Roof-Top Rainwater Harvesting Best Practices Guide - International ...

Roof-Top Rainwater 

Harvesting Best 

Practices Guide

ACKNOWLEDGEMENTS 

International Relief and Development (IRD) would 

like to thank USAID’s Office of US Foreign Disaster 

Assistance (OFDA) for their on-going partnership 

and shared commitment to improving the health 

and livelihoods of vulnerable communities in 

Zimbabwe and across the globe. Many thanks also 

go to everyone on the IRD team who contributed 

to the creation of this best practices guide. Lastly, 

a special thank you is extended to participants 

of the Regional Rooftop Rainwater Harvesting 

Workshop for Southern Africa held in Harare 

from 5-6 December 2012 whose contributions 

and feedback enabled us to develop this best 

practices guide.

Roof-Top Rainwater Harvesting 

Best Practices Guide 

1. INTRODUCTION ................................................. 1 

1.1. Best Practices Guide ........................................ 2 

2. BACKGROUND................................................... 4 

2.1. Overview .................................................. 4 

2.2. Rainwater Harvesting Technologies ......................... 4 

3. HARDWARE: DESIGN OPTIONS AND MATERIALS .................. 5 

3.1. Design Considerations...................................... 5 

3.2. Infrastructure .............................................. 5 

3.3. Design Tools ............................................... 5 

3.4. Design Best Practices ....................................... 7 

3.5. Cost of Technology: ....................................... 11 

4. SOFTWARE: COMMUNITY OWNERSHIP .........................13 

4.1. Beneficiary Selection ......................................13 

4.2. User Contributions ........................................15 

4.3. Collaboration with Government, Local Authorities 

and Partners ..............................................15 

4.4. Gender Considerations ....................................16 

4.5. System Management and Training .........................18 

4.6. Monitoring and Evaluating ................................19 

5. REPLICABILITY FACTORS ........................................21 

6. REFERENCES....................................................22

Tables 

Table 1: Roof-top Rainwater Harvesting Water Storage Methods ............... 3 

Table 2: Materials options for Roof-top RWH gutters . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Table 3: Cost Per Beneficiary Comparison of Root-top Rainwater 

System Designs Constructed by IRD in Zimbabwe .................. 11 

Figures 

Figure 1. Simulation and Assumptions for the Selected 10,000lt 

Capacity Tank for Households ...................................... 6 

Figure 2. Simulation and Assumptions for the Selected 30,000lt 

Capacity Tank for Schools........................................... 6 

Figure 3: IRD Zimbabwe ....................................................16 

Figure 4: Establishing Responsibility Structures for Water 

Management at Different Levels ...................................17 

Figure 5: WASH Manual & Toolkit............................................18 

Figure 6: Examples of Monitoring Indicators.................................19 

Figure 7: Willingness-to-Pay Study ..........................................21

1 Introduction 

As the global population advances past the 7 

billion mark in 2011, the earth’s already limited 

resources are being placed under increasing 

demand. Water is a resource of critical importance, 

and although significant strides have been made 

towards improving access to water, challenges 

brought about by climate change continue to 

compound water scarcity challenges. According 

to UNICEF and WHO, over 780 million people 

remain in need of improved sources of drinking 

water, with 2.5 billion still lacking improved 

sanitation. 1 A variety of environmentally friendly 

and sustainable techniques have been developed 

in response to challenges associated with the 

provision of clean water supplies. Rain water 

harvesting (RWH) is one such alternative water 

supply source. 

Rainwater harvesting involves the collection and 

storage of rainwater, which is used for domestic, 

agricultural, industrial and environmental 

purposes. 2 It has globally been practiced in 

various forms for centuries, as an alternative to 

unsafe or limited underground water resources. 

Today, RWH is increasingly recognised as a 

relatively low-cost intervention which can be 

employed to improve access to clean water, 

and which has the potential to better people’s 

livelihoods. RWH not only addresses MDG Goal 7 

which underlines improving sustainable access 

to safe drinking water and sanitation; it can also 

play a role in achieving poverty reduction, hunger, 

disease, environmental and gender issues, all 

of which “depend on the availability of water in 

acceptable quality and adequate quantities to 

meet their targets.” 3 

RWH has gained acceptance at local, national, 

and international levels because of this 

potential. Forums such as the Rainwater 

Partnership, which was formed in The Hague 

in 2004, are working to promote the use of 

RWH technologies and its integration in 

water policies across the globe. Stakeholders 

at all levels, including major bilateral donors 

such as USAID, DIFD, EU and AUSAID, as well 

as governments in both the global North 

and South are increasingly supporting 

RWH programs as part of creating long-term 

solutions to water supply and health-related 

issues. 

Roof-Top Rainwater Harvesting Best Practices Guide 1

Today, RWH is increasingly recognised as a relatively low-cost 

intervention which can be employed to improve access to clean water, 

and which has the potential to better people’s livelihoods. 

1.1. Best Practices Guide 

The main objective of this guide is to provide 

organisations implementing roof-top RWH 

programming with a reference tool for roof-top 

RWH best practices. When such best practices are 

followed, roof-top RWH not only adds new sources 

of water, but it can also improve communities’ 

water management capacity and resilience to 

disasters. 

IRD Zimbabwe has developed the Roof-Top 

Rainwater Harvesting Best Practices Guide 

based on practical field experience during the 

implementation of three USAID/OFDA-funded 

programs in Zimbabwe: the Peri-Urban Rooftop 

Rainwater Harvesting (PROOF I & II) programs 

from 2009 and 2011, and the Zimbabwe Rooftop 

Rainwater Harvesting (ZimROOF) program from 

2012 to 2013. The guide is also informed by 

various contributors’ knowledge shared through 

the Regional Roof-Top Rainwater Harvesting 

Workshop for Southern Africa, organised by 

IRD in December 2012. The workshop allowed 

for partners from across the region to highlight 

various applications of roof-top RWH technologies 

and some of the challenges and successes 

associated with it. 

In the first section of the guide, various rooftop 

RWH technologies are introduced, giving 

examples from Southern Africa. The following 

sections put forward best practices for roof-top 

RWH. Firstly, roof-top RWH system hardware is 

discussed, which refers to the physical aspects of 

the entire roof-top rainwater harvesting system, 

including system design, sizing and material 

selection. 

The next section highlights ‘software’ issues; 

referring to behaviour changes and social 

considerations which ensure the sustainability 

of the intervention. Such activities include 

system ownership and participation, trainings 

in system management, and collaboration with 

project stakeholders. 

1 UNICEF and WHO. 2012. Progress on Drinking Water and Sanitation: 2012 Update, p.2. 

2 UNEP and GWP.. Rainwater and the Millennium Development Goals. Available from: www.unep.org/ 

pdf/RWH/intro.pdf . p7. 

3 Ibid p.4. 

2 Roof-Top Rainwater Harvesting Best Practices Guide

2 Background 

2.1. Overview 

Roof-top RWH consists of a range of 

technologies which are used to collect 

and store water. Depending on the chosen 

technology, the harvested water can be used 

for various purposes, including drinking, 

household use and agricultural uses. 

Roof-top RWH presents an alternative water 

source and should be considered in the 

following contexts: 

ɇɇ 

Where there is poor underground water quality 

(possibly due to mining activities or saline 

water) 

ɇɇ 

Where hand pumps are insufficient due to 

the size of population serviced; or where 

there are low water tables. 

ɇɇ 

As a low cost alternative to expensive 

municipal services in high-density 

population areas. 

ɇɇ 

In areas increasingly affected by 

climate change, for instance, semi-arid zones or 

where there is a high degree of fluctuations in 

aquifer levels. 

ɇɇ 

In rural/urban institutions such as schools 

and health clinics where access to a reliable 

water source is a challenge. 

2.2. Rainwater Harvesting 

Technologies 

The choice of technology is context-specific, as 

it depends on needs of the community and the 

feasibility of the technology. 

Existing technologies vary depending on: 

i. The intended use of the water: 

drinking water, household use, 

agricultural purposes 

ii. Method of collection: fog, roof-top, ground, 

sub-surface 

iii. Storage method: these can be divided 

between above ground or sub-surface as 

outlined in Table 1. 

There are advantages and disadvantages 

associated with each roof-top RWH technology. 

Technology selection should be based on needs 

assessments and feasibility studies, which take 

a number of factors into account. Such factors 

include geographical characteristics of the 

area, associated costs of the technology, and 

the ability of the technology to meet the needs 

of the community. Section 3.4.1. on page 7 

shows examples of roof-top RWH technology 

applications from southern Africa. 

Table 1: Roof-Top Rainwater Harvesting Water Storage Methods 

ABOVE-GROUND STORAGE 

SUB-SURFACE STORAGE 

ɇɇPlastic (PVC) tanks 

ɇɇFerro-cement tanks 

ɇɇMasonry tanks (blocks, brick or 

stone) 

ɇɇGalvanized steel tanks (with 

geomembrane lining) 

ɇɇReinforced concrete tanks 

ɇɇReinforced concrete tanks 

ɇɇTanks/Cisterns (with 

geomembrane lining) 

ɇ ɇ Aquifer (groundwater recharge or 

raising groundwater level) 


Typical Roof-top RWH system at a school in Zimbabwe 

3 Hardware: Design Options and Materials 

A roof-top RWH system basically consists of 

a) the roof-top that provides the catchment 

area, b) gutters that collect the water and 

c) a storage tank, where the collected water is 

stored. The design of each of the components 

depends on the available roof-top area, the 

precipitation in the area where the building 

is located and the users’ water consumption 

requirements. 

3.1. Design Considerations 

The decision of which roof-top RWH technology 

to implement depends on a number of factors. 

Consider the following: 

ɇɇ 

Potential volume requirements 

ɇɇ 

Quality requirements 

ɇɇ 

Availability of funds 

ɇɇ 

Materials and skills available locally 

ɇɇ 

Space availability 

ɇɇ 

Rainfall patterns 

3.2. Infrastructure 

Consider the following questions which relate to 

the suitability of roof-top 

RWH systems to the community and the 

existing infrastructure: 

ɇɇ 

Does the house or institution have sound walls/ 

rooflines to add gutter support? 

ɇɇ 

Do suitable roof catchment surfaces exist in the 

community? 

ɇɇ 

Does the household/institution have sufficient 

space for a tank? 

ɇɇ 

Is the site susceptible to animal contamination? 

ɇɇ 

How many people live in the house or use the 

institution, and would it be effective or efficient 

to have a roof-top RWH system installed in that 

context? 

ɇɇ 

Where is the closest water source and are 

there any water quality issues to take into 

consideration? 

3.3. Design Tools 

Correct sizing of the storage tank is critical in 

order to ensure that households or institutions 

have enough drinking water stored to carry 

them through the dry season. An incorrect sizing 

decision can be costly - too large a tank will never 

fill or empty, and too small a tank will fill quickly 

but also empty quickly. Correct sizing requires 

careful consideration of anticipated consumption 

needs during particular periods. 


There are parameters and approaches to be 

considered in the determination of the size of 

the tank. These include: 

ɇɇ 

Demand-side approach: this is a basic 

calculation using consumption rates and 

number of users to estimate the largest storage 

size required. It is important to factor in 

consumption rates during both the rainy and 

the dry season. 

It is possible to use a basic water requirement 

(BWR) which is established by governments. 

In Africa, many countries have adopted 20-35 

litres/capita/day as BWR. 1 An alternative basis is 

presented by SPHERE standards which set the 

average water use for drinking, cooking and 

personal hygiene in any household at least at 15 

litres per person per day. 2 

ɇɇ 

Supply-side approach: a calculation using 

roof area, annual rainfall, run-off coefficient, 

and percentage losses to calculate the likely 

supply that the tank will need to be able to 

accommodate. This is particularly useful where 

there is uneven distribution of annual rainfall. 

ɇɇ 

Computer models: this is based on 

mathematical model of the actual system i.e. 

a simulation. Figure 1 and 2 present typical 

simulations for tank sizes adopted by IRD in its 

rainwater programmes across Southern Africa. 

Figure 1. Simulation and assumptions for the 

selected 10,000lt capacity tank for households 

Tank Simulation 

IRD developed a tool to run tank simulations, 

using daily precipitation data over long periods of 

time and based on assumptions of consumption 

per person during dry/rainy seasons. The 

simulation considers the following factors/ 

assumptions: 

ɇɇ 

Percentage losses (typically around 10%) 

ɇɇ 

Catchment area (roof area) 

ɇɇ 

Number of people using the system 

ɇɇ 

Liters per person per day (in both rainy and dry 

seasons) 

ɇɇ 

Daily average precipitation 

ɇɇ 

Tank size 

By changing the assumptions, you can see 

how the water availability would change 

throughout the year, which can help you 

determine the most advantageous size of tank 

to construct. At certain relatively high usage 

levels, the water tank will often be empty. 

Still, during the rainy season it could 

provide clean water and reduce incidence of 

waterborne disease. 

Key points in tank simulation: 

Point 1: Begin by calculating number and size 

of tanks. The simulation has to be done for 

each tank, and not, for example, from the total 

collection area. 

Point 2: Consider the location (for efficiency, to 

serve the most roofs possible) and the topology. 

Point 3: Efforts must be made for 85 or more 

percentage of days with water in the tank 

(satisfaction ratio). (Cost is a limiting factor.) 

Point 4: All information gathered should 

be verified and validated, for example, 

information on rainfall patterns and 

demographics. 

Figure 2. Simulation and assumptions for the 

selected 30,000lt capacity tank for schools 


3.4. Design Best Practices 

3.4.1. Water Storage Methods 

After having determined the tank size, decide 

what kind of material to use. The table below 

lists design options, and the advantages and 

disadvantages of each for the technologies listed 

in Table 1 on page 3. Section 3.5. highlights 

factors which influence the costs of roof-top RWH 

technologies. Costs vary widely depending on 

many context-specific factors. 

1. Above-ground: Plastic (PVC) Tanks 

Advantages 

ɇɇ 

Off-the shelf stable tanks 

ɇɇ 

Simple installation 

ɇɇ 

Flexibility/adaptability 

Plastic tanks in Swaziland 

Disadvantages 

ɇɇ 

Prone to tampering 

ɇɇ 

High transportation costs 

ɇɇ 

Tanks have predefined dimensions/volume 

ɇɇ 

Medium-high per capita cost. 

ɇɇ 

Should be covered in shade to avoid UV damage 

ɇɇ 

Requires anchors to reduce vulnerability to 

wind/theft 

ɇɇ 

More difficult to clean without dismantling 

the system 

2. Above-ground: Ferro-cement Tanks 

Advantages 

ɇɇ 

Durable if correctly constructed 

ɇɇ 

Relatively low cost 

ɇɇ 

Most materials available locally, low transport costs 

ɇɇ 

Design flexibility 

ɇɇ 

Fixed location (can’t be stolen or blown away) 

ɇɇ 

Less labor intensive than brick or concrete; but more 

so than plastic tanks 

ɇɇ 

Replicable locally, encouraging local participation and 

job creation 

ɇɇ 

Does not require a pumping mechanism to 

extract water 

ɇɇ 

Easy to clean and maintain 

Ferro-cement tank at household in Zimbabwe 

Disadvantages 

ɇɇ 

Requires specialized construction skills 

ɇɇ 

Requires a tank mould to be manufactured 

ɇɇ 

Fixed location means it cannot be relocated 

ɇɇ 

Cracks or imperfections to the concrete are difficult to 

rectify once the tank is complete 

ɇɇ 

Requires quality pit sand for cement mixture 

ɇɇ 

Limited tank size due to construction materials used 


3.4.1. Water Storage Methods continued 

3. Above-ground: Masonry Tanks (blocks, bricks, or stone) 

Advantages 

ɇɇ 

Relatively low cost 

ɇɇ 

Most appropriate when materials are available locally 

ɇɇ 

Little construction training required 

ɇɇ 

Relatively more resistant to corrosion than 

galvanized steel 

ɇɇ 

Community involvement and job creation 

opportunities 

ɇɇ 

Fixed and not affected by weather 

ɇɇ 


extract water 

Stone storage tank in Zimbabwe 

Disadvantages 

ɇɇ 

Relatively more variation in durability and quality 

without adequate planning, quality control, and 

supervision 

ɇɇ 

May require more construction time 

ɇɇ 

Blocks and bricks lack reinforcement and are limited 

in size and less durable 

ɇɇ 

If leaks occur it is difficult to fix without having to replaster 

the entire tank. 

ɇɇ 

Can be more prone to leaks if not constructed to 

standard 

4. Above -ground: Galvanized Steel Tank 

Advantages 

ɇɇ 

Can be relocated 

ɇɇ 

Flexibility in tank dimensions 

ɇɇ 

Can be mass produced 

ɇɇ 

Standardized 

ɇɇ 

Relatively long life (30–50 years) if installed correctly 

ɇɇ 

Can stimulate job creation and support local 

manufacturing industries in country 

ɇɇ 

Can be lined with geomembrane to prevent leaks 

ɇɇ 


extract water 

ɇɇ 

Easy to clean/maintain 

Steel tank in Zimbabwe 

Disadvantages 

ɇɇ 

Can be more expensive than plastic or 

ferro-cement tanks 

ɇɇ 

Susceptible to corrosion if not installed correctly 

ɇɇ 

Heavy and difficult to transport 

ɇɇ 

Not always available in all countries due to lack of 

manufacturing capacity 

ɇɇ 

Subject to damage in transport 


3.4.1. Water Storage Methods continued 

5. Above-ground: Reinforced concrete tank 

Advantages 

ɇɇ 

Durable 

ɇɇ 

Few size and shape limitations 

ɇɇ 

High community involvement 

ɇɇ 

Can be built using locally trained masons 

ɇɇ 

Materials usually found on local market; however might 

not be in close proximity to building site. 

ɇɇ 


extract water 

Steel-reinforced concrete tank in Swaziland 

Disadvantages 

ɇɇ 

Relatively expensive 

ɇɇ 

Requires supervision and quality control 

during construction 

ɇɇ 

Labor intensive 

ɇɇ 

Requires water access during construction phase 

ɇɇ 

Materials may not be locally available (water, sand) 

ɇɇ 

Design requires a specialist 

ɇɇ 

Transport costs can be high 

6. Sub-surface: Reinforced Concrete Tank 

Advantages 

ɇɇ 

Durable when constructed well 

ɇɇ 

Does not occupy much above ground surface area 

ɇɇ 

Easy to maintain once constructed 

ɇɇ 

Can store large amounts of water 

ɇɇ 

Inlet piping can be connected below ground to 

avoid breakages 

Steel-reinforced concrete tank in Mozambique 

Disadvantages 

ɇɇ 

Expensive 

ɇɇ 

Requires skilled labor to construct 

ɇɇ 

Transport costs for materials can be high depending 

on location 

ɇɇ 

Requires a consistent supply of water during the 

construction phase 

ɇɇ 

Requires a pumping mechanism to extract water 

ɇɇ 

Difficult to repair if cracks/leaks appear 

7. Sub-surface: Tank/Cistern for Household Rainwater Storage 

Advantages 

ɇɇ 

Inexpensive 

ɇɇ 

Can provide supplementary water needs 

to households 

ɇɇ 

Does not require a lot of materials 

ɇɇ 

Does not require skilled labor to construct 

ɇɇ 

Ideal for rural households with limited water supply 

ɇɇ 

Does not occupy much space 

Household storage tank in Mozambique 

Disadvantages 

ɇɇ 

Limited size without reinforcement 

ɇɇ 

Cannot store large quantities of water 

ɇɇ 

Needs to be designed to prevent contamination 


3.4.2. Catchment areas 

The majority of roof-top materials are suitable for 

rainwater catchment areas, including iron sheets 

and tiling. Non-corrosive materials such as metals 

are most suitable because they are less prone to 

build up and contamination from debris. 

3.4.3. Gutters 

Gutter design: consider optimal designs 

and sizes for the typical intensity of the 

precipitation, the slope of the roof, and 

how much of each rain event it is important 

to capture. 

Consider building gutters that capture the 

maximum capacity of rain, because later you 

may add tanks as demand increases. 

3.4.4. Connection between gutters and 

tanks 

Metal roof catchment area 

Note: It is widely perceived that water 

collected from asbestos catchment areas may 

be unfit to drink. As remedial action, ensure 

that no holes are drilled into asbestos sheets. 

Instead, fit gutters to the wall structure or 

fascia boards. It is also best to avoid materials 

with contaminants such as lead and asphalt. 

A range of sizes of PVC down piping is 

available, but it introduces a rigid system 

that is not adaptable to flushing and they 

need support because they are susceptible 

to wind. The former can be addressed by 

using an elbow that can unscrew the PVC 

pipe for flushing. 

It is important to use galvanized parts and 

accessories with galvanized gutters. 

Table 2: Materials Options for Roof-Top RWH Gutters 

Material Advantage Disadvantage 

Galvanized steel 

PVC 

Aluminium 

ɇɇ 

Durable 

ɇɇ 

Can be customized to shape and size 

ɇɇ 

Large area allows for maximum water 

collection off roof 

ɇɇ 

Does not rust 

ɇɇ 

Usually available on the local market 

ɇɇ 

Cheaper than galvanized steel 

ɇɇ 

May be suitable for small roof areas. 1 

ɇɇ 

Low maintenance 

ɇɇ 

Easy to install/light weight 

ɇɇ 

Cheaper than galvanized steel 

ɇɇ 

Can be found in local markets 

ɇɇ 

Relatively easy to install as material is 

not heavy 

ɇɇ 

More expensive than other gutter options 

ɇɇ 

Might not be available locally and 

could require additional costs to have 

manufactured 

ɇɇ 

More difficult to install due to the 

weight of the gutters, requires structural 

reinforcement 

ɇɇ 

Prone to cracks and warps (sun exposure 

weakened them) 

ɇɇ 

Is less customizable. 

ɇɇ 

Gutters made from extruded plastic are 

durable but expensive. 2 

ɇɇ 

Typically smaller in size, so greater potential 

for losses off the roof 

ɇɇ 

Prone to rusting and theft 

ɇɇ 

Can more easily lose their original shape 

when exposed to the elements over time 

ɇɇ 

Easy to puncture during transport/ 

installation 


Table 3: Cost Per Beneficiary Comparison of Roof-Top Rainwater System Designs 

Constructed by IRD in Zimbabwe 

Tank Design 

Location 

Cost Per 

Beneficiary 

Notes 

Galvanized Steel Household (peri-urban) $90 18 users per household 

Galvanized Steel School (peri-urban) $44 200 students per tank 

Ferro-cement Household (rural) $78 16 users per household 

Ferro-cement School (rural) $29 150 students per tank 

3.4.5. Design Features for System 

Enhancement 

i. Trap/Filter: There should be a basket or 

filter before the tank or at the outlet to 

filter any debris. 

ii. Angled outlet pipe: such a design serves 

as an additional filter to ensure that any 

debris accumulating at the bottom of 

the tank will be avoided when water is 

collected from the outlet pipe. 

iii. Detachable gutters: this enables selfcleaning 

of the gutter system. Beneficiaries 

are trained to detach before the first rain of 

the season which will flush out any debris, 

and to reattach to start collecting water. 

iv. Tank door: by giving access to the tank, 

this enables sufficient cleaning of the 

inside of the tank according to 

maintenance schedule, 

v. Drainage outlet: for above-the-ground 

tanks, this feature enables removal of 

any accumulated debris during system 

maintenance. 

3.5. Cost of Technology 

The costs of roof-top RWH technologies vary 

considerably. Factors which influence the 

cost include: 

ɇɇ 

System design: capacity, layout and 

topography, 

ɇɇ 

Choice of materials, 

ɇɇ 

Construction/labour costs, 

ɇɇ 

Transportation; 

For cost comparisons between technologies, 

it is important to develop a measurement for 

comparison. Cost per cubic meter can serve 

as a useful means of comparing the 

technology costs. 

Depending on the type of project, developing 

a cost per person over a certain period may 

be more useful. This can vary considerably 

depending on the level of service, for example, 

institution, household, or school. Consideration 

of the number of people served and the demand, 

the ability of the technology to meet water supply 

needs, and the time period over which it can do 

so can enable a more informed decision by both 

project teams and the community. 

Based on the factors mentioned above, Table 

3 highlights examples of cost-per beneficiary 

calculations of various tank designs from IRD’s 

roof-top RWH programs in Zimbabwe to date. 

From the perspective of project management, 

the cost of the initial investment, operational 

costs, and costs of maintenance after the 

project handover should also be considered. 

1 African Development Bank. 2008. Rainwater Harvesting Handbook: Assessment of Best Practises and Experience in 

Water Harvesting, p13 

2 The Sphere Project, ‘Water Supply Standard 1: Access and Water Quantity’, Accessed May 10, 2013 at 

www.spherehandbook.org/en/water-supply-standard-1-access-and-water-quantity/ 


4 Software: Community Ownership 

The incorporation of socio-economic 

considerations is essential to ensuring the 

sustainability of roof-top RWH systems as 

a medium-term solution to water supply 

challenges. The socio-economic factors discussed 

below are linked to community ownership and 

are a prerequisite to the achievement of both 

short-term water supply targets, and in building 

community resilience to long-term health-related 

challenges. 

Participation engenders community 

ownership, which is a priority in all 

development interventions, and must occur at 

every stage of the project. In particular, local 

stakeholders offer an in-depth knowledge of 

the community’s political, economic, social 

and technological status which contributes to 

a program’s design and viability. 

4.1. Beneficiary Selection 

4.1.1. Needs Assessment 

The following assessments should be made when 

planning a roof-top RWH program: 

ɇɇ 

Does the community articulate improved access 

to clean water as not only a need, but as a 

priority? Choose an area based on need, not to 

compete with available alternatives. 

ɇɇ 

What are the needs of the most vulnerable 

members of the communities? include the 

poorer sections of society, women, the elderly, 

disabled, chronically ill, and child-headed 

households. 

ɇɇ 

Assess their access to alternative sources of 

water, their specific needs regarding roof-top 

RWH systems, and their ability to operate and 

maintain the systems. 

ɇɇ 

Establish the basic water requirements (BWR) 

per person. This can be established specific 

to the target area, or a national average can 

be used (In many African countries a BWR of 

20-35 liters/capita/day has been adopted). 1 


Household Level Sub-surface Rainwater 

Storage Tank 

Household Above ground Galvanized Steel 

Storage Tank 

Household storage tank in Mozambique 

Household storage tank in Zimbabwe 

Following best practices for beneficiary selection results in the adoption of the most appropriate oof-top RWH 

technology for the targets. In the rural context of Inhambane in Mozambique, beneficiaries opted for a local 

innovation, the ‘Pote’ (above left), which the program adapted for improved water supply results. This is a low 

cost, easy construction storage option which uses locally available inputs. 

In urban and peri-urban areas near Harare, Zimbabwe, feasibility studies, willingness to pay studies 

and cost effective initial investments into the technology informed the choice of galvanised steel tanks 

(above right). 

SPHERE standards set the average water use for 

drinking, cooking and personal hygiene in any 

household is at least 15 litres per person per day 

in emergency settings. 2 

ɇɇ 

Assess potential drawbacks. Working with the 

community, assess any potential drawbacks 

or conflicts that may arise in relation to rooftop 

RWH systems. It is also useful to draw on 

lessons learnt from previous experiences in 

the community. These experiences can be 

projects by the community itself or projects 

implemented by any other stakeholders. 3 

4.1.2. Technology Selection 

To confirm a choice of roof-top RWH technology, 

project proponents should consider the following 

questions: 

ɇɇ 

What are the existing water supply alternatives? 

Any historical data on water availability and 

quality and on the feasibility of other water 

supply options such as hand pumps will be 

useful. 

ɇɇ 

Why do they need supplementation? Is there 

an established demand for the alternative 

technology and what are the commitments for 

operation and maintenance? 

ɇɇ 

What are the social, economic and 

environmental implications of alternative water 

supply options? For example, considering the 

ability of the community to invest in roof-top 

RWH systems, hand pump, or any public supply 

options; and whether this project or alternative 

water supply options which the community is 

choosing from threaten the livelihood of any 

community members, such as water vendors, or 

centrally supplied water systems in urban areas, 

for example. 4 

ɇɇ 

Project proponents must share roof-top RWH 

technology options with the entire community. 

Such an exercise ensures that the project is a 

demand-led initiative. The community should 

be engaged in order to identify the technology 

that is most feasible and sustainable to their 

context. 

ɇɇ 

Each technology option should be presented 

on equal terms, exploring the merits and 

disadvantages of each. 5 This can be a costbenefit 

analysis of the different technology and 

material options. 

ɇɇ 

Project proponents must advocate for their 

chosen technology option. Having been 

presented alongside alternative technologies, 

social marketing including information 


dissemination can sensitize the community 

on the potential benefits of the project’s 

technology. 

ɇɇ 

As part of advocacy, present a cost-benefit 

analysis with linkages to local institutions. 

This will, for example, make clear the cost of 

treating sicknesses due to drinking water from 

an unprotected water source, as opposed to 

the benefits of investing in clean water supply 

technologies. 

Establishing these factors in selecting a 

technology enables project managers to create 

realistic budgets, strategies for cost recovery and/ 

or levels of subsidies. 6 

4.2. User Contributions 

Involving the communities at all stages, including 

financial and labour contributions is an important 

practice to be incorporated into project plans. 

Beneficiary contributions can be in the form of 

funds, labor, and materials, and they should be 

maximized, sustained, and quantified during 

the planning and design stages. This is an 

exercise to be carried out at all relevant levels: 

household, institutional, or wider community. 

Funds: A community may contribute only a 

fraction of the cost by way of funds, but much 

more in-kind, for example, by giving sand, 

water or bricks. 

Labor: Some roof-top RWH techniques involve 

substantial amount of unskilled labor such as 

earth moving and fetching of local materials. The 

willingness of a community to contribute labor 

in such a case is a substantial contribution which 

affects the cost of the project. It also has a positive 

impact on building community ownership of rooftop 

RWH systems. 

Benefits of assessing the affordability of roof-top 

RWH systems for the target beneficiaries, and 

their willingness to pay for them: 

ɇɇ 

Ability to create correct cost calculations 

ɇɇ 

The assessment will demonstrate the market 

opportunity for local business, and allow 

project to develop any private sector financing 

options. There is need for financial mechanisms 

to support the demand and income levels 

of interested households. The project can 

proceed to build local private sector capacity in 

roof-top RWH system manufacturing- making 

the systems available on the local market, at 

affordable prices to the local community. 

ɇɇ 

Ability to plan for building willingness of 

communities to cost share through, for 

example, advocacy and social marketing. 

ɇɇ 

Enhances a sense of (and practical) project 

ownership by the beneficiaries. 

4.3. Collaboration with 

Government, Local 

Authorities and Partners 

Project success will be greatly enhanced by 

collaborating with all relevant stakeholders 

in the target areas. Projects are often 

implemented in areas where there are preexisting 

or on-going projects by government, 

other organisations, or the community itself. 

Emphasis should be placed on building upon 

existing plans or strategies of the Government 

and partners to use resources more efficiently 

and maximize the collective impact. 

4.3.1. Compliance 

Governments will have national strategies 

for improving water supply and sanitation. 

Projects should work within these, to gain 

support of their project and more simply 

because they share the same overall goal. 

Key guidelines are: 

ɇɇ 

Particularly in rural areas, seek permission and 

involvement of authorities from the highest 

level down, including NGOs and all other local 

stakeholders, and agree on standards from the 

earliest stages. 

ɇɇ 

Get permission to make use of available toolkits 

and curriculums. Establishing a working 

partnership means parties will collaborate to 

adapt them and to incorporate missing content 

where it is identified. 

ɇ ɇ As appropriate, ensure that relevant 

stakeholders are informed and invited to 


Figure 3: IRD Zimbabwe 

Due to perceptions of higher pollution levels in urban areas, national policy in Zimbabwe recognises roof-top 

RWH as an improved water source for rural communities, and not urban communities. IRD, in partnership with the 

Government has completed two urban roof-top RWH programs and shared the results of water quality testing with 

Government and water forums to dispel concerns over water 

quality. 

Pilot projects that have been approved by the government 

are essential to inform policy development and in getting 

government support for expanding their list of approved 

technologies in urban and rural contexts. 

In collaboration with its partners, IRD continues to advocate 

for the safety of roof-top RWH technology by sharing research, 

experience and results with government authorities and water 

sector stakeholders. 

participate in any trainings or demonstrations 

related to the construction, usage and 

maintenance of the roof-top RWH systems. 

4.3.2. Collaboration 

To create better institutional acceptance of rooftop 

RWH, collaborate with institutions already 

working with roof-top RWH. 

ɇɇ 

Discuss your idea and select sites together, and 

continue that throughout the project lifecycle 

up until handover. 

ɇɇ 

Although institutions typically share a common 

end-goal, priorities between stakeholders 

may differ. It is important to understand their 

position vis a vis the project goals. Continually 

seek areas of commonality and opportunities to 

engage and involve authorities. 

ɇɇ 

Document, learn from, and take 

responsibility for setbacks and challenges. 

This is important in building an on-going 

culture of partnership. 

4.3.3. Advocacy 

Stakeholders at various levels are increasingly 

recognising the wide contribution that roof-top 

RWH can make towards meeting developmental 

goals. This is because MDGs, including those 

aimed at reducing hunger and poverty and on 

ensuring environmental sustainability partly 

depend on the availability of water in acceptable 

quality and quantities. 7 

Projects should advocate to authorities 

on the potential benefits of roof-top RWH 

to developmental goals, and encourage 

development or improvements on 

relevant policies that are in line with 

enhancing progress. 

In order to influence national policy where 

necessary, and to gain government support for 

the project, it is important to: 

ɇɇ 

Map and share experiences and results of rooftop 

RWH implementation, 

ɇɇ 

Coordinate with partners and jointly 

advocate to government authorities, 

ɇɇ 

Disseminate information and inform policy 

in national water committee/cluster forums, 

ɇɇ 

Advocate for the inclusion of roof-top RWH in 

all relevant policies (across sectors, i.e., health, 

education), 

ɇɇ 

Support research, policy formulation, and 

any related projects where possible. 

4.4. Gender Considerations 

Gender issues should be considered in the 

designing, planning, and maintenance stages of 

projects to ensure appropriate and sustainable 

systems. 8 Cultural traditions, including gender 

roles in the community should be assessed, and 

the project should work within these traditions. 

The following questions should be considered, 

although the specific questions to ask may vary 

according to the roof-top RWH technology being 

employed: 9 

ɇɇ 

Who controls water sources? 

ɇ ɇ Who is responsible for maintaining the water 

supply? 


ɇɇ 

Who is responsible for managing water use at 

the household level? 

ɇɇ 

What cultural traditions influence women’s 

involvement in water issues? 

ɇɇ 

How can women be involved in the project at 

all stages? 

ɇɇ 

How should women be involved? For example 

by using existing women’s groups, or ensuring a 

quota for their membership in any committees 

formed. 

In many contexts, women play a crucial role 

in water issues as they are the ones who are 

responsible for water management in the 

household. Women and children are also 

amongst the most vulnerable members of 

society in areas where there is poor sanitation 

and risk of disease. Roof-top RWH is likely to 

have a big impact on their day-to-day activities 

and long term development prospects. It is 

very important to include their views and 

needs from the earliest project stages. 10 

Points to remember: 

Point 1: Although women play an important 

role, a survey of the gender dynamics amongst 

the beneficiary community will highlight which 

groups can be harnessed to make the most of the 

intervention. 

Point 2: Roof-top RWH presents an opportunity for 

all family members, across genders, to be trained 

in the importance of clean water supply. This has 

far reaching effects on behaviours impacting 

Figure 4: Establishing Responsibility Structures 

for Water Management at Different Levels 

Household: Each household member should be included in 

WASH training, as this has far reaching effects on building 

long term resilience to disease. Where there are key figures in 

water supply and management at the household levels, 

O & M training should be conducted. 

Institutions/Schools: Find existing groups, for example, 

school development committees, school health clubs; 

or create water management committees within school 

structures. 

Community: Depending on findings from assessments of 

water issues (ownership etc.) in the community, find existing 

groups (health clubs or water management committees 

for example) or form new groups. Any such group can be 

targeted to conduct fundraising for money to maintain the 

system as needed 

health and hygiene and, by extension, other issues 

such as nutrition. 

4.5. System Management and 

Training 

The process of creating a sustainable project 

involves ensuring both the hardware and 

software aspects of roof-top RWH systems are 

understood and implemented by communities. 


Figure 5: WASH Manual & Toolkit 

IRD Zimbabwe developed the Water Sanitation and Hygiene (WASH) Training Manual and Toolkit for Schools with 

roof-top RWH systems as a tool for teachers at schools benefiting from the program to educate their students on 

the usage and care of the system, and for improved hygiene practices. Similar training tools can be developed for 

other projects. 

Available from: www.ird.org/uploads/Rainwater_Harvesting_-_School_Manual.pdf 

Student WASH training at rural schools in Zimbabwe 

This engenders a step away from dependency, and 

towards empowering the community to manage 

the roof-top RWH systems, to form solutions, and 

even to improve on certain aspects of roof-top 

RWH technologies in their communities. 11 

4.5.1. Operation & Maintenance (O&M) 

Planning and Training 

ɇɇ 

Assess beneficiaries’ ability to maintain the 

system, and create appropriate training plan 

ɇɇ 

Set up responsibility structure for the 

roof-top RWH systems. This will vary depending 

on the beneficiary, i.e., household, community 

or institution. 

ɇɇ 

During planning process set up maintenance 

plan and provide appropriate training 

ɇɇ 

Train someone to undertake routine 

maintenance. This should include 

management of the day-to-day operation 

of the water point, and how to repair any 

relatively small problems with the system. 

ɇɇ 

Communities must follow all technical 

recommendations and plan a budget to cover 

maintenance. 

ɇɇ 

It is important to train all beneficiaries on 

operation and maintenance, however extracting 

water from the system should be limited 

to specific individuals who have received 

specialized O&M training. 

4.5.2. Planned Maintenance and 

Management 

ɇɇ 

Create a plan and schedule for cleaning 

roof and tank. The schedule needs to 

accommodate rainfall patterns. 

ɇɇ 

Plan for regular water quality testing, and to 

monitor any water loss. 

ɇɇ 

Create a monitoring sheet to record inputs 

and outputs, along with dates. 

ɇɇ 

Identify the person to be trained to manage the 

management system. 

4.5.3. WASH Training 

Devise appropriate training curriculum or 

methods, including developing manuals and 

charts to cover materials provided in trainings. 

These may differ at various levels as follows: 

Household: 

ɇɇ 

Educate household on water treatment and 

testing options, and let households choose the 

method they prefer. 

ɇɇ 

Train on how to manage the resource (this is 

important to ensure water availability through 

dry spells, and also considering that many 

household beneficiaries share water with 

neighbours for example). 

ɇɇ 

There are several household level training 

methodologies that can be used in conjunction 


with the installation of a roof-top RWH system. 

For example, PHHP (participatory health 

and hygiene promotion) advances beyond 

PHAST (participatory hygiene and sanitation 

transformation), and is more focused more on 

households. 

Institutions/schools: 

Schools offer a conducive environment 

to train large volumes of beneficiaries 

including students and members of the wider 

community. Methods for training at schools 

may include: 

ɇɇ 

Participatory health and hygiene 

promotion (PHHP) 

ɇɇ 

Schools offer opportunity to make use 

of available toolkits and curriculums. In 

collaboration with education authorities, 

these can be adapted to incorporate missing 

content where the need is identified. 

Community: 

It is important to identify existing water 

management structures, organizations or health 

clubs within the benefitting community. Once 

responsibility structures for roof-top RWH systems 

at the community level are established, these 

can guide the selection of target groups for 

community WASH trainings. Health clubs, local 

clinics and other community centres (including 

church-based groups) should be trained on the 

various WASH issues. WASH objectives included 

improving water management capacity, resilience 

to catastrophe through training, and access to 

new sources of water. Key issues for WASH training 

include: 

ɇɇ 

Importance of latrine usage: this can be 

emphasised through the Community Led Total 

Sanitation methodology (CLTS). This community 

mobilization methodology works to eliminate 

open defecation by facilitating self-appraisals by 

the community, and encouraging them to take 

action to eliminate the practice. 12 

ɇɇ 

Health and hygiene issues including hand 

washing and water treatment methods. 

ɇɇ 

Contingency planning for disaster preparedness. 

ɇɇ 

Community mapping of resources: water 

management is important. Identifying existing 

water resources should be a community-led 

process. 

ɇɇ 

Solid waste management 

ɇɇ 

Separation of water sources accessed for human 

vs. animal consumption. 

4.6. Monitoring and Evaluating 

Develop a baseline with indicators that can be 

monitored, reported on and evaluated. These 

are formed in relation to the specific goals of the 

project. Examples of such indicators are outlined 

below. 

Water Supply Indicators: 

ɇɇ 

Distances to water points before and after the 

project intervention; 

ɇɇ 

Time spent collecting water. This can reflect the 

impact of an intervention on those responsible 

for water management at the household level. 13 

ɇɇ 

Access to water by the ill or disabled 

ɇɇ 

What source does the water come from? 

ɇɇ 

Safety for drinking – quality of water. 

Health indicators: 

ɇɇ 

Incidence of waterborne diseases; data available 

from numerous sources, e.g. hospitals, clinics 

and schools (using school absence of students 

and staff). Diseases 

to track may include cholera, typhoid, 

and bilharzias. 

Figure 6: Examples of Monitoring Indicators 

ɇɇ 

Percentage of water points with 0 bacteria coliforms, e-coli 

ɇɇ 

Number and percentage of water points with residual chlorine levels exceeding 0.2 mg/L 

ɇɇ 

Percentage of beneficiaries practicing good hand-washing techniques 

ɇɇ 

Percentage of beneficiaries demonstrating correct usage and storage of water 

ɇɇ 

Percentage reduction in diarrheal incidence among students 

ɇɇ 

Percentage increase water usage of target population in liters per person per day 

ɇ ɇ Number of people with access to rehabilitated/established water points 

Percentage increase in water usage/availability for beneficiaries 


ɇɇ 

Sanitation and Hygiene practices: are they 

being implemented. For example: hand 

washing, point-of-use treatment, latrine usage, 

solid waste management, food preparation 

techniques. Water quality monitoring— 

including type of container which is used to 

transport water from the roof-top RWH system 

to the usage point, and where it is stored. 

Other: 

ɇɇ 

Advocacy indicator: Rainwater harvesting 

included in national water policies and 

strategies as accepted standard designs 

and approaches. 14 

ɇ ɇ O&M performance data of the established rooftop 

RWH structures (water quality for drinking 

purposes being maintained, reservoir capacity 

maintained, caretakers being paid, small scale 

repairs such as leaking taps, broken gutters etc. 

being attended). 

1. African Development Bank. 2008. Rainwater Harvesting Handbook: Assessment of Best Practises and Experience in 

Water Harvesting, p.13. 

2. The Sphere Project, ‘Water Supply Standard 1: Access and Water Quantity’, Accessed May 10, 2013 at http://www. 

spherehandbook.org/en/water-supply-standard-1-access-and-water-quantity/ 

3. Organisation of American States , “Rainwater harvesting from rooftop catchments” http://www.oas.org/dsd/ 

publications/Unit/oea59e/ch10.htm 

4. Ibid. 


Water Harvesting. p.17. 

6. Ibid. p.11. 

7. UNEP and GWP. [no date]. Rainwater and the Millennium Development Goals. Available from: www.unep.org/pdf/ 

RWH/intro.pdf , p.7. 

8. Agromisa Foundation and CTA. 2006. Agrodok 43: Rainwater harvesting for domestic use. Available from: http:// 

journeytoforever.org/farm_library/AD43.pdf pp.22-23. 



10. Ibid. p.12. 

11. Ibid. p.10. 

12. Institute of Development Studies, ‘The CLTS Approach’, Accessed May 9, 2013 at 

http://www.communityledtotalsanitation.org/page/clts-approach 



14. Ibid. 


5 Replicability Factors 

The application of rainwater harvesting 

technologies varies widely, according to 

numerous factors which are context-specific. 

Factors enabling replicability of any roof-top RWH 

technology include the following: 

ɇɇ 

High degree of community involvement 

ɇɇ 

Locally available skills 

ɇɇ 

Cost 

ɇɇ 

Availability of materials 

ɇɇ 

Suitable climactic conditions 

ɇɇ 

Market/demand for additional tanks 

ɇɇ 

Resource mobilization from multiple 

stakeholders 

ɇɇ 

Training and demonstrations 

For project success and sustainability, proponents 

must consider these in the planning/inception 

stages. 

A key factor in ensuring sustainability of the 

roof-top RWH systems is community ownership. 

Projects teams must look for ways to extend 

the impact of the intervention, post project 

handover. Conducting a willingness-to-pay study 

is recommended to help establish the feasibility 

of the project, and the prospects for increasing 

the adoption of roof-top RWH as a water supply 

solution after project completion. 

Figure 7: Willingness-to-Pay Study 

ɇɇ 

A willingness-to-pay study, conducted by 

IRD Zimbabwe, concluded that 5% to 15% of 

Chitungwiza’s 300,000 homeowners are willing to 

pay more than $1,000 for a standard Roof-top RWH 

system, while up to 25% of the homeowners are 

willing to pay $500. 

ɇ ɇ This indicates the potential demand of 6,000 to 

18,000 Rainwater Harvesting Units equating to $6-8 

million in revenue for local businesses and local 

industry. 

Willingness-to-pay studies help projects to 

develop strategies for: 

ɇɇ 

Creating linkages with credit for homeowners 

to finance the systems, for example, through 

affordable payroll deductions. Through links 

to financial institutions, it is possible to create 

credit schemes for people to purchase an entire 

system and pay back over a period of time. 

ɇɇ 

Establishing the need for financial mechanisms 

to support the demand and income levels of 

interested households 

ɇɇ 

The need to demonstrate the market 

opportunity. Links with private sector 


6 References 

companies to create “one stop shop” for 

constructing/installing a system at a household. 

African Development Bank. 2008. Rainwater Harvesting 

Handbook: Assessment of Best Practises and 

Experience in Water Harvesting. Available from: 

www.pseau.org/outils/.../bafd_rainwater_ 

harvesting_handbook.pdf 

Agromisa Foundation and CTA, 2006. Agrodok 43: 

Rainwater harvesting for domestic use. Available 

from: http://journeytoforever.org/farm_library/ 

AD43.pdf 

Institute of Development Studies, ‘The CLTS Approach’, 

Accessed May 9, 2013 at http:// 

www.communityledtotalsanitation.org/page/cltsapproach 

Organisation of American States, Rainwater harvesting 

from rooftop catchments. Available from: http:// 

www.oas.org/dsd/publications/Unit/oea59e/ch10. 

htm 

Practical Action, no date, Rainwater Harvesting: 

Technical Brief. Available from: http://practicalaction. 

org/docs/technical_information_service/rainwater_ 

harvesting.pdf 

UNEP and GWP. Rainwater and the Millennium

Roof-Top Rainwater Harvesting Best Practices Guide - International ...

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