meter models in different supplyareas. The meter management databaseshould be used to identify meters that needurgent inspection or maintenance, andinformation obtained from maintenancevisits should be fed back into the databasefor future use. It is recommended that largewater meters should receive a maintenancevisit at least once a year. Domestic metersrequire less attention and meter readers maybe used to report on leaks or problems thatrequire attention.Meters of 50 mm and larger can often beserviced instead of replaced. However, amunicipality should have the capability tocalibrate and test meters before servicingcan be an option.5.4 Meter TestingLike any mechanical device, water metersdeteriorate with use and generally underregisteras they age. The starting flows andaccuracy at low flows are the areas on theaccuracy curve that tend to deteriorate mostrapidly.It is not possible to predict meter performanceover time for all systems since thereare so many factors that affect the way metersage, including water demand patterns,volume through the meter, water qualityand environmental conditions. Thus eachmunicipality should aim to understand thefactors affecting meter accuracy and theperformance of different meter models inits system.It may also be desirable to log the flowthrough an existing meter in the system tocharacterise the flow pattern through themeter, or determine if the meter is correctlysized. It should be noted that the meterlog ged may have deteriorated significantlyand the results should thus be interpretedin this light.An important step in any meter testing programmeis to ensure that the results of alltests are recorded in the meter managementdatabase for future reference and trackingpurposes. Examining trends in meter accuracyrecords may help identify problemareas and direct the testing programme. ItoperaTIon and MaInTenanCe77

Chapter 5will also help identify when maintenanceis required or when it is time to replace themeter.Any method used to test the accuracy of ameter should be substantially more accuratethan the meter being tested.operaTIon and MaInTenanCe5.4.1 Test MethodsWhen testing meters it is important to takethe purpose of the test into consideration. Ifthe accuracy of a meter needs to be verifiedfor trade purposes, such as in response to aconsumer complaint, the test methods usedhas to comply with metrology legislationand certification. If, on the other hand, thepurpose of the test is to check the meter accuracyas part of a meter replacement study,the municipality can establish their ownprocedures that will satisfy the requirementsfor such a study. It should be emphasisedthat the accuracy of any meter test is veryimportant – if the method used to test metersis not substantially more accurate thanthe meters being tested, the results of thetests are meaningless and cannot be used forany practical application.Various methods are available for testing theaccuracy of water meters. The most precisemethod is to remove the meter from thefield and test it on a laboratory test bench.However, while such measurements arehighly accurate and repeatable, they are notable to replicate site conditions that mightaffect the meter.An alternative is to do field testing and thusobtain the accuracy curve of the meter as itoperates in the field. No testing laboratoriesin South Africa can test meters larger than100 mm, and thus field testing is often theonly method available for large meters.In field tests a calibrated meter is installedIf a water meter needs to be tested for tradepurposes, such as in response to a consumercomplaint, the test method has to complywith metrology legislation and certification.Meters that are tested for other purposes, forinstance as part of a replacement study, canbe tested to the municipality’s own standards.However, the accuracy of these tests are stillvery important.in series with the meter being tested, andwater is passed through both, often viaan outlet such as a hydrant to waste. Itis important that no air is present in thesystem and that the meters are tested underpositive pressure. Thus the flow should becontrolled on the downstream side of bothmeters. A number of field testing methodsare available:• A calibrated master meter is installedin line with the meter being tested. Themeter can be left in place for some timebefore comparing the volumes throughthe two meters. This is an accuratemethod, but requires that allowance forthis have been made in the pipe work.A simple way to test the accuracy ofdomestic meters is to connect the mastermeter to a tap on the property and controlthe flow rate through both meters usingthe tap. It is important to ensure thatother fixtures are not used during the test,and to note that any on-site leakage willnot be measured by the master meter.• An insertion flow meter is installeddirectly upstream or downstream of the78

Operation and Maintenancemeter to be tested. Insertion meters canonly be used on pipes with a special connectionfor inserting the meter. Theaccuracy of the insertion meter shouldbe checked regularly, and previous testsshould have been conducted to determinethe correct position of the meter in thepipe. However, if this is available, installingthe insertion meter is simple.Tests done by Johnson 1 have shown thatinsertion meters are capable of achievinghigh enough accuracies for meter verificationin the field. However, it is importantthat these tests are done in strict accordancewith manufacturer’s specificationsand by a qualified and experienced person.• A portable test rig consists of a bank ofcalibrated flow meters installed on a traileror portable rig. The water passing throughthe meter being tested is diverted throughthe test rig and the flow rates and volumescompared. The test rig is relatively easy toinstall and gives accurate results. Disadvantagesare that the water tested is lost,and that a test rig is expensive to set upand maintain.• A clamp-on ultrasonic meter is installeddirectly upstream or downstream of themeter to be tested. Flow and volumesare compared between the two meters.While clamp-on ultrasonic meters areeasy to install on the outside of a pipe,they are sensitive to the water temperature,pipe wall thickness and condition,and the velocity profile. The errors ofthe ultrasonic meter may well be significantlylarger than those of the meter beingtested, making them unsuitable for meterverification in the field. However, they canbe used to obtain a quick approximationof the flow rate through the meter.To obtain a good estimate of the meter’s errorcurve, it is necessary to test the meter ata number of different flow rates. The moreflow rates are tested, the better the estimateof the error curve, but at least four pointsshould be used. It is important to determinethe starting flow of the meter. Themeter should then be tested at its minimumand transitional flow rates, a point betweenthese two flow rates, and another pointclose to the permanent flow rate. The accuracyof the meter near the permanent flowrate can be assumed to stay constant up tothe maximum flow rate.The relative error of the meter can then beplotted against the flow rate, and a curvefitted through these points as an estimate ofthe meter’s accuracy curve.5.4.2 Large MetersAll large meters need to be tested at regularintervals. The American Water Works Association(AWWA) recommends that metersbetween 25 and 100 mm are tested everyfive years, and meters of 100 mm and largerevery year. Older meters and meters withthe highest readings should be tested first asthey are most likely to have deteriorated.5.4.3 Domestic and Small MetersAWWA recommends that domestic andsmall water meters are tested every 10 years.However, it doesn’t make sense to try to testall domestic and small meters due to thelarge numbers of meters in the system andsmall volumes involved. The recommendedapproach to domestic and small metertesting is to first group the meters by factorssuch as meter model, size, age, volumeoperaTIon and MaInTenanCe79

Chapter 5operaTIon and MaInTenanCemeasured and user type, and then select anumber of meters in each group to test. Itis not recommended to use results from adifferent municipality, since conditions andmeter deterioration may differ significantly.Once meters have been grouped, it is necessaryto test a representative sample of themeters in a group to represent the accuracyof the meters in that group. Sophisticatedstatistical sampling methods are available,but as a general rule of thumb at least 30meters should be tested. (Arregui 2 recommendsa sample of at least 50 users pergroup to test.) More meters tested willresult in a more reliable estimate of themeter accuracies, and thus is recommendedif possible. It is very important that the metersto be tested in each group are selectedrandomly. Thus, to select all the metersfrom a single neighbourhood or street willskew the results and induce errors. A goodway to select (say) 50 meters from a groupis to first number the meters from 1 to N(where N is the number of meters in thegroup). Then use a spreadsheet to generate50 random numbers between 1 an N, andselect these meters for testing.5.5 AnalysisA core part of a meter management programmeconsist of the analysis of meterdata in the meter database in order tounderstand the performance of meters inthe system, and to make certain strategicdecisions and develop action plans.Various types of analyses can be performedbased on the needs of the municipality,such as identifying wrongly sized meters,developing models to predict the performanceof different meter models and determinewhen meters should be replaced.Decisions on meter replacement are probablythe most important to make, since thishas a direct impact on the income generatedfrom water sales. Since meter performancevaried between systems, it is not appropriateto use fixed replacement periods.However, an idea of the expected service lifeof meters can be gained from other areas.Smaller meters can last between 12 and 20years, although service lives of less than 10years have also been reported. Larger meterstypically have lower service lives, with 75mm and larger meters typically lastingbetween 5 and 10 years.These typical periods can be used to obtaina quick estimate of the adequacy of a meterreplacement programme: for instance, if theeconomic life of a meter is 10 years, anda municipality has 80 000 meters in service,it means that 8 000 meters should bereplaced every year to stay up to date withthe programme.Different methods are available for analysingthe financial value of replacing a watermeter. One of these is the payback periodmethod, in which the time required torecover the investment made in income ismeasured.The financial costs and benefits of a watermeter are discussed in Section 4.5.1. Thecost of replacing the meter is made up ofthe meter price and installation cost. The‘income’ generated by making this investmentlies in the increase in income fromthe meter as a result of lower meter underregistration,and the associated increase insewage charges (if linked to water consump-80

Operation and MaintenanceAs an example, if the economic life of a meteris 10 years, 10% of the meters in the systemshould be replaced every year to stay up todate with the replacement programme.tion). Maintenance, operational and meterreading costs can safely be assumed to bethe same for the new and old meter.To calculate the increase in income as aresult of the new water meter, it is necessaryto know the accuracy curve of the meter(through measuring or assuming it), as wellas the distribution of flow rates through themeter. The flow rate distribution should notbe based on measurements from the existingmeter, since these readings will excludeany under-registered water. It may be estimatedfrom similar consumers, or by temporarilyreplacing the existing meter with acalibrated meter. When both the meter errorcurve and flow distribution through themeter are known, it is possible to calculatethe total monthly volume of water underregisteredby the existing meter.The under-registration volume calculationis now repeated for a new meter usingthe manufacturer’s error curve with themeasured flow distribution. The differencebetween the old and new meter errors isthe additional water that will be measuredand billed every month if a new meter isinstalled. The value of the additional watercan now be determined and compared tothe cost of the meter replacement.The analysis of meter economics is complicatedby the fact that certain costs occurat the beginning of the meter’s service life(cost of meter and installation), while othersare distributed over the life of the meter(cost of apparent losses). Since the value ofmoney changes over time due to inflationand interest, it is necessary to use a methodthat incorporates the time value of money.Various methods are available, but only thetwo most common ones are discussed here.They are the Payback Period and Net PresentValue methods.• Payback Period method. In this method,the time required to recover the initialinvestment to purchase and install a meteris calculated from the income generatedby the meter. When the meter replaces anexisting meter, only the additional income(due to the lower apparent losses) is takeninto consideration. Since only a short partof the meter’s life is considered, the timevalue of money doesn’t play a big role andmay be omitted altogether. As a result,the Payback Period method is simple toimplement in addition to its results beingintuitive and easy to understand.• Net Present Value (NPV) method. In thismethod, the income and expenses that willbe made throughout the life of the meterare estimated for the current value of money,i.e. how much will it cost in today’sterms. The method can be used to checkwhether installing or replacing a metermakes economic sense (will the meterbring in more money than it will cost overits lifetime), and compare different metersin an equitable way (for instance, allowinga more expensive meter with better accuracyto be compared to a cheaper meterwith worse accuracy to determine the mostcost-effective meter over the long run).This method is not discussed in detail, butvarious books are available that give a fulldiscussion of this method. In particularoperaTIon and MaInTenanCe81

Chapter 5operaTIon and MaInTenanCethe book by Arregui and the ‘Optimalmeter selection system’ paper by Johnsonlisted in Appendix C are recommended.For domestic meters, users should be placedin groups based on the factors that willinfluence their demand patterns includingtype of service, income, gardening activities,water borne sewage, stand size andtotal water demand. Their consumptionpatterns should be measured with a high accuracymeter, such as a class C or D positivedisplacement meter. For large consumers,a suitable highly accurate meter should beselected – it is especially important that thisA good rule of thumb is that if the incomeor additional income resulting from a meterinstallation should recover the cost of themeter replacement in four years or less, thereplacement represents good value for moneyand should be implemented.Case study: Meter replacements inSão Paulo, Brazil 3About a decade ago, the water companyof São Paulo (SABESP) implemented amassive meter replacement scheme toreduce their apparent losses. They foundthat of the meters that needed to bereplaced, 85% were over-, 4% under-,and only 11% correctly sized. Replacingthese meters made substantial improvementsto their income from meter salesas reflected in the fact that the averagepayback period for replacements wasonly 2 months.meter should be sensitive in the lower flowrange. The test meters should be capable ofbeing logged with the lowest possible pulsevalue – for domestic users a pulse shouldpreferably represent 1 l or less..It is useful to calculate the cost of metersbased on different replacement periodsand to use this as an input into the decisionmaking process. In general terms, thelonger a meter is left in the field before it isreplaced, the cheaper it becomes in capitalexpenses terms. For example, replacingmeters every 10 years will be cheaper thanreplacing the same meters every 5 years,considering only the direct costs of the meterand its installation. On the other hand,the longer a meter is in the field, the moreit will deteriorate and the higher the levelsof apparent losses will be. Thus a 5-yearold meter will have lower levels of underregistrationwhen the meter is 10 yearsExample of a meter replacementanalysisA 200 mm diameter meter is used tomeasure the consumption of a factorythat uses 30 000 m 3 per month. Replacingthe meter at a cost of R20 000 isexpected to improve the meter accuracyfrom -4% to -1% of the total consumption.Calculate the payback period if themeter is replaced for a water price ofR4/kl.The improvement in meter accuracy is3% of the total consumption, or 1 200l/month. Thus the increase in sales fromthe meter will be R4 800 per month,translating to a return period of just 4.2months. This is an excellent investment,since the cost of replacing the meter willbe recovered in less than five months,after which the increased income will bea net ‘profit’ for the municipality.82

Operation and Maintenanceold. When these two costs are added, it ispossible to determine the optimal meterreplacement period, when the total of allthe cost components is at a minimum. Thistype of analysis can be very useful whendone with known accuracy behaviour ofmeters in a particular system.It is recommended that domestic metersare checked and considered considered forreplacement before the age of 10 years, andbulk meters before 5 years.operaTIon and MaInTenanCe83

MeTer readInGand daTaManaGeMenTMeter reading(Section 6.3)Data verification(Section 6.4)Data application(Chapter 76MeTer readInG and daTa ManaGeMenTFigure 6-1 The meter data management process6.1 IntroductionThis chapter deals with the taking and handlingof water meter readings to ensure thataccurate consumption data is gathered. Thedata, in turn, is used for various purposes,such as billing, system management and futureplanning. The selection and implementationof an appropriate data managementsystem for meter data is vital for the success85

Chapter 6MeTer readInG and daTa ManaGeMenTof an integrated water metering strategy. Inmost cases this is done through a specialisedsoftware package.The meter data process involves meter reading,verifying the accuracy of the readingsand making it available various applications.These steps and the links betweenthem are shown graphically in Figure 6-1.Several factors have to be considered whendeciding on a meter reading and billingsystem, such as what department takes responsibilityfor meter reading, whether anypart of the system will be outsourced, andthe type of system that will be used.As water meter readings can be used forseveral purposes, the data may be transferredthrough one or more data managementsystems, each designed for its ownspecific purpose. Consider for examplemonthly readings of water consumption.The first process of capturing and processingwill take place in the meter readingsystem. The data will then be transferred,ideally automatically, to a billing system.The main purpose of the billing systemis to ensure that every consumer is billedfor their month’s consumption. However,meters that are not used for billing purposesshould also be read and handled by the meterreading or meter management databases.Given the correct tools, water supplymanagers can obtain a variety of usefulinformation from the water meter readings,the scope of which goes beyond monthlyconsumption billing. These applications arecovered in Chapter 7.Like the meter management process coveredin Chapter 5, a database sits at the coreof a meter data management system. Thisdatabase, called the meter reading database,may be combined with the meter managementor treasury databases, or it may standon its own with links to them.6.2 Meter Reading DatabaseAlthough the calculations needed to producemeter reading information are theoreticallysimple, the volume of data that isinvolved makes it difficult to use basic softwaresuch as spreadsheets. Even in relativelysmall towns with less than 15 000 stands,it has been found that spreadsheets becomeprohibitively inefficient and clumsy. It istherefore common to use software specificallydesigned for the purpose.The software used must have the functionalityto make the information available tothe user in a seamless structured data tableand it must be possible to sort and querythe data and provide the results of calculatedstatistics in suitably formatted reports.It must also be possible to separately viewthe data and a graphical display of waterconsumption for each user.In many cases meter readings are handledby treasury databases that are geared tofinancial functions and billing. However,treasury databases often do not provide thefunctionality to assist other users of thedata, such as water managers, to make useof it. For this reason it is advisable that treasurydatabases are designed with the needsof other users in mind, or another databaseis linked to the treasury database to makethis data available.Since direct access to treasury or billing86

Meter Reading and Data Managementsystem databases is seldom allowed, the linkto the treasury database is normally done viaa data file of predefined format. This wouldtypically occur through the running of acustom developed routine in treasury system.The data fields that should ideally beincluded in a meter reading database forconsumers and water meters are given inTables 6.1 and 6.2 respectively.Table 6-1 Typical consumer data fields required in a meter reading databaseField Item Comments1 Account number A unique account number.2 Stand IDA unique identification number for the stand, often madeup of the Town, Suburb, Stand, Portion and Sub portion.3 Stand number The registered number of the stand.4 Stand portion Portion a stand is divided into more than one portion.5 Ward Number of the ward the stand is situated in.6 Area CodeA code indicating which area of the town the stand is situated.7 Suburb The name or a code for the suburb the stand is part of.8 GIS Code Location of the stand9 Owner’s name The stand owner’s full name and title.10 Physical address The full street address of the stand.11 Postal address The owner’s postal address.12 Phone numbers Fields for office, work, fax and cell phone numbers.13 Land useA code indicating the registered land use of the property,for instance residential or industrial.14 Zone A code indicating the zoning of the stand.15 Value of land Value of the stand from the valuation roll.16 Value of improvements Value of the stand plus buildings.17 Stand size The area of the stand in standardised units.18 Floor space The total floor space of buildings on the stand.19 Allowable floor space ratioThe ratio of floor space to stand size that is allowed for thisarea.20 Occupied A code indicating whether the stand is occupied or vacant.21 DebtorThe details of the person or body responsible the accounts(if different from the owner). Full name, address and othercontact details should be included.22 Basic tariffThe tariff structure for the basic (fixed) part of the water bill.tariff structure used for the stand.23 Consumption tariff The consumption tariff structure (including block rates).MeTer readInG and daTa ManaGeMenT87

Chapter 6Table 6-2 Typical meter and reading data fields required in a meter reading databaseMeTer readInG and daTa ManaGeMenTField Item Comments1 Meter serial number The serial number on the meter.2 Meter countThe meter number if more than one meter serves the samestand. Typically, the first meter is indicated by 0, the secondmeter by 1, etc.3 Number of units The number housing units served by the meter.4 Installation date Date the meter was installed.5 Number of digitsNumber of digits on the meter dial. Only full m 3 digits areincluded. Typically 4 for small meters and 5 or 6 for largermeters.6 Meter measurement unit Should be m 3 .7 Meter size Meter size in mm.8 Meter route numberThe meter reader route the meter forms part of. Sometimesreferred to as the meter book number.9 Meter location Location of the meter on the stand.10 Average Consumption The average daily demand for the current month.11 Meter reading dataRepeat for a given number of meter readings, for instancethe last 25 readings.11.1 Reading date Date the reading was taken.11.2 Meter reading The reading on the meter.11.3 Reading typeA code describing the type of reading that was done, forinstance for instance a ‘reading’ or ‘estimate’.6.3 Meter Reading6.3.1 Consumer MetersIt is important that water meters are read atregular intervals, preferably once a month.In some cases meters are read less frequentlyand the readings of the intermediatemonths are estimated. This practice savesmoney, but can also introduce significanterrors that may create consumer relationsproblems when sudden large water bills aresent to correct wrong estimates.Different systems are available for consumermeter reading, and a municipality shouldconsider the costs, advantages and disadvantagesof each system to select the mostappropriate one. A combination of technologiesis often the most effective solution.The main meter reading systems availableare:• Direct reading. Meters are read directlyfrom the indicator by a meter reader.Readings can be recorded using pen andpaper, or on a handheld terminal thatallows the readings to be transferred elec-88

Meter Reading and Data ManagementReading water metersWater meters are always read in the same directionas reading a book, i.e. from left to right.By law, all meters have to measure in m 3 (i.e.kilolitres), and must clearly distinguish betweenfull m 3 values and fractions of a m 3 . In somemeters, such as Figure 2-6(a) this is done usingcontrasting colours; typically white numbers ona black background for full m 3 values and whitenumbers on a red background for fractions of am 3 . In other meters, such as Figure 2-6(b), rotatingdisks are used for full m 3 values, and dialsfor fractions of a m 3 . Electronic indicators oftenuse a decimal point or display the fraction valuesin a smaller font. It is common practice for meterreaders to only read the full m 3 values.Unfortunately some large meter models userotating disks to measure tens of cubic meters,and indicate the right-most digit of the full m 3value using a dial. The rotating disk indicators ofthese meters have “x10” written next to them.Such indicators can cause serious reading errors:if only the rotating disks are read and enteredas cubic meters, the reading will be ten timessmaller than the actual consumption, causinglarge losses of income for the municipality.In some cases, this problem is handled by thetronically to the meter reading database.This is preferred, since entering the datamanually creates an additional opportunityfor errors to be introduced.Handheld terminals can also ensure thatall meters on the meter reader’s routeare read, and perform initial verificationof the values entered. Units with builtincamera and GPS systems are nowavailable. They should allow the meterreader to enter problems, such as damagedmeters or meters that are impossibleto access. Direct reading of meters doesmeter database by automatically multiplying thereading by a factor of 10. However, if in suchcases the meter reader enters the full m 3 reading,this will again result in a consumption thatis 10 times greater than the actual consumption.Meters that measure tens of m 3 shouldbe avoided if possible. These meters should beidentified and handled consistently. It is importantthat meter readers are properly trained toidentify and avoid this type of problem.Meter readers should be precise and not sufferfrom any reading impairments. Proper trainingof meter readers is very important. When reading,both the meter serial number and indicatorreading should be taken to ensure the reading isallocated to the correct meter. It is also importantthat meter readers should be trained toidentify and report problems with meters, suchas signs of tampering, damage to meter boxesand leakage.Meter readers should be provided with thecorrect tools, and properly trained on safetymeasures when reading meters. Injury canresult from opening manhole covers withoutthe proper tools and dangerous animals (suchas snakes or bees) may potentially hide insidemeter boxes.not require additional equipment to beinstalled in the meter, but has high labourcosts. Meter readers often have problemsaccessing meters, and reading errors arecommon.• Automatic remote reading. Meter readingsare recorded automatically by connectinga handheld device to a connectionpoint on the meter. The meter reading isautomatically transferred to the device.This allows for a high reading successrate and saves on labour costs since meterreaders can read more meters in a day.MeTer readInG and daTa ManaGeMenT89

Chapter 6Exercise – Meter ReadingTake the readings on the meters below, including both full m 3 values and fractions of a m 3 . Thecorrect answers are given at the bottom of the box.abcMeTer readInG and daTa ManaGeMenTdefAnswers: a) 1604.1672 m 3 , b) 177.179 m 3 , c) 134847.135 m 3 , d) 1073.19645 m 3 , e) 1189.7958 m 3 , f) 0.1465 m 3Figure 6-2 Meter readingsHowever, special and more expensivemeters need to be installed.• AMR (Automatic Meter Reading). AMRuses technology to transmit meter readingsautomatically to a central locationusing phone network or radio frequency(RF) technologies. In telephone AMR systems,meter readings are sent to a centralstation using a fixed or cellular phoneconnection. Telephone readings havea high success rate and saves on labourcosts, since no meter readers are required.The main disadvantages are the costs ofinstalling and maintaining the system.In radio frequency AMR systems the meteris connected to a transponder unit thattransmits the meter reading via a radiofrequency (RF) signal. The transponderis activated automatically by an outside90

Meter Reading and Data ManagementCase study: AMR pilot project in Cape Town 1The City of Cape Town implemented an AMR (Automatic Meter Reading) pilot project to test itsbenefits against those of manual meter reading. The project was implemented in Sunset Beach(an affluent township), the N2 Gateway housing complex (high density complex of two andthree storey apartments) and the Epping industrial area.First, a meter audit was done to identify the meters that were AMR compatible and update themeter database. This was followed by a selective meter replacement programme and the installationof an AMR system.The meter audit proved to be very valuable, and various problems were identified:• Rubble-filled meter chambers.• Poorly constructed meter chambers.• Defective shut-off valves at meters and zone boundaries.• Meters not on the billing database.• Wrong meter sizes and serial numbers in the meter database.• Over-sized water meters, especially in the industrial area.Regarding AMR, it was found that the meter pulse interface unit (PIU) has the greatest influenceon the cost of an AMR system when compared with the cost of the meter. For example, a15 mm domestic meter costs around R180, whilst the PIU could cost anything between R65 andR650 depending on the meter model. For meters larger than 40 mm the difference in cost ofthe meter and PIU was found to be less significant.One of the biggest benefits of AMR proved to be the fact that all meters can be read at thesame time, compared to meters read at different days and times with manual meter readings.This means that the extent and location of water losses in the system can be determined withgreat accuracy by comparing the readings of DMA and consumer readings for exactly the sametime period. Significant losses were found in certain areas of the pilot study, which could thenbe addressed.MeTer readInG and daTa ManaGeMenTtransmitter, which can be carried by ameter reader walking past the property,carried in a vehicle being driven past theproperty, or contained in a fixed areanetwork. The latter option requires theinstallation of infrastructure that will collectthe meter readings and transmit themto a central location via a network ofreceiving and transmitting stations. Thefixed area network fully automates themeter reading process. The system saveson labour costs and has a high readingsuccess rate. However, the cost of installingthe meter units and communicationinfrastructure is high. Units that operateon battery power may require batteriesto be replaced at regular intervals.Inadvanced AMR systems more intelligenceis built into water meters and instructionsmay be sent to the meter from a control91

Chapter 6MeTer readInG and daTa ManaGeMenTstation, is called AMI (Advanced MeteringInfrastructure). The meter may beprogrammed to estimate on-site leakage,record the user’s consumption pattern, orrestrict supply if the user defaults on payments.6.3.2 Bulk MetersThe reading of distribution, bulk transferand even large consumer meters is oftenrequired on a continuous basis to informsystem operators of the current levels offlow and potential problems in the system.This makes direct reading by meter readersunfeasible. The following systems are commonlyused for reading and recording ofbulk meter readings:On-site data logging. A data logger is connectedto the meter and the meter readingsdownloaded from the logger to a computerafter a certain period. The main disadvantageof on-site logging is that the meterreadings are not immediately available, butcan only be accessed after they have beendownloaded. However, data loggers areversatile and can easily be moved to a newlocation to investigate demand or flow patterns.Telemetry data logging. Telemetry systemsuse the same approach as on-site logging,but data is transferred to a central stationthrough a fixed or cellular phone system.The data transfer can be done automaticallyor on demand by a user.Supervisory control and data acquisition(SCADA). SCADA is a common approachto communicate readings from water metersand other system components to a centrallocation. SCADA systems provide automaticand manual control opportunities ofpumps, valves, reservoirs and other equipment.AMR systems as described for consumermeter reading are also suitable for distributionand bulk transfer meters.6.4 Data Verification andProcessingOnce the meter readings have been enteredinto the meter database, it is necessary toverify the data to identify and eliminatepotential errors. Various errors may beincluded in the data, including:• Errors in readings• Errors in dates• Missing readings• Meter replacements and clock-overs• Meter readings not taken on the same dayof the month.The meter reading may also indicate aproblem with the meter itself, such as a meterthat has stopped functioning. It is thusnecessary for the metering database to interpretthe data, identify errors and make correctionswhere possible. It is recommendedthat the water meter reading should be estimatedfor the same day (say the 25 th ) eachmonth. Both the original meter readingsand the estimated monthly consumptionsshould be stored in the system for futurereference. The database can make estimates,handle certain errors automatically and92

Meter Reading and Data Managementraise queries for further investigation by thesystem operators. Some common errors thatshould be identified and handled by a meterreading database are given below:• A stand exists on the system, but no ortoo few water meter readings are availableto estimate its consumption.• Inconsistent dates. The system could notdetermine the order in which the readingstook place due to date inconsistencies.• A meter clock-over that will cause a verylarge water reading one month to be followedby a very small reading the next. Itis important to include information onthe number of digits on the indicator toidentify meter clock-overs.• New or replacement meters that havebeen installed.• Spikes or dips in consumption. Abnormallyhigh or low consumption for astand are often signs of errors in the meterreadings.• Missing readings. Where no readings areavailable for the last month, the systemhas to estimate consumption based on theconsumption history for the stand.MeTer readInG and daTa ManaGeMenT• Long gaps in the meter reading. Whena meter has not been read for a certainnumber of months (typically 3), consumptionestimates become uncertain andan instruction should be given for a readingto be taken.Reporting should be clear and concise withpre-determined standard reports readilyavailable to the user. The functionalityshould also be available for the user to performown queries and produce own reports.93

InTeGraTedWaTer MeTerManaGeMenT:7puTTInG IT all ToGeTher7.1 IntroductionThe aim of this chapter is to provide anintroduction to integrated water metermanagement (IWMM) from a municipality’sperspective. As discussed in Chapter 1,there are four main drivers for a comprehensivewater metering programme: equity,water efficiency, economic benefits andsystem management. These drivers go wellbeyond the aims of specific departments,such as engineering or treasury, but connectwith the broader aims of a municipality’smandate.Various departments of a municipality areaffected by or have an interest in watermeters, but the main departments may beidentified as the treasury, engineering andmanagement. The treasury uses water meterreadings for billing consumers. Engineeringis responsible for installing, maintainingand managing water meters, but alsoneeds water meter data for functions suchas water demand management, non-revenuewater management and network modelling.Management has to ensure that the correctsystems and policies are in place, adequatefunds are allocated to water meter management,and take strategic decisions based onwater meter data.It makes a lot of sense to coordinate andintegrate the management of water metersand water meter data between these departments.This will not only ensure that thegreatest benefits are gained from a watermetering programme in the most cost-effectiveway, but also that policies and decisionsare based on the latest data.To discuss the integrated management ofwater meters in a municipality, the areas affectedby water meters are discussed in fourmain categories:puTTInG IT all ToGeTher95

Chapter 7puTTInG IT all ToGeTher• Strategic planning, covering policies anddecisions on a strategic level, such as themetering strategy, staffing, water tariffsand strategic planning (Section 7.2).• Information management, which dealswith the handling of water meter data,billing and benefits that can be obtainedby integrating consumption data withother systems (Section 7.3).• Asset management, which deals with themanagement of water meters to ensurethat the maximum benefit is obtainedfrom them (Section 7.4).• Water management, which deals withthe way data from water meters can beused to manage water in the most efficientway, addressing issues such as waterdemand and non-revenue water management(Section 7.5).In the final section of the chapter (Section7.6), a questionnaire is provided to allow amunicipality to assess how well it is doingon IWMM, and recommendations aremade regarding the main steps to developan efficient and integrated water metermanagement system.7.2 Strategic PlanningAn effective water meter managementsystem requires strong overall leadership,which has to be driven from a managementlevel to ensure that the systems and effortsof different departments are coordinatedand in line with the larger strategic objectivesof the municipality. A high-level watermetering committee with representationfrom all affected departments should be setup for this purpose.It is important to realise at this level thatwater meters are not the solution to allproblems, but is simply a tool that is usedin the municipal management process. Veryoften problems such as poor payment forservices, vandalism and high on-site leakagerates are the symptoms of deeper socio-economicproblems that have to be addressedby other means, although water meters maywell play an important role.Issues that should be dealt with at a strategiclevel include the following:• Ensuring that sufficient staff memberswith the right qualifications and trainingare appointed to manage the variousaspects of the IWMM process.• Allocation of responsibilities for differentaspects of water metering to differentdepartments. One of the key issues to bedecided is whether engineering or treasuryshould be tasked with meter reading.There is a very strong case for engineeringto take on this role: engineering isresponsible for managing the physicalwater meters, and thus can use meterreaders more efficiently by training themto identify problems with meters thatneed to be addressed while reading themeters.• Development of policies on water meters,including the types of meters to beinstalled, installation standards, procurement,meter management, data handlingand quality assurance.• Development of policies on the handlingof water meter data, including the structureand interconnectedness of databases,what data records to keep, and what type96

Integrated Water Meter Management: Putting It All Togetherof analyses to perform regularly. Outsourcingof certain functions, such asmeter reading, should also be discussed atthis level.• Development of strategies to handleproblems or issues that need to beaddressed (such as the impact of newlegislation, e.g. the new Consumer ProtectionAct) and new technologies (e.g.smart metering and automatic meterreading systems).The conventional metering strategy is to installwater meters on all consumer connectionsand send monthly water bills based onthe actual or projected consumption. Thecost of providing a metered connection tonew consumers is covered by a connectionfee. When water meters are not read everymonth, the consumption for intermediatemonths is estimated based on factorssuch as historic consumption and seasonalpatterns. The consumer is required to pay adeposit to ensure that any unpaid bills arecovered.• Design of water tariff structures, whichdo not only affect municipal income,but can also be used as part of the waterdemand management strategy.• Development of systems for making datamore accessible to different parties.• Budget requirements for water metermanagement.Two of these aspects, metering strategy andtariff setting, are discussed in more detailbelow.7.2.1 Metering StrategyIt is important to realise that differentto consumer metering strategies may beadopted, and that the correct strategydepends on local needs and conditions. Anumber of different metering strategies, ora mix of them, may be used by a municipality,including conventional metering,pre-paid metering, demand restriction andno metering.7.2.1.1 Conventional MeteringA conventional metering system is convenientfor the consumer, since nothing is requiredexcept to pay the bill once it arrives.However, the consumer is expected to paya deposit, and cover the installation costs ofnew meters through a connection fee.Errors in the meter reading process cancause excessive bills and severe inconvenienceto the consumer. A large but hiddenleak occurring on the consumer’s propertycan also be responsible for a very large bill.The major disadvantage of a conventionalmetering system is the effort and cost requiredto manage the system. Meter readershave to be employed to read each meterevery month (or at least every few months).Meter readers often have their own problems,such as getting access to water metersinstalled on consumers’ properties. Thewater meter readings must then be enteredinto a computer system, checked for errors,and bills printed and mailed to consumers.Systems are required to handle errors thatinvariably occur when reading meters ortransferring data. In addition, significantefforts are required to collect outstandingpayments and disconnect users that do notpay their outstanding bills.puTTInG IT all ToGeTher97

Chapter 7puTTInG IT all ToGeTher7.2.1.2 Pre-paid MeteringPrepaid meters are water meters with builtinprocessing units and a mechanism thatcan automatically close a valve to shut off aconsumer’s supply. Consumers purchase waterin advance, and the amount purchasedis transferred through a token or electronicsignal to the meter (see Figure 7-1). Oncethe available credit on the meter has beenused, the prepaid meter automatically shutsdown the supply. In some cases the supplyis shut down completely, while in others asmall flow through the meter is maintained.OIML R49 requires prepaid meters tohave checking facilities, such as protectionagainst reverse flow through the meter.Prepayment water metering provides solutionsto some of the problems associatedwith conventional metering and revenuecollection for both the utility and end-user.It was largely developed in South Africaduring the late 1990s as a solution to lowincomeareas. However, this technology hasgreatly advanced and today it is often usedas an alternative to conventional meteringfor all types of users.To the municipality, the main advantageof prepaid water meters is that revenueis collected in advance, and the supply isautomatically shut down when the availablecredit runs out. This means that meterreadings, an extensive billing system andFigure 7-1 Domestic prepaid water meter (courtesy of Elster Kent)98

Integrated Water Meter Management: Putting It All Togetherdebt collecting systems are not required,reducing the financial risk to the municipalityand saving the cost of an extensive meterreading and data management scheme.The built-in processor and shut-off valvemake prepaid metering systems suitable forother and more advanced functions. Theycan, for instance, be used to automaticallydispense the free basic allowance of waterbefore requiring credit to operate. Alternativelythe meter may revert to a small flowthrough the meter once credit runs out, insteadof shutting down completely. Prepaymentmeters can also be programmed to allowusers to provide some quantity of waterpast the point where the available credit hasbeen depleted with a warning given to theconsumer to recharge the meter credits.Another benefit is that consumers cannotignore their water use, but is constantlyreminded of it by virtue of having to purchasecredit in advance, and when checkingthe credit remaining on the meter. It alsogives consumers control over their ownconsumption and encourages them to managetheir consumption appropriately. Thisoften means that consumers use water moresparingly, thus saving money while helpingto conserve the available water resources.Consumers benefit, since a good creditrecord is not needed in order to get a waterconnection. If a leak occurs on the consumer’sproperty, the loss to the consumeris limited since the meter will automaticallyshut down once the available credit isdepleted.The greatest disadvantage of prepaid watermeters is the increased cost of the meter dueto the additional components, the need forsecure housing with tamper protection andstringent requirements for the meter’s electricalcomponents. Municipal staff workingwith prepaid meters require more skills toinstall, maintain and operate prepaid metersthan conventional meters. Prepaid metersare also more sophisticated and have morecomponents that can fail and cause problems.Thus regular inspection and maintenanceof these meters is more importantthan for conventional meters. Prepaidmeters also need an electrical supply via thenetwork or a battery. A further disadvantageis that consumers might be more inclinedto tamper with or bypass the meter whentheir water is shut off, causing an increasein apparent losses.Experience has shown that careful considerationshould be given to policy around howprepayment systems will be implementedpuTTInG IT all ToGeTherCase study: Prepaid meters in Soweto 1More than 100 000 prepaid water meters have been installed in Soweto. Although the projectmet with organised resistance from the community, including legal action, the matter has beensettled by the Constitutional Court’s ruling that the use of prepayment meters is not unconstitutional.Prepaid meters have been very successful in reducing water demand attributable to wastage:on average for all installed meters, water demand has been reduced from more than 65 klper formal residential property per month to less than 12 kl per property per month (on averagefor the project as a whole), representing a saving of more than 80% in total supply. The costs ofinstalling pre-paid water meters were often recovered within four years.99

Chapter 7puTTInG IT all ToGeTher(or retrofitted) in areas where either a flatrate system or conventional metering systemis in place. A backlash from the communitycan be expected when the system isperceived as being forced onto consumers.It is recommended that meters be installedon demand from individual consumers andthat steps are taken to make the systemmore attractive to consumers.Due to the nature and layout of informalsettlements, prepayment water metersare not considered to be a viable option,whether from a cost recovery, maintenanceor community acceptance point of view.The cost of the prepaid meters in theseareas can often not be recovered since usersgenerally rely on the free basic allowanceand do not purchase enough water throughthe pre-payment meter to recover the costof the meter and installation. The same istrue for very poor areas with poor servicedelivery and intermittent water supply.Factors to consider when selecting a prepaymentwater metering system• Application of the meter and need formetering• Acceptance by political representation andthe beneficiary community• Robustness, performance and reliability• Functionality, especially around tariff structuresand the dispensing of free basic water• Approvals provided by standards settingbodies such as SABS and JASWIC• Cost• Expected service life of the meters• Experience in similar areas• Managerial and technical capacity to operateand maintain the system once installedIn informal communities where water issupplied via communal standpipes, fittinga prepayment meter to the standpipe maybe an attractive option and can significantlyreduce wastage.In middle to high-income areas, the installationof prepayment meters is likely to resultin a drop in overall amounts of revenuecollected. This is because consumers tend tobecome more aware of consumptive habitsand patterns and tend towards more conservativeusage. Thus prepayment meters mayform an important part of a water demandmanagement project.It is very important that a prepaymentwater metering system should be managedwell. Experience has shown that the successand acceptance of these systems are afunction of how well the system is managedafter installation. Dedicated managementand technical staff may be necessary toensure that the system operates efficiently.Attention should be given to the generationof (and attending to) exception reports bythe purchased and installed system. Thisis a distinct advantage of prepayment overconventional systems and meters flagged byway of exception reports should be investigatedfor tampering, vandalism and meterfailure. Given the opportunistic nature ofconsumers (and potentially also officials),neglecting to manage the system well couldquickly corrupt the ideals and objectivessought in the implementation of any largescale project.Because of the potential of vandalism tometers, experience has shown that wheninstalling yard meters, they should preferablybe located on the property and notin the road reserve. This approach obliges100

Integrated Water Meter Management: Putting It All Togetherthe owner to become the custodian of themeter, and in so doing reduces the risk ofvandalism. Enforcement of the custodianprincipal is possible through correctly promulgatedwater supply by-laws.7.2.1.3 Supply restrictionAn effective way to control water consumptionin areas where it is uneconomical toprovide conventional or prepaid meteringsystems, is to restrict the flow to consumers.This gives consumers access to as muchwater as the system will allow them withouthaving to worry about the cost of the water.The consumers get a free or cheap supply,but in return the volumes provided arelimited and thus wastage and leakage arecontrolled. Consumer that can afford toupgrade to a better system may apply andget an upgraded connection, thus allowingthe community to improve their quality oflife as their resources grow. It is also a costeffectivesystem for municipalities, since nometering or billing system is required.Flow restrictors are devices that restrict eitherthe flow rate or volume of water received bya consumer. This category includes tricklefeed systems in which the supply is restrictedto a trickle collected by the user in acontainer such as a roof tank.Electronic flow limiters are devices thatrequire a direct connection with a flowmeter and can dispense a predeterminedvolume of water (typically programmed bythe operator to allow 200 litres per day). Ituses electronics and thus requires a powersupply or battery. The typical battery life ofthese systems is 3 to 5 years. These systemsare more sophisticated than mechanical systems,and also significantly more expensive.7.2.1.4 No metering on unrestrictedconnectionsSystems without flow metering or restrictionsexist in many areas. Users of thesesystems pay for their water through a fixedtariff, or may not pay at all. Since the costto the user is not linked to the water consumption,there is no incentive to use watersparingly, or to fix leaks on their properties.The water consumption and leakage growswith time and the cost of the water supplythrough such a system to the municipalityoften becomes exorbitant. Thus it is importantto ensure that all consumers in thesystem are managed through an appropriatemetering or restriction system.7.2.2 Water Tariff DesignA well functioning IWMM system is usefulin determining a stepped tariff structure forwater sales if the calculated income can bebased on actual water consumption data. Inthis respect it is also important to be able toapply price elasticity to determine the effecton water consumption in the predictionof revenue from water sales with increasedtariffs. This will vary according to land usecategories. Sewer tariffs can also be appliedaccording to the water consumption. Inboth cases the parameter required is the annualaverage daily water demand.The information that is typically availablefrom meter reading, billing or treasury systemsincludes readings for each water meterin the distribution system and is normallystored on a monthly basis along with landuse and other stand related information.(See chapter 6).A general problem is that billing or treasurypuTTInG IT all ToGeTher101

Chapter 7puTTInG IT all ToGeThersystems are not designed to produce themeter information and reports required forthe purposes referred to above. The data isalso often not spatially referenced, whichwould allow links to cadastral database applicationsin GIS. It is therefore necessaryto extract the information from the databasesand use additional manipulation toperform the required statistical calculations.Setting a rate structure to ensure full costrecovery and adequate revenues is essentialfor any universally metered system. In preparinga rate structure, there are two typesof costs to consider: fixed and variable costs.There are also several types of rate structuresavailable:• Fixed rate. Users pay an equal amount foreach unit of water consumed.• Increasing block rate. Users pay an equalamount for each unit of water consumedup to a maximum, at which point a newhigher unit rate is applied for each additionalunit of water consumed. Severalincreasing blocks can be imposed.• Seasonal pricing. In this variation of thefixed rate, users pay an equal amount foreach unit of water consumed; however,the unit rate will vary based on the season.The rate is normally higher in thesummer months to try and curb peakdemands due to dry weather irrigationand recreational use.• Fixed cost plus rate. The user is chargeda minimum amount regardless of consumptionto cover specific fixed costs foroperating the system and then charged arate per unit of water consumed based onone of the structures listed above. Thereare several variations to the rate structureslisted above; however, they are the mostcommon ones used. Each water utilityshould conduct a rate structure study todetermine the most appropriate systemto use.7.3 Information ManagementThe quality and usefulness of an IWMMsystem depends largely on the quality andaccessibility of water meter data and meterreadings. In some cases all data related towater meters are held in the same database,but it is common for different databases tohandle different aspects of the data. This isacceptable, as long as these databases are designedto interact and share information sothat all users have access to the latest data.Municipalities depend on water sales for asignificant part of their income, and thusone of the most important functions ofthe information management system is tocalculate and print accurate water bills.Another very important task of the informationmanagement system is to make awide range of data accessible to users indifferent departments needing it for differentpurposes. While this supports a lot ofthe functions discussed under other headings,the information management systemcan be used for various queries to identifyproblems and obtain a better understandingof the system. A user-friendly query builderis essential. Applications of the informationmanagement system can include thefollowing:• Estimation of water demand distributionfor building accurate hydraulic models ofwater and sewer distribution systems.102

Integrated Water Meter Management: Putting It All Together• Identification of water meters for whichvalues are estimated and not read.• Making consumption data available toconsumers on their water bills or a website.Information on the consumption ofother users in the same category can alsobe given for comparative use.Linking to information to a cadastral shapefile allows spatial representation of the data.Having an aerial photograph and other spatialinformation available (e.g. street names,contours, hydraulic models, topography)further enhances the usefulness of the system.Once again, the underlying databasesshould be accessible so that the informationcan be queried and displayed.7.4 Asset ManagementWater meters are assets belonging to themunicipality and should be managed accordingto good asset management practice.Asset management is in itself an integratedprocess of managing the acquisition, use,management and disposal (replacement) ofassets with the goal of minimising the risksand costs associated with the asset over itslife-cycle. Asset management falls outsidethe scope of this book and thus only a briefoverview of some of the issues addressed byan asset management programme is listed.A downloadable report on asset management,which includes some water meteringcase studies, is given under the RecommendedReading section of Appendix C.puTTInG IT all ToGeTherFigure 7-2 An example of a combined spacial representation of data (courtesy of GLS Consulting)103

Chapter 7puTTInG IT all ToGeTherSome of the aspects of water meters includedunder asset management are:• An asset register (database) that includesall meters in the system and their associateddata.• A meter audit, which entails that metersare found, read, inspected and checkedagainst the meter database.• A meter testing programme to collectinformation on the behaviour of differentmeter models for different consumertypes.• Prioritising meters for replacement toensure the maximum return on investment.• Identifying broken, tampered and inaccuratemeters.• Meter replacement programme.• Monitoring performance of differentmeter models in the system and usingthis information when purchasing newmeters.• Ensuring that meters are correctlyinstalled and maintained.7.5 Water ManagementWater management deals with the movementof water through the municipal systemfrom sources to consumers and otheruses. The application of meters to watermanagement can be divided into threecategories:• The municipal water balance• Water demand management• Non-revenue water management.7.5.1 Municipal Water BalanceThe International Water Association (IWA)has been leading efforts to categorise waterin the municipal system, and does thisthrough the water balance grid shown inFigure 7-3.The IWA water balance divides the systeminput volume into authorised consumptionand water losses. Authorised consumption canbe either billed or unbilled, with the billedportion representing the revenue water.According to the IWA grid, water losses aremade up of real losses (physical leaks fromthe system) and apparent losses. Apparentlosses, in turn, are made up of unauthorisedconsumption (mainly illegal connections)and meter inaccuracies. These meter inaccuraciesrefer to meter under-registrations andmake up a significant fraction of the lossesin the system.A comparison of the readings on bulk transfer,zone, DMA and consumer water meterscan be used to estimate real losses in differentparts of the network. Leak detectionteams and pipe replacement programmescan then be focussed on the most problematicareas.It should be clear that water meters areessential for estimating the size of virtuallyall of the IWA water balance blocks. Thusaccurate water meters are not only criticalfor measuring what happens to water in thesystem, but also for ensuring that apparentlosses are minimised.104

Integrated Water Meter Management: Putting It All TogetherAuthorisedconsumptionBilled authorisedconsumptionUnbilled authorisedconsumptionBilled metered consumptionBilled unmetered consumptionUnbilled metered consumptionUnbilled unmeteredconsumptionRevenueWaterSysteminputvolumeWaterlossesApparent lossesReal lossesFigure 7-3 The water balance grid developed by the International Water Association 2Detailed procedures for estimating the volumeof water in each block, including theroles that water meters play in this process,have been developed and are available fromthe IWA. It is important that the water balancebe estimated correctly using these procedures.In some municipalities the treasuryestimates non-revenue water in their ownway, which may lead to wrong estimatesand a lack of understanding of the problemand how to address it.7.5.2 Water Demand ManagementWater resources are limited, and thus thereis a limit to how much water can be supplied.One of the ways to make water resourcesgo further is to convince consumersUnauthorised consumptionMetering inaccuraciesLeakage on transmission and / ordistribution mainsLeakage and overflows atstorage tanksLeakage on service connectionsup to point of consumermeteringNon-RevenueWaterto use water more efficiently. This process iscalled water demand management.Water meter data can be used in variousways to do water demand management,including the following:• Consumers can be made aware of theirconsumption, how it varies with timeand how it compares to other consumersin the same class. This can be done usinggraphs and tables printed on the municipalwater bills.• Consumption data can be analysed indifferent user categories to determinethe distribution of consumptions in eachcategory, and how the consumptionvaries with stand size and stand value.puTTInG IT all ToGeTher105

Chapter 7The highest consumers in each categorymay be identified and targeted for waterdemand management initiatives.• Consumers can be made aware of onsitelosses and encouraged to have theserepaired.do estimate the water used after each fireevent and these values can be obtained fromthem. Once unbilled authorised consumersare metered, it is possible to evaluate theirconsumption patterns and identify andinvestigate consumers that use excessivequantities of water.puTTInG IT all ToGeTher7.5.3 Non-revenue WaterManagementWater meters can contribute in variousways to estimating and reducing the differentcomponents of non-revenue water.The first component of non-revenue wateris unbilled authorised consumption, whichmay include municipal parks and buildings,as well as water used for fire fighting.Ideally water meters should be installed atall consumption points in the system sothat an accurate assessment of these consumptionscan be made. Fire connectionsare not normally metered, but fire servicesApparent losses consist of two components:unauthorised consumption and meter inaccuracies.Unauthorised consumption may resultfrom illegal connections or from metersthat have been tampered with. One of thebest ways to identify meter tampering (ormeter problems) is to monitor consumptionpatterns and further investigate consumersthat display significant reductions in consumption(see Figure 7-4). In a linked GISdatabase it is possible to highlight propertieswith no water consumption registeredon the meter database as shown in Figure7-5. The stands marked in red in Figure 7-5are clearly occupied and thus should haveconsumption.Figure 7-4 An example of meter readings suddenly stopping, indicating a stuck meter or possibly metertampering (courtesy of GLS Consulting)106

Integrated Water Meter Management: Putting It All TogetherFigure 7-5 A GIS image of an area highlighting stands with no consumption on the metering database(courtesy of GLS Consulting)Meter under-registration losses are controlledby ensuring that meters are replacedwhen they become too inaccurate. Metersaccuracy tends to deteriorate fastest for lowflow rates, which makes on-site losses a particularproblem. These losses are common,and typically run continuously at low flowrates where meters are the least accurate.Convincing consumers to address on-siteleaks will also reduce apparent losses in thesystem.Another way in which apparent lossesmay be reduced is by checking meter sizesagainst measured consumption to identifyand replace meters that are over-sized.7.6 Implementing anIntegrated Water MeterManagement SystemMany municipalities currently have a lackof proper water meter management, andsuffer the consequences through lowerlevels of income from water sales. Oftenthese municipalities also lack experiencedand trained staff to manage such a process.Thus the purpose of this section is to givesome guidance to a municipality regardingwhere they currently stand in terms ofIWMM, and how to go about establishingan IWMM system. To evaluate a municipality’sIWMM system, complete the questionnairein the accompanying text box.puTTInG IT all ToGeTher107

Chapter 7An IWMM strategy takes years to developand implement. However, great improvementscan be made with relatively little effortat the start of the process by focussingon the areas where the greatest benefits willbe gained with least effort. A good rule ofthumb is to start with the source and bulktransfer meters, and the largest consumermeters in the system. In most municipalities,a relatively small number of consumersuse the most water in the system. For instance,more than 50% of the total revenuefrom water sales in the City of Atlanta inthe US comes from less than 3% of theirwater meters 3 .puTTInG IT all ToGeTherThis means that a significant improvementin income can often be made at small costby checking these meters first, and takingsteps to ensure that they operate accurately.Once the larger consumers have been dealtwith, the location where the next highestpotential benefits can be obtained is tacklednext, and so on.It is important to implement strategies thatare written down and subjected to a qualityassurance process so that new staff membersdon’t have to reinvent the wheel. Adequatehuman and financial resources needto be assigned to the project. It is also importantto set measurable objectives for theproject so that progress can be monitoredand management be convinced of the valueof IWMM for the municipality. To assistmunicipalities, a list with recommendedsteps to establish an IWMM programme isprovided in a separate text box.108

Integrated Water Meter Management: Putting It All TogetherQuestionnaire: How does yourmunicipality do on Integrated Water MeterManagement?Tick true answers for the questions below regardingwater meter practices in your municipality.The scores and their evaluation are provided atthe end of the questionnaire.1. Which statements that are true for watersources (bulk supply points, boreholes, damintakes, etc.) and bulk transfers (water sales toand purchases from other municipalities)?a. All points are metered.b. Meters are correctly sized (verified in thelast 5 years).c. Meters have been sized and verified, calibratedand/or replaced in the last 5 years.d. Meter readings are taken continuously.e. (d) is false, but meter readings are taken atweekly intervals or more frequently.2. Which statements are true for bulk consumers(top 10 % or some similar measure)?a. They have been identified for specialattention.b. Meters are correctly sized (verified in the last5 years).c. Meters have been verified, calibrated or replacedin the last 5 years.d. Meter readings are taken at least every month(i.e. no consumption estimates are done).d. All zones are metered.e. Meters have been sized and verified, calibratedand/or replaced in the 5 five years.f. Meter readings are taken at least monthly.4. Which of the following system managementsteps have been taken in the last year (refer toFigure 7-3 as required)?a. Zonal losses estimated using minimum night flowanalysis.b. Revenue water estimated and compared tosystem input volume.c. Unbilled authorised consumptionestimated.d. Apparent losses estimated.e. Real losses estimated.5. Which statements are true for generalconsumer metering (i.e. excluding bulkconsumers)?a. All Industrial, commercial and institutionalconsumers are individually metered.b. All formal residential consumers areindividually metered.c. (b) is false but formal residential consumers notindividually metered are metered in groups offewer than 12 consumers per meter.d. Informal residential consumers are metered ingroups of fewer than 20 consumers or standpipes per meter.puTTInG IT all ToGeTher3. Which statements are true regarding isolatedzones (district metered areas)?a. Zones have no more than 2 500 consumerseach.b. (a) is false, but zones have no more than 6 000consumers each.c. (a) and (b) are false, but some isolated zones arepresent in the system.e. All municipal services for example parks,hospitals, jails, municipal offices and publictoilets are metered.6. Which of the following guidelines or policies doyou have in place?a. Location of meters in the system, including consumerand system management meters.b. Meter sizing and installation standards.109

Chapter 7c. Meter testing and replacement strategy.d. Meter procurement standards.7. Which of the following employees or structuresare in place in such numbers that they can runan efficient metering management system?a. A person in charge of all water meteringmatters.c. Meters are installed at pump stations and majorbranches of bulk pipes.d. Meters in (c) are read at monthly intervals ormore frequently.9. On average, how often are consumer metersread (only tick one answer)?a. Once per month.puTTInG IT all ToGeTherb. Trained and/or experienced staff for meterselection.c. Trained and/or experienced meter techniciansresponsible for installation and replacement.d. Meter readers.8. Which statements are true network managementmeters?a. Meters are installed at all reservoir and tankoutflows.b. Meters in (a) are read at monthly intervals ormore frequently.b. Once every two months.c. Once every three months.10. Is your meter reading data is easily accessibleto and used for the following functions:a. Consumer billing.b. Water loss estimations.c. Water demand management.d. Hydraulic network modelling.e. Long and medium term demandprojections.Calculate your score. Look up the points for each true answer below and add up all your points toobtain your system’s score.1a 1b 1c 1d 1e 2a 2b 2c 2d 3a 3b 3c 3d 3e 3f 4a 4b 4c 4d 4e 5a 5b 5c5 5 5 5 3 4 4 4 4 3 2 1 3 3 3 3 2 2 1 2 2 2 15d 5e 6a 6b 6c 6d 7a 7b 7c 7d 8a 8b 8c 8d 9a 9b 9c 10a 10b 10c 10d 10e1 1 2 2 2 2 2 2 2 2 2 2 1 1 4 2 1 2 2 2 2 2Evaluation80 points and above: Your municipality is doing very well. Keep up the good work!60 to 80 points: A good effort, but you are not getting the most of your metering system. Significanteffort is required to get your metering system up to standard.40 to 60 points: Some things are in place, but major work is required to get your system up tostandard.Below 40 points: Your municipality is not performing well at all, and a substantial effort will berequired to build a proper metering system.110

Integrated Water Meter Management: Putting It All TogetherMain steps in developing an integratedwater meter management system1. Identify all sources of water into your systemand bulk transfers to other municipalities.Ensure that each source or bulk transfer hasa meter that is correctly sized, in good conditionand regularly read (preferably continuously,but at least weekly).2. Identify bulk consumers (top 10 %) in thesystem. Ensure that each bulk consumer hasa meter that is correctly sized, in good conditionand regularly read (at least monthly).3. Identify zones in the distribution system – thesmaller the zones are, the better. Ensure thateach zone has a meter that is correctly sized,in good condition and regularly read (preferablycontinuously, but at least weekly).4. Log the zonal meters to determine theminimum night flow (and thus the leakage)in each zone.5. Estimate current revenue water based onwater sales to consumers.6. Do a preliminary water balance accordingto the IWA grid (Figure 7-3) and identify themost critical areas for intervention. This willtypically lead to a leak detection and repairprogramme focussed on the zones with thehighest leakage rates. A more comprehensivenon-revenue control strategy should bedeveloped from this initial effort.7. Perform an initial review of consumer watermeters in the system using the meter databaseor records and limited, targeted fieldinvestigations. Develop a strategy for theevaluation of consumer water meters, focussinginitially on more affluent areas whereconsumption and payment levels are likely tobe higher. Consumers without meters shouldbe identified and prioritised for meter installation.It is important that all consumers aremetered, although it may be necessary to initiallymeter stand pipes or indigent consumersin groups. A comprehensive meter audit,testing and replacement programme shoulddevelop from this initiative based on a meteringstrategy adopted by the municipality.puTTInG IT all ToGeTher111

lIsT ofreferenCesRChapter 11. Infraguide (2003) Establishing a metering plan to account for water use and loss, Federation ofCanadian Municipalities and National Research Council, 2003,. Downloadable from http://gmf.fcm.ca/files/Infraguide/Potable_Water.2. OECD (2006) Policy brief: improving water management: recent OECD experience. Organisationfor Economic Co-operation and Development, Downloadable from http://www.oecd.org/dataoecd/31/41/36216565.pdf3. Smith, A.L. and Rogers, D.V. (1990) Isle of Wight water metering trial. Journal – Institution ofWater & Environmental Management, 4(5), 403-409.4. Bartoszczuk (2004) Modeling sustainable water prices, Chapter in Handbook of sustainabledevelopment planning: studies in modelling and decision support. M Quaddus and A Siddique(Eds), Edward Elgar PublisherslIsT of referenCesChapter 21. Republic of South Africa, Department of Water Affairs, Water Services Act (as amended).2. Republic of South Africa. Regulations relating to compulsory national standards and measures toconserve water, as published in GN R509 in GG 22355 of 8 June 20013. Republic of South Africa, Trade Metrology Act, No. 77 of 1973 (as amended).4. SANS 1529: Water meters for cold potable water (various parts), South African Bureau ofStandards, Pretoria, (latest edition).5. SANS 10378: General requirements for the competence of verification laboratories in terms of thetrade metrology act, South African Bureau of Standards, Pretoria, (latest edition).6. OIML R 49-1: Water meters intended for the metering of cold potable water and hot water,International Organization of Legal Metrology, Paris (downloadable from www.oiml.org).113

List of References7. ISO 4064: Measurement of water flow in fully charged closed conduits – Meters for cold potablewater and hot water, International Organization for Standardization.8. EN 14154: Water meters, European Committee for Standardization.9. Directive 2004/22/EC of the European Parliament and of the Council of 31 March 2004 onmeasuring instruments, (commonly known as the Measurement Instruments Directive or MID).Chapter 31. Westman, T.F. (1997) Technical report: water meters: a guide to selection, City of Tshwane(unpublished).2. AWWA (1999) Manual M6: Water meters – selection, installation, testing and maintenance,American Water Works Association, Denver CO.3. Arregui, F.J., Cabrera, E., Cobacho, R., García-Serra, J. (2006) Reducing Apparent Losses Causedby Meters Inaccuracies, Water Practice & Technology Volume 1, Number 4.lIsT of referenCes4. eThekwini Water and Sanitation (2010), Asset management plan: small diameter, large diameterand custody transfer check meters, eThekwini (unpublished)Chapter 41. Johnson, E.H. (2001) Optimal water meter selection system, Water SA, v 27, n 4, pp 481-4882. Establishing a metering plan to account for water use and loss by the federation of CanadianMunicipalities and National Research Council, 2003. Downloadable from http://gmf.fcm.ca/files/Infraguide/Potable_Water.3. Westman, T.F. (1997) Technical report: water meters: a guide to selection, City of Tshwane(unpublished).4. Klimko, Ron (1991) Test, repair and calibration of large water meters, Proceedings - AWWAAnnual Conference, Resources, Engineering and Operations for the New Decade, 1991, p 673-6785. Arregui, F., Cabrera, E., Jr., and Cobacho, R. (2006) Integrated water meter management, IWAPublishing, London6. Leonie, T. (2009) Personal Communication (unpublished).7. Van Zyl, J.E., Lobanga, K.P., Lugoma, F.M.T., Ilemobade, A.A. (2008). The state of plumbing inSouth Africa, WRC Project No. K5/1702, Water Research Commission, Pretoria.8. Britton, T., Stewart, R.A., Wiskar, D. (2009) Smart metering as a tool for revealing thecharacteristics of household leakage during a typical reading cycle, Proceedings of the IWA Efficient2009 Conference, Australian Water Association.114

List of References9. Johnson, E. H. (2009). Reliance upon regulations to define water meter accuracy. IWAEfficient2009 Conference, Sydney.10. Rizzo, A. and Cilla, J. (2005) Quantifying meter under-registration caused by ball valves of rooftanks (for direct plumbing systems), Proceedings of Leakage 2005: IWA Specialised Conference,Halifax, Canada.11. Cobacho, R., Arregui, F., Cabrera, E., Cabrera, E., Jr. (2007) Private water storage tanks:evaluating their inefficiencies, Proceedings of Efficient 2007: 4th IWA Specialised Conference onEfficient Use of Urban Water Supply, Jeju Island, KoreaChapter 51. Johnson, E.H. (1999) In situ calibration of large water meters, Water S.A., v 25, n 2, Apr, 1999, p123-1282. Arregui, F., Cabrera, E., Jr., and Cobacho, R. (2006) Integrated water meter management, IWAPublishing, London3. Wilson, D. (2003) Your water meters are your cash registers, The Water Wheel, Jan/Feb, WRC.Chapter 61. De Beer, I. (2010), AMR pilot project, Tender 30S 2007/2008 for the City of Cape Town,Hydrometrix technologies / Cape Digital Solutions (unpublished).Chapter 71. Reference for Soweto Case Study (1); Reference for IWA grid (2)lIsT of referenCes2. Callaway, James L. (1980) Atlanta’s water meter testing program, Proceedings – AWWA AnnualConference, 1980, p 579-583.115

GlossaryAPPENDIXAActual volume (V a). The total volume of water passing through the water meter, irrespectiveof how long this takes.AMR. Automatic Meter Reading.Apparent losses. Water that seems like, but are not really water losses to a municipality. Themain contributors to apparent losses are water meter under-registration, unauthorized consumption(water theft) and accounting errors.Automatic Meter Reading (AMR). AMR uses technology to transmit meter readings automaticallyto a central location using phone network or radio frequency (RF) technologies.Automatic remote reading. Meter readings are recorded automatically by connecting a handhelddevice to a connection point on the meter.GlossaryBulk transfer connection. A connection through which water is transferred between two municipalitiesor from a bulk supplier to a municipality.Calculator. See counter.Check valve. See non-return valve.Classes. See meter classes.Combination meter. A type of meter that consists of two individual meters that operate as asingle unit. A control valve directs flow through one of the two meters or both to provide awide flow range.Consumer connection. A water connection to a consumer. A distinction is made between smalland large connections.Control element. The dial or pointer on the indicator with the smallest value scale, i.e. the dialor pointer that indicates the smallest quantities of water.117

Appendix AConventional meter classes. Meter classes A, B, C and D that has been in common use fordecades. It is gradually being replaced by the new meter classes in many countries.Corrosion. Any chemical reaction through which a material is degraded.Counter. The part of a water meter that keeps track of the volume of water that has passedthrough the meter. It is also called the calculator.Dezincification. Leaching of zinc from brass material through a chemical reaction with thewater passing through the device.Direct meter reading. Meters are read directly from the indicator by a meter reader.Direct transducer. A transducer that uses a direct mechanical link (typically a spindle) betweenthe sensor and counter. Also see magnetic transducer.Distribution meter. A network management meter that is not a district metered area.District area meter. A network management meter used to measure consumption of a districtmetered area.GlossaryDistrict Metered Area (DMA). An isolated area of a distribution system with one or moremetered inputs.DMA. District metered area.Doppler ultrasonic water meter. An ultrasonic meter that estimates the velocity of flow throughthe meter from the change in the frequency of a sound wave when it bounces back from movingparticles in the fluid.Dry dial. The counter and indicator of dry dial meters are contained in a dry, sealed chamber.Also see wet dial.DZR. Dezincification resistant.Electromagnetic meter. An inferential water meter that uses electromagnetic principles tomeasure the average velocity of the water passing through it.Error. The difference between the indicated volume and the actual volume. Thus the error willbe positive for an over-registering meter and negative for an under-registering meter.Error curve. A graphical presentation of the relative error of the meter over its flow range.118

GlossaryFlow meter. See water meter.Flow range. The range of flow rates in which the meter is required to operate within the maximumpermissible error, thus between the minimum and overload flow rates.Flow rate. A volume of water divided by the time taken for this volume to pass a point suchas a flow meter.Helical vane impeller. An impeller with vanes that are shaped in a helical or spiral fashion,similar to the propeller of a motorboat. See figure 2-3.ICI. Industrial, commercial and institutional. Typically used to describe a category of consumers.Impeller. A type of propeller that is rotated by the water moving through the meter. Single jetand multijet meters use radial impellers, while Woltmann meters uses helical vane impellers.See figure 2-3.Indicated volume, V i. The volume of water indicated by the meter. For a perfect meter, thiswill be equal to the actual volume. However, most meters will indicate slightly more or less.Indicator. The part of a water meter that communicates the water meter readings to a meterreader. The indicator can be an analogue or digital device. Examples include dials and electronicdisplays.GlossaryInferential meter. A flow meter with a sensor that measures the velocity of the water passingthrough it, and then converts the velocity into a volume. It is also called a velocity meter.Insertion meter. A water meter that consists of a probe that is inserted through a special connectioninto a pipe to measure the flow velocity at a particular point (or sometimes a numberof points).Intrinsic error. The meter error determined under controlled conditions in a highly accuratetesting laboratory accredited for this purpose.IP68. The symbol used to indicate that the watertighness of a dry dial has been tested to standardIEC 605296. It is important to note how long the dial was subjected to the IP68 test.ISO. International Organization for Standardization.IWA. International Water Association.119

Appendix AIWA water balance. A standard water balance to account for water consumption and losses ina municipal water distribution system. See fig 7-3.IWMM. Integrated water meter management.Large meter connections. Consumer connections with water meters larger than 25 mm.Legal metrology. The branch of metrology that deals with the legal requirements of measurementsand measuring instruments in order to protect consumers and ensure fair trade.Limiting conditions. Extreme conditions, including flow rate, temperature, pressure, humidityand electromagnetic interference, which a water meter is required to withstand withoutdamage or permanent deterioration in its performance.Lower zone. The area of a meter’s error curve between the minimum and transitional flow rates.See Figures 2-8 and 2-9.Magflow meter. See electromagnetic meter.Magnetic meter. See electromagnetic meter.GlossaryMagnetic transducer. A transducer that uses a magnetic link between the sensor and counter.Magnetic transducers are typically used on dry dial meters. Also see direct transducer.Maximum permissible error (MPE). The largest allowable absolute value of the relative error,i.e. the largest allowable relative error when the sign of the error is ignored. The MPE is largerfor the lower flow zone than for the upper flow zone.Mechanical meters. Meters that operate on a mechanical principle, such as moving a pistonor turning an impeller.Meter class. A system that classifies meters according to the accuracy performance. Conventionallya meter has been classified as class A, B, C or D, with class D the most stringent. Inthe new meter classes being introduced in many countries, these classes are replaced with adifferent classification system.Meter error. See error.Metering conditions. The conditions under which a meter operates, such as the flow rate,temperature, pressure, humidity and electromagnetic interference.Metrology. The study measurement accuracy, including how to determine the accuracy of120

Glossarya given measurement device and what sort of accuracy is required when measuring differentthings. Also see legal metrologyMID. The Measurement Instruments Directive that requires water meters in the EuropeanUnion to conform to certain minimum standards.Minimum flow rate, q minor Q 1. The lowest flow rate at which the water meter is required tooperate within the maximum permissible error.MPE. Maximum permissible error.Multijet meter. A flow meter with a radial-vaned impeller rotated by a multiple jets of waterfrom different directions. See figure 3-6.Network management meter. A water meter used to measure the movement of water in thedistribution system. A distinction is made between distribution and district area meters.New meter classes. A new meter class system that has been adopted by a number of countriesthroughout the world, replacing the conventional meter classes.Non-return valve. A valve that only allows flow in one direction through it.OIML. International Organization of Legal Metrology.Overload flow rate, (q sor Q 4). The highest flow rate at which the meter should be able tooperate (within its required accuracy) for a short period without permanent damage to itsaccu racy.GlossaryPermanent flow rate (q por Q 3). The flow rate for which the meter is designed. The metershould be able to operate continuously at this flow rate for its design life without exceeding themaximum permissible error.Positive displacement meter. See volumetric meter.Pressure loss. The pressure difference over the ends of a horizontal meter, at a given flow rate.q min. Minimum flow rate in the conventional meter class system.q p. Permanent flow rate in the conventional meter class system.q s. Overload flow rate in the conventional meter class system.q start. Starting flow rate.121

Appendix Aq t. Transitional flow rate in the conventional meter class system.Q 1. Minimum flow rate in the new meter class system.Q 2. Transitional flow rate in the new meter class system.Q 3. Permanent flow rate in the new meter class system.Q 4. Overload flow rate in the new meter class system.Radial vane impeller. An impeller with straight vanes radiating out from the centre. See figure2-3.Rated operating conditions (ROC). The range of conditions under which the water meter isrequired to operate within its maximum permissible error.Reference conditions. The specified conditions under which the performance of a meter istested in a laboratory.GlossaryRelative error. The error divided by the actual volume. The relative error will be positive for anover-registering meter and negative for an under-registering meter.ROC. Rated operating conditions.Rotary piston meter. A positive displacement meter with a rotating piston.SABS. South African Bureau of Standards.SANAS. South African National Accreditation System.SANS. South African National Standard.SCADA. Supervisory control and data acquisition.Sensor. The part of a water meter that detects the flow passing through the meter, such as a pistonor an impeller. Meters are classified according to the operating principles of their sensors.Single jet meter. A flow meter with a radial-vaned impeller rotated by a single jet of water. Seefigure 3-4.Small meter connections. Consumer connections with water meters of 25 mm or smaller.Starting flow rate or q start: The lowest flow rate at which the meter is able to register a flowpassing through it.122

GlossaryStrainer. A sieve that stops solid particles moving with the water from reaching and damaginga water meter.Supervisory control and data acquisition (SCADA). A system for the transmission of informationand instructions between a central control station and facilities in the field, e.g.reservoirs, pump stations and treatment plants.Transducer. The part of a water meter that transmits the signal detected by the sensor to thecounter of the meter.Transit time ultrasonic water meter. An ultrasonic meter that estimates the average flow velocityfrom the time it takes an ultrasound wave to travel through the fluid.Transitional flow rate, q tor Q 2. A flow rate between the minimum flow rate and permanentflow rate at which the maximum permissible error of the meter changes, dividing the flow raterange into an upper zone and a lower zone.Ultrasonic meter. An inferential water meter that uses the speed of ultrasound waves throughthe water to measure the average velocity of the water passing through it.Upper zone. The part of a meter’s error curve between the transitional and overload flow rates.See Figures 2-8 and 2-9.Velocity meter. See inferential meter.GlossaryVerification officer. A person who is specially qualified and registered with SANAS to verifythe accuracy of water meters.Verification scale interval. The lowest value scale on the control element, i.e. the smallestvolume of water that can be read from the indicator.Volumetric meter. A flow meter with a sensor that measures the volume of water passingthrough it directly by counting off ‘packets’ of water. It is also called a positive displacementmeter.Water meter. A device that measures the volume of water that passes through it. Some documentsdistinguish between ‘water meters’ and ‘flow meters’, but in this document these twoterms are used to refer to a generic water meter.Wet dial. The counter and indicator of wet dial meters are surrounded by a fluid. The fluidcan consist of water from the network or a special liquid in a sealed chamber. Also see dry dial.123

Appendix AWoltmann meter. A flow meter with a helical-vaned impeller rotated by the water moving overit. Horizontal (WP) and vertical (WS) Woltmann meters are available. See figures 3-8 and 3-9respectively.Working pressure. The average pressure that a water meter operates under.WP meter. A horizontal Woltmann meter.WRC. Water Research Commission.WS meter. A Vertical Woltmann meter.Glossary124

orGanIsaTIonsand produCTsAPPENDIXBMetrology Organisations• International Organization of Legal Metrology (OIML), http://www.oiml.org• Bureau International des Poids et Mesures (BIPM), http://www.bipm.org• Intra-Africa Metrology System, http://www.afrimets.org• Southern African Development Community Cooperation in Measurement Traceability (SADC-MET), http://www.sadcmet.org• National Metrology Institute of South Africa (NMISA), http://www.nmisa.orgStandards Organisations• International Organization for Standardization (ISO), http://www.iso.ch/iso/home.htm• European Committee for Standardization (CEN), http://www.cen.eu• American National Standards Institute (ANSI), http://www.ansi.org• African Organization for Standardization (AOS), http://www.arso-oran.org• Southern African Development Community Cooperation in Standardization (SADCSTAN), http://www.sadcstan.co.za• South African Bureau of Standards (SABS), https://www.sabs.co.zaorGanIsaTIons and produCTsOther Organisations• International Water Association (IWA), http://www.iwahq.org• American Water Works Association (AWWA), http://www.awwa.org• African Water Association (AWA), http://www.afwa-hq.org/en• Water Institute of Southern Africa (WISA), http://www.wisa.org.za• South African Water Research Commission (WRC), http://www.wrc.org.za125

Appendix BWater Meter SuppliersThe following companies are the manufacturers or primary suppliers of water meters certified to SABS1529:• Aqua-Loc, www.aqualoc.co.za, ph. (011) 474 1240• Elster Kent, www.elster.com, ph. (011) 470 4900• Itron, www.itron.com, ph. (021) 928 1700• Sensus, www.sensus.com, ph. (011) 466 1680The following companies are suppliers of electromagnetic and ultrasonic water meters• ABB, www.abb.co.za, ph. (021) 506 7700• Krohne, www.krohne.com/South_Africa.1782.0.html, ph. (011)314 1319orGanIsaTIons and produCTs• Siemens, www.siemens.co.za, ph. (021) 935 8000Meter management softwareThe following products specifically deal with aspects of water meter management:• Swift, http://www.gls.co.za/software/products/swift.html, ph.(021) 880 0388• Meterman, www.wms.co.za, ph. 083 377 2635Meter sizing and selection software• Elster Kent• Itron• Sensus126

eCoMMendedreadInGAPPENDIXCWater Meter Management1. Establishing a metering plan to account for water use and loss, by the Federation of Canadian Municipalitiesand National Research Council, 2003, Downloadable from http://gmf.fcm.ca/files/Infraguide/Potable_Water.2. Integrated water meter management, by F. Arregui, E Cabrera Jr., and R. Cobacho, 2006, IWA Publishing,London3. AWWA Manual M6: water meters – selection, installation, testing and maintenance, 1999, AmericanWater Works Association.4. Meter management: best practices for water utilities, by D.L. Schlenger, 1997, Journal of Water Engineeringand Management, March, 33–37.reCoMMended readInG5. Flow measurement handbook, industrial design, operating principles, performance, and applications, byR.C. Baker, 2000, Cambridge University Press, Cambridge.6. A compendium of best practices in asset management, by J.N. Bhagwan, 2009, Global Water ResearchCoalition, Downloadable from http://www.wrc.org.za/ SiteCollectionDocuments/News%20documents/2009-02-23%20GWRC%20final-Jay.pdfWater Meter Selection, Testing and Replacement1. Optimal meter selection system by E.H. Johnson, 2001, published in Water SA Volume 27, No. 4,Downloadable from www.wrc.org.za.2. Evaluating residential meter performance, by P.T. Bowen, J.F. Harp, J.E. Hendricks and M. Shoeleh,1991, American Water Works Association Research Foundation AWWARF. Denver, CO.127

Appendix C3. In-situ calibration of large water meters by E.H. Johnson, 1999, published in Water SA Volume 25,No. 2. Downloadable from www.wrc.org.za.4. Determining the economical optimum life of residential water meters, by H. Allender, 1996, Journal ofWater Engineering and Management, September; 20-24.5. Implementing a large-meter replacement program, by M.J. van der Linden, 1998, published in JournalAWWA, August, pp 50-56.6. Economic analysis for replacing residential meters, M.D. Yee, 1999, published in Journal AWWA, July,pp 72-77.7. Domestic water meters: influence of various fittings and installation configurations on accuracy of15 mm water meters, by P. Chipindu and C.J. Wantenaar, Water Research Commission ReportNo.948/1/00, Downloadable from www.wrc.org.za.reCoMMended readInGWater Billing and Accounts1. Guidelines on domestic water accounts – towards a consistent approach in South Africa, by S. Slabbert,2010, WRC Report no TT 457/10, Downloadable from www.wrc.org.za.2. Towards standards for municipal invoices in South Africa, by S. Slabbert, 2010, WRC Report noTT 458/10, Downloadable from www.wrc.org.za.Water Meter Standards1. SANS 1529-1: Water meters for cold potable water Part 1: Metrological characteristics of mechanicalwater meters of nominal bore not exceeding 100 mm, South African Bureau of Standards, Pretoria2. SANS 1529-4: Water meters for cold potable water Part 4: Mechanical meters of nominal bore exceeding100 mm but not exceeding 800 mm, South African Bureau of Standards, Pretoria3. OIML R 49-1, Water meters intended for the metering of cold potable water and hot water. Part 1: Metrologicaland technical requirements, International Organization of Legal Metrology, Paris. Downloadablefrom www.oiml.org.128

INTRODUCTION TOINTEGRATED WATERMETER MANAGEMENTEDITION 1About the authorDr JE (Kobus) van Zyl holds Bachelor and Master’s degrees in Civil Engineering, and aDiploma in Scientific Computing from the Rand Afrikaans University (now University ofJohannesburg). He obtained a PhD in Civil Engineering at the University of Exeter in 2001.He is a registered Professional Engineer, a member of the South African Society of CivilEngineering, American Society of Civil Engineers and the International Water Association,and a Fellow of the Water Institute of Southern Africa. He was Chair of the Department ofCivil Engineering Science at the University of Johannesburg (2005-2007), and held theRand Water Chair in Water Utilisation at the same institution. In 2008 Dr van Zyl chairedthe 10 th Water Distribution System Analysis (WDSA) Conference, held in the Kruger NationalPark. This is one of the two leading international conference series on water distributionsystems, and the first WDSA conference held outside the USA.He has twice been awarded the Best Paper prize in the Journal of the South African Societyfor Civil Engineering, and is an Associate Editor of the Journal of Water Resources Planningand Management.Dr van Zyl’s research focuses on water distribution systems, and his current interests includehydraulic modelling, stochastic analysis, water losses, metering, and water demand management.Dr Van Zyl currently holds an associate professorship at the Civil Engineering Departmentof the University of Cape Town.