Western Region - Drinking Water Inspectorate - Defra

Drinking water
2011
Public water supplies in the
Western region of England
July 2012
A report by the Chief Inspector of Drinking Water

W estern re gion
Drinking water 2011
Western region of England
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Dri nking water 20 11
Published by
Drinking W ater Inspectorate
Area 4a
Ergon House
Horseferry Road
London
SW 1P 2AL
Tel: 0300 068 6400
W ebsite: http://www.dwi.gov.uk
© Crown Copyright 2012
ISBN: 978-1-905852-64-2
Copyright in the typographical arrangement and design rests with the Crown.
This publication (excluding the logo) may be reproduced free of charge in any
format or medium provided that it is reproduced accurately and not used in a
misleading context. The material must be acknowledged as Crown copyright with
the title and source of the publication specified.
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Contents
Overview of drinking water quality in the region 4
Water supply arrangements 9
Drinking water quality testing 11
Drinking water quality results 12
Microbiological quality 12
Chemical quality 21
Maintaining water quality in distribution 32
Maintaining water quality at the tap 36
Drinking water quality events 41
Technical audit activity 44
Annex 1: Further sources of information 50
Annex 2: Glossary and description of standards 51
Annex 3: Drinking water quality events in the region 64
Annex 4: Planned drinking water quality improvements 72
Annex 5: Competition in the water industry 75
Annex 6: Water company indices 77
Annex 7: Information relating to public water supplies 84
published by the Inspectorate in 2011
Annex 8: Distribution of private water supplies 86
Drinking Water 2011 is the annual report of the Drinking Water Inspectorate and
comprises reports covering public and private water supplies.
Public supplies – This part describes drinking water quality in the Western region. The
Inspectorate also publis hes a series of companion reports for othe r regions of England
(Central and Eastern, Northern, and London and South East regions) and a separate
report for Wales.
Private supplies – A summary of information on private water supplies is reported for
England and Wales.
All parts are available on the Inspectorate’s websit e www.dwi.gov.uk
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Percentage of tests failing
Dri nking water 20 11
Overview of drinking water quality in the region
Drinking Water 2011 is published as a series of seven reports, five of
which cover public water supplies and two describe private water supplies.
Each report presents information about drinking water quality for the
calendar year of 2011.
The improving national trend in the quality of public water supplies since
1990 is shown in Figure 1. Compliance with the standards in the EU
Drinking Water Directive now stands at 9 9.96% for public supplies in
England, however, the results for private water supplies in England are of
concern with 7.2% of tests failing to meet the standards in 2011.
Figure 1: Percentage of tests from public and private supplies failing
the drinking water standards (England and Wales combined)
10
9
8
7
6
5
4
3
2
1
0
England and Wales public supplies England and Wales private supplies (data not available before 2010)
Footnote:
Public supp lies: Perc e ntag e of tests failing is calcul a ted for sam ples taken in zones .
Private sup plies: Perc entage of tests failing is calcul ated for all sam ples .
At the end of 2010, the regulations covering both public and private water
supplies were changed to address deficiencies in the transposition of the
Drinking Water Directive into national law . The infraction case by the
European Commission was subsequently closed in September 2011. The
purpose of the 2010 amendments to the regulations was twofold: to make
enforcement mandatory for failures of standards in public buildings and to
make clearer the duty to minimise disinfection by -products.
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In 2011, across 29 companies, over 43,000 tests were carried out at public
buildings out of which 35 tests failed to comply with one or more of the
standards or indicator parameter values (Coliform bacteria, E.coli, iron,
lead, nitrite, taste, odour and turbidity). In the W estern region failures that
arose due to arrangements in the public buildings are described in the
Maintaining water quality at the tap section.
In relation to how well companies are complying with the requirement to
keep disinfection by-products as low as possible, in 2011 across England,
the annual average figure for total trihalomethanes was 9.9µg/l in
groundwater supplies and 27.9µg/l in surface water supplies compared to
the standard of 100µg/l. For more information about trihalomethanes in the
Western region see the Chemical quality – Disinfection by-products
section.
This report describes the key facts about the quality of public water in
the Western region, which is served by seven water companies delivering
water supplies to over four and a half million consumers. In addition local
authorities have identified 14,858 private water supplies in the Western
region. Details of the quality of these private supplies can be found in the
separate report Drinking Water 2011 – Private water supplies in England.
Annex 8 of this report maps the location of private supplies reported to the
EU under the Drinking Water Directive. It also shows small shared supplies
used only for domestic purposes.
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The results of testing of public supplies in 2011 demonstrated that the
overall quality of drinking water in the Western region was good. The
figure for compliance with drinking water standards at consumers’ taps
was 99.97%, the same as reported in 2010 and above the industry
average. This figure is made up of the results of all the tests for 39
parameters with European or national standards. Across the region , all
tests for 29 out of 39 parameters gave satisfactory results. Failures were
reported for E.coli, odour, taste, aluminium, iron, manganese, lead,
turbidity, nickel, and one pesticide (Mecoprop (MCPP)).
Table 2 puts the failures into context with respect t o the other regions of
England and W ales.
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Table 2: Parameters exhibiting one or more failure of a standard
England
Parameters
Wales
Central
and
London
and South
Northern
Western
Eastern
East
region
region
region
region
Microbiological parameters
E.coli
Enterococci
Physical/chemical parameters
Odour
Taste
Aluminium
Iron
Manganese
Lead
Turbidity
Nickel
Benzo(a)pyrene
Copper
Nitrite
Bromate
Chlortoluron 1
Clopyralid 1
Glyphosate 1
MCPA 1
MCPP 1
Metaldehyde 1
Propyzam ide 1
1 These parameters are pesticides.
When the Western region is judged by the Inspectorate’s four indices of
water quality performance, which look in turn at water treatment (covered
by two indices, process control and disinfection), service reservoir integrity
and network maintenance, the changes in 2011 were improvement in the
figures for process control (>99.99%) and disinfection (99.99%). Figures
for service reservoir integrity (99.97%) remained the same and the network
maintenance figure (99.82%) was lower than last year. Nevertheless , in
this region all indices were at or above the industry figure except for the
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Dri nking water 20 11
network maintenance index. Individual water company figures are reported
in Annex 6.
Across the region, in 2011, there were slightly more events affecting water
quality overall (46 compared to 42 in 2010). Only around one-quarter of
these were of a type that necessitated a detailed investigation by an
inspector and this compares favourably with the industry overall. The
number of each event type can be found in the Drinking Water Quality
Events section together with learning points from other event assessments
by the Inspectorate. In 2011, there were no serious events affecting
consumers in the Western region.
Turning to planned improvements in drinking water quality in the region,
in 2011 the Inspectorate confirmed the need for additional work at Empool
works (WSX) and Thruxton and Compton boreholes (CHO). Companies in
the region are committed to complete the work summarised in Annex 4
during the AMP5 period (2010 –2015).
In 2011, the Inspectorate provided the water industry with advice and
guidance on nine topics to enable companies to comply with the drinking
water regulations. In addition, nine research projects were published by
the Inspectorate to support the industr y in carrying out regulatory risk
assessments (see Annex 7).
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Water supply arrangements
Seven water companies supply drinking water in the Western region:
Bristol Water (BRL), Cholderton and District W ater (CHO), Se mbcorp
Bournemouth Water (SBW), South West Water (SWT) and Wessex Water
(WSX). Two inset appointments, Veolia Water Projects (VWP) and
SSE Water (SSE) supply consumers in the Tidworth area and Old Sarum,
Salisbury respectively.
Figure 3: Map illustrating sources of drinking water by zone across
the region
Much of the water in the region is derived from surface water (7 1%)
abstracted from rivers such as the Severn, the Hampshire Avon, Dart, Exe,
Fowey, Tamar and the Dorset Stour. There is a major transfer of water into
the region via the river Severn from reservoirs in Wales that provide half
the daily supply for English consumers in the Bristol Water area.
Additionally, the upland areas of Bodmin Moor, Dartmoor, Exmoor and the
Mendips are important catchments for water resources in the region.
Surface water is drawn from many reservoirs, including Chew Valley Lake,
Clatworthy, Colliford, Roadford and W imbleball. Groundwater provides a
valuable resource (27%) in the region, with many boreholes drawing water
from the chalk aquifer of the Wessex basin. The Permian a nd Triassic
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Dri nking water 20 11
sandstone aquifer in the Otter Valley is also an important groundwater
source for East Devon. Cholderton and District Water, relies exclusively
on the chalk aquifer of the Wessex basin. Across the region, a small
proportion of water supplies ( 2%) can be drawn from either surface or
groundwater sources.
Private water supplies in the region are widely distributed across the
area with large concentrations in the Dartmoor and Exmoor regions .
These private supplies are more reliant on groundwater (63%) than the
public supplies in the area (27%).
Summary facts about the drinking water supply infrastructure of
the region are given in Table 4 with outline geographical and
demographic information.
Table 4: Key facts about public and private water supply arrangements
in the Western region
Public supplies
Population supplied
Water supplied (l/day)
Abstraction points
Treatment works
Service reservoirs
Water supply zones
Length of mains pipe (km)
4,529,770
1,224 million
348
155
809
188
36,110
Private supplies
Population supplied
Water supplied (l/day)
Approximate number of private
water supplies
Total number of local authorities
66,317
40 million
14,858
36
Water composition
Surface sources
Groundwater sources
Mixed sources
71%
27%
2%
Water composition
Surface influenced supplies
Groundwater sources
Rainwater
37%
63%

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Drinking water quality testing
Throughout 2011, water companies sampled drinking water across the
region to test for compliance with the drinking water regulations. More than
one-third (34%) of the tests were carried out on drinking water drawn from
consumers’ taps selected at random. For monitoring purposes, company
water supply areas are divided into zones . Sampling in zones at
consumers’ taps is risk based with the number of tests being higher in
zones with a large population (maximum 100,000). Other sample locations
are water treatment works and treated water (service) reservoirs.
Collectively, the seven water companies carried out a total of 614,422
tests during 2011. Only 131 of these tests failed to meet the standards
set down in the regulations or exceeded screening values.
Table 5: Number of tests carried out by companies in the region
Place of sampling
Number
Company
Water
treatment
works
Service
reservoirs
Consumers’
taps (zones)
of tests
per
company
Estimate of
population
Bristol W ater
26,921
(17)
50,419
(165)
49,312
(52)
126,652 1,155,305
Cholderton
and District
W ater
737
(2)
312
(1)
370
(1)
1,419 2,100
Sembcorp
Bournemouth
W ater
14,170
(7)
6,182
(20)
17,851
(10)
38,203 430,000
South W est
W ater
48,521
(31)
85,297
(282)
74,139
(32)
207,957 1,696,000
SSE W ater
0
(0)
0
(0)
389
(1)
389 685
Veolia W ater
Projects Ltd
1,252
(2)
1,560
(6)
652
(1)
3,464 8,000
W essex W ater
75,315
(85)
92,907
(299)
68,116
(91)
236,338 1,237,680
Region
overall
166,916
(144)
236,677
(773)
210,829
(188)
614,422 4,529,770
Num bers in brackets reflec t the num ber of wo rk s , reser voi rs or zo nes op er ated by that com pany in
the re gion in 201 1. Som e com panies are perm itted to c arr y out som e tests on sam ples taken from
s uppl y po ints rat he r than f r om consum ers ’ t aps.
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The regulations require companies to test for specified parameters at
prescribed frequencies. Most of the testing is f or parameters with
European or national standards, however, water companies are also
required by the regulations to test for other parameters, such as
ammonium, sulphate and colony counts.
A summary of the results of testing by compan ies for each parameter can
be found on the Inspectorate’s website (www.dwi.gov.uk) and on the CD
accompanying this report. Additionally, the Inspectorate publishes
annually, the performance indices for each company in Annex 6.
Drinking water quality results
The key water quality results for the Western region are presented in two
tables, one showing the results for microbiological parameters (Table 6),
the other dealing with chemical and physical parameters (Table 8). The
microbiological quality of water is discussed first. Companies report all the
results of the tests on a monthly basis to the Inspectorate. Also, tables in
Annex 6 describe the drinking water quality performance indices of each
company supplying in the region.
Microbiological quality
To protect public health, microbiological standards have to be met at each
individual treatment works and service reservoir. The significance of the
individual test results for each microbiological parameter at each location
varies and a single positive result cannot be interpreted without other
information. All companies are expected to follow best practice as set
out in The Microbiology of Drinking Water published by the Standing
Committee of Analysts (SCA) which can be found by visiting the
Environment Agency’s website (www.environment -agency.gov.uk).
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Table 6: Microbiological tests
The number of tests performed and the number of tests not m eeting
the standard
Parameter
Current
standard
Water leaving water treatment works
Total
number
of tests
Number of
tests not
meeting
the
standard
E.coli 0/100ml 23,464 2 SW T (2)
Coliform bacteria 0/100ml 23,464 9
Clostridium
perfringens
0/100ml 5,621 5
Turbidity 1 1NTU 23,512 5
Water leaving service reservoirs
Additional
information
BRL (1), SBW (2),
SW T (5), W SX (1)
BRL (1), SBW (1),
SW T (3),
BRL (1), SBW (2),
SW T (2),
E.coli 0/100ml 39,522 3 SW T (2), W SX (1)
Coliform bacteria
0/100ml in
95% of tests
at each
reservoir
Water sampled at consumers’ taps
39,522 20
E.coli 0/100ml 12,582 6
Enterococci 0/100ml 1,466 0
BRL (4), SW T (6),
W SX (10)
All reservoirs in
the region meet
the 95%
compliance rule
BRL (1),SBW (3),
SW T (1), W SX (1)
1 Turbidity is a critical control parameter for water treatment and disinfection.
E.coli at works and service reservoirs
In 2011, out of a total of 23,464 tests at works, E.coli was detected in two
samples (2 SWT) and there were just three E.coli failures (2 SWT, 1 WSX)
out of a total of 39,522 tests at service reservoirs . This is an improvement
compared to 2010 when there were three detections of E.coli at works and
the same number in service reservoirs.
On detecting E.coli, companies are required to act promptly to pro tect
public health. Their immediate response when finding E.coli at a works or
service reservoir is to sample again, and more widely, to confirm that
water being received by consumers is safe. In 2011, these additional tests
gave satisfactory results in all cases and there were no subsequent E.coli
failures.
E.coli was detected in a sample taken from Dotton works (near Sidmouth)
in June and also in a sample taken on the same day from Blackhill service
reservoir, a reservoir fed from Dotton works via Capel Lane service
reservoir. In both cases the analyst recorded the presence of brown
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Dri nking water 20 11
particulate matter in the samples. In response, South West Water checked
treatment performance at the works, including disinfection, and externally
inspected both reservoirs. Nothing untoward was found, but the residual
chlorine level in water leaving Dotton works was increased. At that time
the company believed that the failures were linked to contamination of the
sample bottles, however, in September, after a further coliform failure at
Dotton works, the company found a number of significant defects,
including leaks in the roof of the treated water tank and this was removed
from service until remedial works were completed. The Inspectorate was
disappointed to note that the company failed to identify these defects when
investigating the earlier E.coli failures and reminded the company of the
need for investigations to be wide ranging and comprehensive. A new
membrane was applied to the roof of the tank which was flood tested on
5 December 2011 and the tank was subsequently returned to service.
In December 2011, E.coli was detected in a sample collected from St Cleer
works (near Liskeard) and also on the same day in a sample taken from
Bodelva service reservoir. The reservoir is not hydraulically linked to St.
Cleer, but instead receives water from Restormel works via Charkhill
service reservoir. Follow-up tests and enhanced monitoring by South West
Water were all satisfactory. In early 2012 , the company took Bodelva
service reservoir out of service for inspection and cleaning and similar
action was scheduled for the treated water tank at St Cleer commencing
mid April 2012 after essential enabling works (pump replacement at
Bastreet works).
During October, a sample collected by Wessex Water from Two Ash
service reservoir (near Chard) contained E.coli and coliforms. Two Ash
service reservoir had been inspected and cleaned in February 2010 when
the structure was deemed satisfactory. The company implemented
enhanced monitoring and detected coliforms again in November , triggering
an external inspection which flagged concerns about the sampling facilities
as the kiosk was sited next to a hedge with overhanging vegetation with out
protection from the elements and passing cars using the road. Wessex
Water upgraded the sampling facilities in December .
Companies are reminded of their regulatory duty to ensure samples are
representative of water in supply and the need to pay closer attention to
all aspects of sampling (facilities and staff).
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Table 7: Detection of E.coli and Enterococci at treatment works,
service reservoirs and consumers’ taps
Company
E.coli in
water
leaving
treatment
works
E.coli in
water
leaving
service
reservoirs
E.coli at
consumers’
taps
Enterococci
at
consumers’
taps
Bristol W ater 0 – 3,823 0 – 8,402 1 – 3,120 0 – 387
Cholderton and
District W ater
Sembcorp
Bournemouth
W ater
0 – 103 0 – 52 0 – 12 0 – 4
0 – 1,772 0 – 1,031 3 – 1,106 0 – 81
South W est W ater 2 – 6,887 2 – 14,232 1 – 4,452 0 – 380
SSE W ater 0 – 0 0 – 0 0 – 13 0 – 4
Veolia W ater
Projects Ltd
0 – 206 0 – 312 0 – 24 0 – 8
W essex W ater 0 – 10,673 1 – 15,493 1 – 3,855 0 – 602
Region overall 2 – 23,464 3 – 39,522 6 – 12,582 0 – 1,466
Note: Results ar e sho wn as the num ber of positive tests – the total num b er of tests.
Coliform bacteria at works
Testing for coliform bacteria gives reassurance that water entering the
supply was treated adequately to remove bacterial and viral pathogens.
Repeated occurrences of coliform bacteria in samples from the same
works in one year are thus of concern and require action to be taken.
In 2011, this situation occurred at three sites: Tottiford works, Dotton
works (SWT) and Alderney works (SBW). Both sites failed the coliform
standard on two occasions during 2011.
There were two detections of coliforms at Dotton works (near Sidmouth),
operated by South West Water during June and September (see the E. coli
at works section).
Coliforms were reported in samples from Tottiford works near Bovey
Tracey in successive months (May and June). South West Water found and
fixed a leaking sample tap and scheduled an internal inspection of the
west cell of the treated water tank for early July. The inspection revealed
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Dri nking water 20 11
ingress of rainwater in the northwest corner of the tank, pooling of wa ter in
a drainage channel and the roof membrane was damaged. Repairs to the
west cell of the treated water tank were completed on 26 July and the tank
returned to supply a week later following cleaning and sampling. Due to
work at the site to construct new rapid gravity filters, the east cell of the
tank could not be taken out of supply immediately. The repairs to this cell,
which included the application of a liquid membrane to the jointed areas of
the roof slab, were carried out in February 2012 and the e ast cell was back
in service in mid-March.
During February 2012, there was an event at Tottiford works when a
sample result of >100 E.coli was reported. The east cell of the treated
water tank was out of use at this time and treatment was operating
normally. South West Water found particulate matter in the sample bottle
and concluded the sample was not representative of water entering supply.
The Inspectorate has noted that it is not uncommon for failures to occur
at sites where assets are being refurbishe d or modified and companies
should take risks associated with such activities into account when
investigating failures.
In September, Wessex Water detected coliforms at Clarendon Park works
(near Salisbury). The company found that the sample tap was corroded
and there was a leak on the sample line . After replacement of the tap the
non-return valve was found to be faulty and further repairs were carried
out. The Inspectorate expects companies to have in place a proactive
programme of maintenance of sampling facilities.
During 2011 there were coliform failures at Alderney works operated by
Sembcorp Bournemouth Water. Following the first failure in July the
Inspectorate requested additional data and observed a rise in raw water
coliform numbers in the preceding week. The company attributed the
second failure to sample tap defects. The Inspectorate reported in 2010,
on serious integrity issues at this site where the filters are situated above
the contact tank. The company had failed to make a link between failure s
in the downstream network with known integrity issues at the works. Again ,
in 2011, there were coliform failures in consumer tap samples in zones fed
by this works (see the Maintaining water quality at the tap section). The
Inspectorate remains concerned about the company’s approach to the
investigation of failures, which appears narrow in scope and lack s analysis
of quality and asset condition data.
During December, coliforms were detected at Banwell works (near W eston -
Super-Mare). Bristol Water took follow-up samples from downstream
reservoirs, but not from properties fed directly from the works. Companies
are reminded that it is a regulatory duty to carry out comprehensive
sampling and analysis in response to adverse results. Enforcement action
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W estern re gion
will be taken if further evidence demonstrates that Bristol Water is not
complying with Regulation 10.
The Inspectorate has noted that coliform bacteria were found in nine
(1 BRL, 2 SBW, 5 SWT, 1 WSX) samples from treatment works in the
Western region during the year and this information will be taken into
account during the Inspectorate’s risk -based programme of technical audit.
Clostridium perfringens
This organism is a spore-forming bacterium that is exceptionally resistant
to unfavourable conditions in the water environment, such as extremes of
temperature and pH, and disinfection processes such as chlorination and
ultraviolet light. It is a normal component of the intestinal flora of up to
35% of humans and other warm-blooded animals. These characteristics
make it a useful indicator of either intermittent or historical faecal
contamination of a groundwater source or the performance of a surface
water filtration plant. The detection of any Clostridium perfringens should
trigger an investigation by the water company.
In 2011, out of 5,621 tests taken across the W estern region, five did not
meet the specified value (1 BRL, 1 SBW, 3 SWT).
South West Water detected Clostridium perfringens in samples collected
from Allers works (February), Pynes works (June) and Drift works
(October). The company implemented enhanced monitoring at each site.
To date nothing untoward with treatment performance has been found.
The Inspectorate expects the company to review and update the relevant
regulatory risk assessments to record this information, particularly the use
of monitoring as the control measure .
In June, Bristol W ater identified Clostridium perfringens in a sample taken
from Littleton works (near Bristol). Clostridium perfringens was recorded
in raw water samples before its occurrence in the treated water sample;
however, this did not result in a review of the regulatory risk assessment.
This was not the only case in 2011 when the Inspectorate had reason to be
critical of Bristol Water’s approach (see the Coliforms at works section).
Sembcorp Bournemouth W ater reported Clostridium perfringens in a
consumer tap sample collected from the Alderney North supply zone. This
sample also contained E.coli and coliforms. A fittings inspection identified
a number of irregularities at the property including an outside tap with an
attached hose. The integrated non-return valve had failed allowing
backflow and a sample taken from the hose contained high levels of
coliforms, E.coli and Clostridium perfringens. A follow-up sample after
these faults had been rectified was satisfactory. This is important evidence
of the risk from hoses on outside taps where effective backflow protection
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Dri nking water 20 11
is absent and the Inspectorate considers it should be shared more widely
to assist the industry and the Water Regulations Advisory Service in
dealing with certain groups of property owner who object to enforcement
of the backflow protection element of the fittings regulations asserting that
backflow risks are not proven and the remedies burdensome.
Turbidity at works
Turbidity is a measure of how much light can pass through water and
indicates the condition or ‘cloudiness’ of water. Turbidity is caused by
particles suspended in the water and is an important critical control
measure of the performance of disinfection. Turbidity is measured at two
points in the water supply chain, at treatment works where a value of
1NTU applies and at consumers ’ taps where the standard of 4NTU applies.
The following discussion focuses on the results of sa mples taken at
treatment works.
The number of turbidity failures across the region i n 2011 was five (1 BRL,
2 SBW, 2 SWT) and this continues the improvement in previous years
(17 in 2009, 6 in 2010).
In June, a sample taken from Knapp Mill works (near Bournemouth)
exhibited a value of >1NTU. Sembcorp Bournemouth W ater had taken
duplicate samples and the other sample gave a satisfactory result of
1NTU at Alderney works
in December was limited to checks of on -site monitors and duplicate
sampling (in this case the duplicate sampl e was lost so there was no
validation evidence). Both of these situations lend further weight to the
Inspectorate’s concerns about the narrow focus of investigations carried
out by Sembcorp Bournemouth Water (see the Coliforms at works section).
At Banwell works (near Weston-Super-Mare), Bristol W ater attributed a
turbidity value of >1NTU in August to flow changes following maintenance
activities on slow sand filters. Consequential changes in flow rate through
the combined outlet chamber appear to have disturbed sediment at this
location as there was no contemporaneous increase in turbidity at the
outlet of each of the individual slow sand filters.
Following a turbidity value of >1NTU in a sample from Stithians works
(near Falmouth) in January, South West Water identified a link to issues
with the control system settings on start up of the works following a power
outage caused by a lightning strike. There was a loss of control of pH
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W estern re gion
correction and the turbidity was caused by lime particles. Changes to
control system settings since should prevent a recurrence.
At Crownhill works (near Plymouth), South West Water linked a turbidity
value of >1NTU in May to the closure of the outlet valve on the 36” outlet
main of the treated water reservoir to facilitate drain down and cleaning
of this asset. The sample had been taken when the reservoir was not in
service, therefore it was not representative of water entering supply.
Companies need to ensure that sampling staff are informed about the
operational status of assets so that compliance samples are collected only
when it is appropriate to do so.
Coliform bacteria at service reservoirs
Testing for coliform bacteria gives reassurance that the quality of water
held at these strategic points in the distribution system is adequately
maintained. The national standard requires that at least 95% of no less
than 50 samples collected from each service reservoir throughout one year
are free from all coliform bacteria. In 2011, all service reservoirs (including
water towers) in the region met the standard.
Coliform failures reported by South West Water at Bodelv a and Blackhill
service reservoir and at Wessex Water’s Two Ash service reservoir are
discussed in the section on E.coli at works and service reservoirs.
In response to single coliform failures at Strete reservoir (December) and
Stanborough reservoir (November) , South West Water drained and
inspected these reservoirs. Nothing untoward was found , however,
following a coliform failure at Yawl service reservoir (near Lyme Re gis)
a flood test revealed the potential for ingress through roof hatches.
Similarly, at Bindown reservoir (near Looe) in September , ingress as a
consequence of roof ponding was identified as a risk requiring mitigation
by a spray-on roof membrane. The company approach has involved
keeping the reservoir out of service until all remedial works are complete.
The Inspectorate is pleased to note this evidence of a proactive service
reservoir risk management strategy by South W est Water.
Wessex Water also displayed a proactive risk management approach to
reservoir maintenance in 2011. During September , a sample taken by
Wessex Water at Charlton Horethorne service reservoir (near Wincanton)
failed for coliforms. A range of issues were found at the site: inadequat e
sample facilities, low turnover and chlorine residual concentrations.
Abandonment of this site was previously planned for January 2012 and
this action was completed in February 2012. A coliform failure at Cockey
Down service reservoir (near Salisbury) i n September led to an internal
19

Dri nking water 20 11
inspection in late October. No integrity issues were revealed. The sample
line, tap and kiosk have been replaced.
During 2011, Bristol Water reported coliform failures at the following
reservoirs: Hutton (near Weston-Super-Mare), Tetbury, Tolldown (near
Gloucester) and Marshfield (near Bath). The Inspectorate has noted the
rise in coliform failures from one in 2010 to four in 2011 and further noted
that no cause was found in any of the five investigations. The Inspectorate
will be closely scrutinising the effectiveness of Bristol Water’s service
reservoir maintenance strategy.
The Inspectorate has noted that coliform bacteria were found in 20
(4 BRL, 6 SWT, 10 WSX) samples from service reservoirs in the Western
region during the year and this information will be taken into account in
planning the Inspectorate’s risk-based forward programme of technical
audit.
E.coli and Enterococci at consumers’ taps
A total of 12,582 consumers’ taps were tested in 2011 for E.coli and six
were positive (1 BRL, 3 SBW, 1 SWT, 1 WSX). Like E.coli, the presence
of Enterococci is indicative of faecal contamination and neither bacterium
should be found in any sample. In 2011, Enterococci were not detected
in any of the 1,466 samples collected acr oss the Western region from
consumers’ taps. There was no indication, from information gathered by
the four water companies, of a faecal contamination event affecting other
properties in these zones.
Samples from three properties in the Alderney North zon e contained E.coli
(May, November and December). Sembcorp Bournemouth Water carried
out fittings inspections and found irregularities in each case. These
included a redundant length of pipework under the sink, a connection to
a boiler filling loop, unhygienic anti-splash devices, lack of a non-return
valve fitted to a washing machine (allowing foul water to come back up
through the plug hole and into the sink) and an inoperable non -return valve
on a hose attached to an outside tap. Despite the company’s ef fective use
of fittings inspections to identify plumbing and backflow risks, the
Inspectorate has a concern about the pattern of relatively frequent E.coli
failures in this zone given the history of problems at the upstream works
(see the E.coli at works section).
A sample collected from a consumer’s tap in Wessex Water’s Allington
zone in November contained E.coli and coliforms. Sequential follow-up
water samples and a fittings inspection all yielded satisfactory results ,
in contrast to the findings of Br istol W ater in relation to a property in the
Filton and Northville zone in September where E.coli and coliforms were
20

W estern re gion
detected. In this case, re-samples on two separate occasions were positive
before and after the tap was cleaned. The tap was loose fitting and
unhygienic, and a fittings inspection found an unapproved hose connection
at the property. Consumers were advised to boil water . South West Water
issued a notice for corrective action by a property owner following
identification of fittings irregularit ies when investigating an E.coli and
coliform failure in Restormel Central zone during November. The
Inspectorate is pleased to note the involvement of fittings inspectors in the
investigation of water quality failures by companies in the Western region.
Chemical quality
The drinking water regulations set out the minimum testing requirements
for all chemical and physical parameters. A full summary of the results
of testing by each company, including the results for indicator parameters ,
is provided on the Inspectorate’s website and on the CD accompanying
this report.
The following text and Table 8 set out the results for those parameters
where there has been a failure to meet a European or national standard
(mandatory quality standards) and any other para meter of interest. In
addition, at the request of local authorities, the results of testing for
fluoride, iron, lead, manganese, nitrate, nitrite, pesticides and radioactivity
are given. New this year, the Inspectorate has also included instances
where residual chlorine results were reported at a level above that
considered desirable on grounds of consumer acceptability (2mg/l).
21

Dri nking water 20 11
Table 8: Chemical and physical parameters
The number of tests performed and the number of tests not meeting
the standard or screening value
Parameter
Aesthetic parameters
Current
standard or
specified
concentration 1
Total
number
of tests
Number of
tests not
meeting
the
standard 4
Additional information
– odour
4,126 5 SWT (1), WSX (4)
No abnormal
change
BRL (1), SWT (1),
– taste 4,098 7
WSX (5)
Aluminium 200μg/l 4,542 1 BRL (1)
Chlorine – residual (free) 2 2mg/l 75,251 2 BRL (1), SWT (1)
Chlorine – residual (total) 2 2mg/l 75,797 11 BRL (3), SWT (8)
Fluoride 1.5mg/l 1,186 0
Iron 200μg/l 4,275 22
Lead (current standard) 25μg/l 1,476 2 WSX (2)
Lead (future standard) 10μg/l 1,476 12
Manganese 50μg/l 4,272 3
Nickel 20μg/l 1,473 1 BRL (1)
Nitrate 50mg/l 1,794 0
Nitrite 0.5mg/l 1,796 0
Pesticides – total 0.5μg/l 1,367 0
Pesticide – individual 3 0.1μg/l 39,821 2
pH (Hydrogen ion) 6.5 – 9.5 5,117 5
Radioactivity
Gross alpha 0.1Bq/l 688 2 SWT (2)
Gross beta 1.0Bq/l 688 0
Tritium 100Bq/l 111 0
BRL (16), SBW (2),
SWT (1), WSX (3)
BRL (6), SWT (1),
WSX (5)
BRL (1), SWT (1),
WSX (1)
MCPP (Mecoprop)
SWT (2)
BRL (1), SWT (2),
WSX (2)
Turbidity (at consumers’
taps)
4NTU 5,056 1 BRL (1)
Notes:
1 For comparison, 1mg/l is one part in a million, 1μg/l is one part in a thousand million.
2 The value of 2mg/l is a consumer acceptability value set by the Inspectorate.
3 A further 3,925 tests were done for aldrin, dieldrin, heptachlor, heptachlor epoxide, all of which met the
relevant standard.
4 Standard or screening value.
22

W estern re gion
Aesthetic parameters
Consumers expect their drinking water to be clear and bright in
appearance and free from discer nible taste or odour. In recognition of this
the regulations stipulate national standards for colour, odour and taste.
Companies are required to investigate the cause of any adverse consumer
taste or odour report and sample failures for aesthetic parameter s. Where,
through investigation, the company established the cause to be
arrangements or conditions within premises , these are described in the
Maintaining water quality at the tap section.
In the Western region overall, there were seven samples that faile d to
meet standards for taste (1 BRL, 1 SWT, 5 WSX) out of a total of 4,098
tests. In relation to these seven samples, five also failed for odour
(1 SWT, 4 WSX). There were no failures of the colour standard. Most of
the taste and odour failures recorded by Wessex Water are described in
the section Chemical quality – Geosmin and the remainder are described
below or in the Maintaining water quality at the tap section.
Sweet
This descriptor usually relates to samples where tap water is artificially
softened within premises. However, South West Water did not identify
a water softener or any other plumbing irregularities when carrying out
a fittings inspection in response to a sample exhibiting a sweet taste and
odour collected in September from a consumer’ s tap in the Prewely North
zone. The Inspectorate expects companies to carry out enhanced
monitoring in zones where unexplained taste or odour failures are
recorded.
Aluminium
Aluminium can occur naturally in some water sources. Also, aluminium -
based water treatment chemicals may be used at surface water works
to aid the process of filtration.
In 2011, a total of 4,542 samples were tested for aluminium in the Western
region. Cholderton and District Water, Semcorp Bournemouth Water, South
West Water, Wessex Water, Veolia Water Projects Ltd and SSE Water
achieved 100% compliance with the aluminium standard. Just one test
exceeded the standard, in a sample collected in the Bristol Water’s
Fishponds and Mangotsfield zone, and this was found not to be related
to process control at the works.
A level of 345ug/l of aluminium was recorded in a sample collected from
a consumer’s tap in August, in the Fishponds and Mangotsfield zone on
the outskirts of Bristol, operated by Bristol Water. The same sample also
23

Dri nking water 20 11
failed the standards for iron and manganese. The company identified a
length of cast iron pipework at the end of the main in an area of low water
flow. After flushing to remove deposits, further tests gave satisfactory
results. The zone is subject to a legally binding program of mains
rehabilitation and replacement, which is due for completion in March 2015 .
The Inspectorate expects investigations of failures to be taken into
account during the planning of this distribution maintenance work.
Chlorine
Chlorine is widely used in households as bleach. It is an important
disinfectant with many applications in the home and workplace wherever
the maintenance of good hygiene is necessary. It is the most common
oxidative disinfectant used in swimming pools and there is a long history
of its use in water supplies stretching back for a century. Typical levels
of residual chlorine in public water supplies in the UK are in the range
of 0.1 – 1.0mg/l, well below levels typically found in many other parts
of the world. Human exposure to chlorine in drinking water has not been
associated with any specific adverse health effects and the W orld Health
Organisation’s (W HO) health-related guideline value for chlorine is set
at 5mg/l.
There is not a numerical standard for resid ual chlorine in drinking water
in England, however, water companies are required to measure residual
chlorine whenever they are collecting samples for microbiological analysis
and any abnormal change in chlorine concentration must be investigated.
In addition, water companies are expected to have regard to consumer
acceptability by investigating chlorine -related taste and odour complaints
from consumers. The Inspectorate has set a screening value of 2mg/l for
the purpose of assessing the effectiveness of r esidual chlorine
management by water companies.
In October, South West Water recorded a total chlorin e level of 2.89mg/l
when collecting a consumer tap sample in the Prewley North zone. The
sampler discussed the on-site measurement with the customer who
explained that the tap had been bleached prior to the sampler attending
the property. The sampler spoke to his supervisor, flushed the tap and
noted that a subsequent chlorine measurement was lower. He then carried
out checks at a neighbour’s property and th e local service reservoir
confirming there was not a problem with the wider supply.
During September, at Drift works, South West Water recorded two high
chlorine values (2.67 and 2.73mg/l). The company had previously
increased the chlorine dose at the work s for a fortnight due to algal growth
and elevated ammonia in the raw water. This action had resulted in higher
than normal chlorine levels at a number of service reservoirs: Cryor, Ding
24

W estern re gion
Dong, Kerris (Chywoone), and Leha. During this same period there were
25 consumer contacts about abnormal taste and odour. The company has
since reviewed the operation of the works during periods when the
characteristics of the raw water require action to optimise water treatment.
The Inspectorate expects the company to upd ate its regulatory risk
assessment documenting the learning in relation to both the risk and the
control measures.
During 2011, Bristol Water recorded three high chlorine values at Littleton
works. The first of these was a total chlorine residual of 2.02mg/l in June
and in October values of 2.09mg/l free chlorine and 2.25mg/l total chlorine
were recorded. Ozone is the primary disinfectant at this site and at the
time there was a known problem with the operation of the residual chlorine
dosing pumps. The company plans to move the dosing point to prevent
excess chlorine being dosed and to achieve a more stable residual
chlorine concentration. The Inspectorate expects the company to update
its risk assessment to reflect this risk and both the short and long -term
mitigation measures.
Disinfection by-products
To ensure the microbiological safety of public water supplies , water
companies are required to disinfect water at the treatment works before
supplying it through the distribution system to consumers. Disinf ection
may be achieved by any appropriate physical or chemical method, or
a combination of the two. The choice of method will depend on a range
of site-specific factors, but an important consideration is the requirement
to keep disinfection by-products (DBPs) to a minimum. This 1998 EU
Drinking Water Directive requirement was introduced formally into national
law in January 2010.
Chemical disinfectants are powerful oxidants that react with organic and
inorganic matter in raw water to form other compounds known as DBPs.
There are many different DBPs and the likelihood of any particular ones
occurring in a given water supply can be predicted from the raw water
quality and the method of disinfection. A summary of commonly
encountered DBPs can be found in the WHO’s Guidelines for Drinking
Water Quality 2004 Section 8.5.4. Based on current global research it is
felt that two groups of compounds, trihalomethanes (THMs) and
haloaceticacids (HAAs), serve as adequate indicators for monitoring DBP
performance overall. The most appropriate means of controlling DBPs is
to remove organic precursors from the raw water before it is disinfected.
The Inspectorate has made a preliminary assessment of how well
companies in the Western region are meeting the DBP rule using water
company THM data reported for 2011. For this initial evaluation, the
25

Dri nking water 20 11
Inspectorate has set a screening criterion of an an nual average value
of 50µg/l
Company
Number of
zones operated
by company
Number of zones
exhibiting an annual
average for
trihalomethanes
>50µg/l
Bristol W ater 52 0 -
Cholderton and
District W ater
1 0 -
Name of zones
exhibiting an
annual average
for
trihalomethanes
>50µg/l
Sembcorp
Bournemouth W ater
10 0 -
South W est W ater 32 12
Drift
W endron
College
Tamar
Stithians
Northcombe
Prewley North
Restormel W est
Prewley W est
Burrows
Littlehempston,
Tottiford and
Bovey Cross
Venford
SSE W ater 11 0 -
Veolia W ater
Projects Ltd
1 0 -
W essex W ater 91 0 -
Industry total 1,670 37 -
Note: Figures are for whole company areas .
Fluoride
Traces of fluoride occur naturally in many water sources, particularly in
groundwater. For example, fluoride occurs in water drawn from the great
Oolite limestone in the area of North East Somerset and West Wiltshire
26

W estern re gion
(particularly around Lacock). Consumers can obtain specific information
on the level of fluoride in the drinking water supply to their home or
workplace from their water company.
Fluoride is not removed by conventional water treatment. Some companies
fluoridate water supplies when required to do so by the local public health
authority as a protection against tooth decay. There are no fluoridation
schemes in the Western region. In 2011, all 1,186 tests for fluoride taken
across the region met the regulatory standard (1.5mg/l). Please refer to
the Inspectorate’s website (www.dwi.gov.uk) for more information on
fluoridation.
On 11 February 2011, the judicial review brought against South Central
Strategic Health Authority (SCSHA) by Geraldine Milner was concluded.
The review was about whether the SCSHA followed the correct procedure
when deciding to fluoridate the Southampton and South W est Hampshire
area. The judge found in favour of the SCSHA and technical feasibility
of the fluoridation arrangements are being finalised. No new fluoridation
schemes were proposed in the Western region in 2011.
Geosmin
Geosmin is a natural substance produced by the seasonal growth of algae
in slow moving surface water. It gives rise to a characteristic ‘earthy’ or
‘musty’ taste and odour discern ible to consumers.
In March/April and September/October , Wessex Water reported an
earthy/musty taste and odour in nine cons umer tap samples (four odour,
five taste) collected from Porlock zone near Minehead. The company had
identified, through risk assessment, that the treatment at Porlock works
was unable to cope adequately with the seasonal occurrences of geosmin
in Nutscale raw water reservoir. Changes in catchment management, which
have seen a return of the moorland to its natural state (in Exmoor National
Park) has resulted in different run off patterns and nutrient levels in
surface water. This has necessitated a more co mplex and sophisticated
water supply management regime, whereby the works has to be taken out
of supply and the area rezoned when raw water quality cannot be treated
adequately. The raw water main between Nutscale reservoir and Porlock
works is flushed and sampled twice weekly, and the works is only returned
to supply following satisfactory samples. The Inspectorate expects the
company to validate the control measure (water supply management
regime) as being sufficiently robust to prevent taste and odour fa ilures
at consumers’ taps at all times. If seasonal taste and odour events
continue, then the risk assessment should be updated and the need for
alternate control measures, such as additional treatment, identified.
27

Dri nking water 20 11
When consumers experience a persistent t aste or odour, they may contact
their water company to report the problem. Records of these contacts in
each zone are recorded by water companies and passed to the
Inspectorate annually. Figure 10 shows the contact rate per thousand
people across the Western region and the location of the taste or odour.
Figure 10: Rate of taste and odour contacts per 1,000 population
Figure 10 illustrates the location of taste and odour failures that were not
attributed to premises and shows the background level of cons umer
contacts reporting taste and odour problems. It can be seen that the
highest rate of consumer contacts occurred in three zones ; Broadwood
Direct zone adjacent to Porlock zone where sample failures were reported
in 2011, Chute zone near Andover and Castleton zone (Sherborne). The
Inspectorate expects companies to use mapping of consumer contacts as
part of the process of risk assessment and risk management.
Nitrate and nitrite
Nitrate occurs naturally in all source waters due to the decay of vegetable
material in soil. Nitrogenous fertilisers used on arable farmland are a
significant source of nitrate in groundwater. Rainfall washes nitrate from
the soil into lakes, rivers and streams. Nitrate levels can be reduced by
water treatment or by blending wit h another low nitrate water source.
In 2011, all 1,794 tests for nitrate met the standard (50mg/l).
28

W estern re gion
From extensive information gathered by the water companies, a likelihood
of drinking water supplies in the region failing the nitrate standard in the
longer term has been confirmed at some sites. As a consequence, a legally
binding agreement is in place for catchment management and the
construction of an integrated grid system to facilitate blending, if required,
at several W essex Water sites: Bulbridge, Ch irton, Dunkerton, Fonthill
Bishop, Hooke, Sturminster and W ylye which will benefit approximately
22,000 consumers. The catchment management measures are due to be
delivered by 2015 with the grid system in place by March 2018. Similarly,
a blending scheme is to be progressed at Bristol W ater’s Frome works in
Somerset by the end of September 2014.
Nitrite may be formed when chloramine is used as the residual disinfectant
to maintain the microbiological quality in the distribution network. The
formation of nitrite is controlled by careful optimisation of the
chloramination process. Sembcorp Bournemouth W ater uses chloramine as
the residual at all its treatment works. Nitrite can also form in samples of
water, after collection and before analysis, especially if the sample is not
kept cool.
In 2011, all 1,796 tests carried out across the region for nitrite met the
standard.
Pesticides and related products
This group of substances, generically called pesticides, includes many
organic chemicals ranging from wee d killers, to insecticides and
fungicides. Water sources may contain traces of pesticide residues as a
result of agricultural use (pest control on crops) and non -agricultural use
(herbicides for weed control on highways, railways etc.). Water companies
are required to assess the risk to drinking water supplies of pesticide use
in source water catchments and then test for those that might be present.
Companies have documented potential and actual pesticide hazards
through their risk assessments as informed b y raw water monitoring. When
pesticides are first detected, water companies will enhance the monitoring
of raw water and notify the Environment Agency to facilitate appropriate
action in the catchment to safeguard drinking water quality.
In 2011, none of the tests in the region exceeded the standard for total
pesticides. Likewise, there was 100% compliance (1,367 tests) for the four
pesticides with a standard of 0.03μg/l. Out of a total of 39,821 tests for
those individual pesticides with a standard of 0.1 μg/l just two exceeded
the standard. The circumstances and substances involved are summarised
below.
29

Dri nking water 20 11
Mecoprop (MCPP)
Mecoprop is a herbicide frequently found with other herbicides such as
2,4-D or dicamba. Its predominant use is for weed control in lawns ,
amenity agriculture and cereals. The standard is 0.1μg/l.
In December, Mecoprop was detected at a level of 0.482μg/l in a sample
from Wendron works (near Helston in Cornwall). A follow-up sample also
contained mecoprop at a level above the standard, but lower than seen in
the original sample. South West Water increased the dose of powdered
activated carbon (PAC) and implemented a strategic flushing programme
to remove mecoprop from the distribution system. The Environment Agency
were notified and visited farms within the catchment area, but failed to
identify a point source. The company has since updated its risk
assessment.
pH (Hydrogen ion)
The acidity of water is measured by pH. The standard for pH requires it to
be above 6.5 and below 9.5. The most frequent problems arise in upland
areas where water may pick up iron and humic acids from peaty soil,
resulting in acidic raw water (low pH), which is commonly described as
‘soft water’. Such water has an increased potential to corrode iron pipes.
Where pH values above 9.5 occur this is usually due to leaching from
cement mortar-lined mains.
In the Western region, out of a total of 5,117 tests, the standard was
exceeded on five occasions in 2011 (1 BRL, 2 SWT, 2 WSX).
In January, Wessex Water reported a pH value of 6.4 in a sample from
a concessionary raw water supply at two farms in the Nutscale Valley,
Exmoor, where treatment is by ‘point of use’ devices. The company
investigation found that the raw water main from Porlock had been used
intermittently and pH in the raw water reservoir had dropped rapidly due
to heavy rainfall and significant snowmelt. Subsequent samples from all
properties using ‘point of use’ treatment devices were satisfactory. Since
the Point of Use water treatment units were replaced in 2006, there have
been no pH failures in relation to this supply, but following this event the
company will be reviewing its risk assessment.
During July, Bristol Water reported a pH of 6.28 from a consumer ’s tap
sample in Filton and Northville zone. Fur ther samples were satisfactory
ruling out a wider problem. From discussion with the customer the
company concluded that there was a water softener or other treatment
device installed at the property. The Inspectorate expects companies to
30

W estern re gion
carry out a fittings inspection when investigating unusual results from
a tap in a property.
South West Water recorded a pH of 9.6 in a consumer’s tap sample
collected from the Bastreet and St Cleer zone in March. The company
investigation attributed the cause to low flow in the asbestos cement-lined
main and this was dealt with by flushing. The company identified a similar
situation when investigating a pH value of 10.0 in the Lowermoor and
Delank zone in July, which was linked to low flow in cement -lined ductile
iron main and where the company plans to install a hydrant to facilitate
flushing of the local system. Cement -lined mains are a feature of the
distribution system in Cornwall and long -term remedial measures are being
addressed through the company’s Distribution Ope ration and Maintenance
Strategy. The Inspectorate expects the company to update regulatory risk
assessments to formally document when a flushing regime is introduced as
a short-term control measure.
Radioactivity
Gross alpha/gross beta/total indicative d ose
Radioactivity in raw water can originate from natural substances or from
a specific point emission. Water companies are required to screen for
radionuclides that emit either alpha or beta particles. If such screening
exceeds guide values (gross alpha 0.1Bq/l, gross beta 1.0Bq/l), then fuller
analysis for specific radionuclides is carried out to determine the origin.
Total indicative dose (TID) is a measure of the effective dose of radiation
through consumption of the water. The guide value is 0.1mSv/ye ar.
In 2011, out of 1,376 tests across the Western region there were two
detections of gross alpha and no detections of gross beta above screening
values (SWT).
Gross alpha at levels above the screening value was recorded in samples
collected from Wendron works (September and November) where
screening is carried out monthly. South West Water has calculated TID and
results were below the guide value. Naturally occurring radio nucleotides
(radium and uranium) are a feature of the Wendron catchment and testin g
for radon, radium and uranium has been carried out by South West Water .
To date all results have proved satisfactory.
Tritium
Monitoring for tritium is necessary only where a source of tritium is present
within the catchment and it cannot be shown on t he basis of other
surveillance programmes or investigations that the level of tritium is well
below its parametric indicator value of 100Bq/l.
31

Dri nking water 20 11
South West Water has established, by risk assessment, that monitoring for
tritium is not required. All tritium testing by the other companies in the
Western region has given results well below 100Bq/l.
Maintaining water quality in distribution
Elevated levels of iron or manganese are objectionable to consumers
because the water may appear turbid or discoloured due to unsightly
deposits and may also stain laundry and water fittings. Since 2004 , the
Inspectorate has been monitoring the progress of companies ’ distribution
maintenance work using an index made up of three parameters (turbidity,
iron and manganese). Figure 11 shows the long-term improvements in the
Western region. In 2011, there was a deterioration largely due to mains
renovation and replacement in the region.
Figure 11: Percentage of tests meeting the standards for turbidity,
iron and manganese.
100.00
99.90
99.80
99.70
99.60
99.50
99.40
99.30
99.20
99.10
99.00
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Bristol Water
Sembcorp Bournemouth Water
South West Water Wessex Water
Note: SSE W ater only beg an sup plying water in 200 8 . They ha ve achieved 10 0 % in each yea r
s ince.
Veolia W ater Proj ects onl y beg an sup pl ying wat er to Tidworth in 20 09. They ha v e achieve d 100%
in each ye ar since.
Chol de rton an d District W ater ha v e achieved 100% in each yea r exc ept 200 2 (9 5 .83%), 20 03
(97. 62%) and 200 4 (97.22%).
Discolouration of tap water often prompts consumers to contact their water
company. The number of people contacting water companies about
32

W estern re gion
discoloured water are reported annually to the Inspe ctorate in accordance
with Information Letter 1/2006. Looking at the trend since 2007 it can be
seen from figure 12 that, across England and Wales, the numbers of
consumers contacting their water company to complain about discoloured
water has fallen from about 84,000 to below 54,000. In the Western region,
the downward trend is more pronounced than that for the industry overall
with the figure now standing at just below 11,000 , down by 45% since
2007. These consumer contacts represent one-fifth of all consumer
contacts to the industry regarding discolouration.
Figure 12: Consumer contacts to companies for discolouration
2007–2011
90,000
80,000
70,000
60,000
50,000
40,000
30,000
Western region
Rest of Industry
20,000
10,000
0
2007 2008 2009 2010 2011
Looking more closely at the Western region, mapping of the rate of
consumer contacts by zone shows the changing picture from 2007 to 2011.
Rates of consumer contacts to companies about discoloured water in 2007
(Figure 13) illustrates the situation before the delivery of AMP4
improvement work by companies. Figure 14 shows the comparable rate
at the end of 2011 after completion of the AMP4 investment.
These maps show the benefit of mains renovation work completed by
South West Water in south west Cornwall and also areas around Bodmin
Moor and Exeter, although in 2011 consumers were still experiencing
discolouration problems in East Devon. The improvement in the area
served by Bristol Water is less marked, with an increase in consumers
reporting discolouration in areas near W ells and Midsomer Norton
33

Dri nking water 20 11
Figure 13: Rate of consumer contact per 1,000 population reporting
black, brown or orange water in 2007
Figure 14: Rate of consumer contact per 1,000 population reporting
black, brown or orange water in 2011
34

W estern re gion
Across the Western region in 2011, out of a total of 8,547 tests for iron
and manganese, there were 22 failures for iron (16 BRL, 2 SBW, 1 SWT, 3
WSX) and 3 failures for manganese ( 1 BRL, 1 SWT, 1 WSX). In addition, there
was one failure of the turbidity standard of 4NTU (1 BRL) and no failures
of the polycyclic aromatic hydrocarbons ( PAH) standards. Most failures
were treated as isolated occurrences of disturbances of mains deposits
cleared by flushing. There were no failures of any of these standards in
the areas served by Cholderton W ater, Veolia Water Projects and SSE
Water.
In 2011, Bristol Water recorded 16 failures of the standard for iron and one
manganese failure, all in zones covered by a legally binding programme of
AMP5 work to replace, rehabilitate and clean mains by 2015 : Sherston
Marshfield Pucklechurch and W ick, Henleaze, Redland Cotham and
Kingsdown, Stapleton St George and Conham, Stoke Bishop Coombe
Dingle and Henbury, Eastville and Easton, Long Ashton Failands and
Abbots Leigh, Avonmouth and Shirehampton, Bishopsworth Dundry and
Stanton Drew. The manganese failure was in the Fishponds and
Mangotsfield zone. In response to most failures, Bristol Water carried
out only a limited investigation taking no action if the resample was
satisfactory.
In the Shirehampton area of Bristol, investigative samples exceeded the
iron standard. The property was connected to t he supply towards the end
of a three-inch cast iron main and the company carried out remedial
flushing. Flushing was also carried out in another part of Bristol
(Speedwell) when a sampling survey revealed that iron failures were more
widespread. This area is included within the legally binding programme of
work (Stapleton St. George and Conham zone) , however, the Inspectorate
has noted that the failure occurred in a public building therefore Bristol
Water is under a duty to inform the building owner of the cause of the
problem and the short- and long-term remedies. The Inspectorate
considers Bristol Water should be doing more in relation to short -term
control measures and customer communications in areas where the
company is not compliant with the iron stand ard and it is to be expected
that customers will continue to experience discoloured water until delivery
of longer-term improvements.
In 2011, Sembcorp Bournemouth W ater reported only two failures of the
iron standard, each in a different zone. The company investigation
identified that the sample in Alderney South zone had been collected from
a café which had just re-opened for business following closure over the
winter period. The main was flushed and further tests gave satisfactory
results. No cause was found for the other failure in a sample from a
consumer’s tap in a property in St Catherines zone. The Inspectorate
expects this information to be taken into account in Sembcorp
35

Dri nking water 20 11
Bournemouth Water’s regulatory risk assessments and their Distribution
Operation and Maintenance Strategy (DOMS).
South West Water reported single failures of the standards for iron and
manganese in 2011. The iron failure in the Drift zone occurred in a tap
sample collected from a holiday let property situated at the end of the
distribution system and flushing resolved the problem. The manganese
failure in the Prewley West zone was a similar isolated occurrence with
all re-samples being satisfactory.
In 2011, there were three iron failures and one failure of the manganese
standard in the area served by Wessex Water. Maundown North zone is
covered by a legally binding programme of work to renovate the
distribution system and a sample collected in May failed the standards for
both iron and manganese. The Inspectorate expects that this information
will be taken into account in the company’s risk assessment and DOMS.
Wessex Water linked an iron failure in a sample from the Odcombe zone
to a rezoning exercise to facilitate planned works. In the Dorchester zone,
the company identified a long length of iron pipework to the building, which
had not been used often during the Christmas and New Year period and
the samples, after flushing, were satisfactory.
Annex 4 details the legally binding programmes of distribution
maintenance work schedule d to be completed between now and 2015
to address distribution-related water quality problems in the region.
Maintaining water quality at the tap
Consumers expect their drinking water to be clear and bright in
appearance and free from discernible taste, odour or contaminants.
Several parameters are not routinely found in mains water , but instead
they gain access to tap water close to the point of use. For example,
certain plumbing metals (antimony, copper, lead and nickel) and sodium
introduced by water softeners installed in premises. Accordingly,
remediation of failures for these parameters requires action to be taken
by property owners.
36

Bristol Water
Cholderton and
District Water
Sembcorp
Bournemouth
Water
South West Water
SSE Water
Veolia Water
Projects Ltd
Wessex Water
W estern re gion
Table 15: Failures in samples collected from taps where the cause was
attributed to the premises
Parameter
Metals
Antimony 0–388 0–4 0–81 0–379 0–4 0–8 0–757
Copper 0–388 0–8 0–81 0–389 0–4 0–8 0–953
Lead >10 6–388 0–4 0–81 1–390 0–4 0–8 5–601
Nickel 1–388 0–6 0–81 0–389 0–4 0–8 0–597
Colour 0–1,277 0–4 0–403 0–1,545 0–4 0–12 0–1,563
Conductivity 0–1,408 0–4 0–411 0–2,130 0–12 0–12 0–1,870
Odour 0–1,280 0–2 0–402 0–1,540 0–4 0–12 0–886
pH 0–1,275 0–4 0–411 0–1,533 0–12 0–12 0–1,870
Sodium 0–388 0–12 0–100 0–379 0–4 0–8 0–1,212
Taste 1–1,279 0–2 0–400 0–1,522 0–4 0–12 0–879
Total 8–8,459 0–50 0–2,451 1–10,196 0–56 0–100 5–11,188
Note: Failures count ed in this table ar e those caused by con ditions or ar ran g em ents in the
prem ises .
Table 15 illustrates the distribution of failures for the parameters arising
within all types of premises across the region. Overall, across the Western
region in 2011, there were 13 failures of the standards for metals ( 7 BRL,
1 SWT, 5 WSX), and one positive detection for taste (1 BRL).
In all such cases, the company must advise consumers of the failure and
its cause with information about the actions needed t o safeguard health in
the short term, as well as what is needed to effec t a remedy in the longer
term. If the failure occurs in a public building, the company must go further
and, either alone, or acting in collaboration with the local authority,
enforce action by the relevant persons.
37

Dri nking water 20 11
Table 16 shows the number of investigations in public buildings resulting
from a failure of a standard or exceedance of an indicator parameter
value.
Table 16: Investigations in public buildings where action is required
by building owners
Company
Total tests at
consumers’ taps
Total tests
at public
buildings
Investigations in public
buildings
Bristol W ater 49,312 2,654 3
Cholderton
and District
W ater
Sembcorp
Bournemouth
W ater
South W est
W ater
370 0 0
17,851 109 1
74,139 2,780 3
SSE W ater 389 0 0
Veolia W ater
Projects Ltd
652 0 0
W essex W ater 68,116 2,935 0
Total 210,829 8,478 7
Lead
The most common source of lead in tap water is pipework installed before
the 1970s or the use of non-approved solder on cold water systems. Lead
may also leach from brass fittings. The standard of 10µg/l c omes into force
at the end of 2013, but the Inspectorate has strongly recommended that
companies take action ahead of the new standard coming into force
(Guidance on the Implementation of the Water Supply (Water Quality)
Regulations 2000 – Regulation 30).
In 2011, companies in the region identified 12 failures (6 BRL, 1 SWT,
5 WSX) of the future standard of 10µg/l out of a total of 1,476 tests,
a slight increase compared to the nine failures recorded in 2010.
As shown in figure 17, the situation regarding lead in the Western region
is now similar to that of the industry overall.
38

Percentage meeting standard
W estern re gion
Figure 17: Percentage of tests meeting the future standard of 10µg/l
for lead between 2001 and 2011
100
99
98
97
96
95
94
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
10ug/l Industry
10ug/l Regional
Most (9 out of 12) zones, where lead results greater than 10µg/l were
reported in 2011, receive phosphate dosing which results in a protective
layer inside pipework minimising the release of lead into tap water.
Two companies in the region, W essex Water and South West W ater, have
identified, in regulatory risk assessments, the likelihood of failing the
10µg/l lead standard and have put action plans in place. Wessex W ater
offers its consumers free replacement of lead service pipes (the part of the
pipe owned by the consumer) and is working closely with local authorities
and housing associations to identify properties where lead pipes can be
replaced. South West Water has implemented enhanced monitoring with
pipework identification to identify hot spot areas. The company is
investigating mechanisms available for discounting the cos t to customers
to encourage pipe replacement and is developing a lead awareness
communications campaign with local authorities.
In 2011, there was one occurrence in June of a failure of the 10µg/l lead
standard reported at a public building. On investigation, it was determined
that the property was a shop selling and repairing sewing machines. Such
premises are not classed as public buildings ( Information letter
10/2004). In light of this error the company has briefed staff on the
classification of public buildings. The supply pipe and customer side
pipework was replaced with medium-density polyethylene pipe in
December.
In 2011, the Inspectorate commissioned research with the water industry
research organisation (UKWIR) to look beyond the current water trea tment
measures now in place to reduce exposure to lead from tap water. The
study looked at a wide range of quantitative and qualitative data including
39

Dri nking water 20 11
the estimated number of properties with lead pipes in the UK, lead in tap
water measurements, and the costs and benefits of measures such as
water treatment and supply pipe and service pipe replacement. One output
of the project is an economic tool that enables users to estimate the costs
and benefits of baseline phosphate dosing alongside the alternatives of
lead pipe replacement or rehabilitation. Wider impacts were also
considered, including consequential wastewater treatment costs, carbon
emissions, health and other benefits , such as reductions in copper
concentrations in tap water.
The published UKWIR report, Alternatives to phosphate for
plumbosolvency control (12/DW/04/12), concluded there is no practical ,
alternative water treatment measure to the phosphate dosing regime
already in place and this was confirmed as being effective in reducing lead
concentrations in tap water substantially. The report also makes clear how
replacement of a water company supply pipe will not result in a significant
reduction in risk of exposure to lead unless the customer service pipe is
also replaced at the same time. The r esearch has identified additional
benefits attributable to phosphate dosing in the form of reduced amounts
of copper leaching from plumbing and a similar effect in relation to iron
concentrations. Pipe relining as an alternative to lead pipe replacement
is also discussed in the UKWIR report. Early testing of this approach did
not result in relining being widely applied by the industry, however, a new
relining method has been developed which is potentially more cost
beneficial and this is currently undergoi ng trials. The findings of this
research will be taken into account in water company strategies for
minimising exposure to lead in the long term.
Aesthetic parameters
Consumers expect their drinking water to be clear and bright in
appearance and free from discernible taste or odour. In recognition of this
the regulations stipulate national standards for colour, odour and taste.
Companies are required to investigate the cause of any failures for the
aesthetic parameters: taste, odour and colour.
In 2011, one sample collected by Bristol Water from a consumer’s tap in
the Clevedon zone in November exhibited a sweet taste that was
attributed, on investigation, to the installation of a water softener. There
was no separate mains fed drinking water tap and the h ouseholder was
given advice.
Wessex Water currently has two legally binding programmes of work to
improve taste and odour. One of these, at Blashford works, is delayed as
the works is being replaced with the Grid scheme and Blashford works will
40

W estern re gion
remain out of service, the other, at Sutton Bingham works is on target for
completion in 2014 when over 62,000 consumers will benefit from
improved water quality (see Annex 4).
During 2011, South West Water completed a programme of work to
improve taste and odour in the area served by Stithians works.
Drinking water quality events
Water quality events are classified into five broad categories based on the
initial company report. The categories are:
Not significant: no further information required by an inspector to assess
the event.
Minor: it is unlikely that further information would be required by an
inspector to assess the event.
Significant: a full company report is usually required to enable an
inspector to assess the event.
Serious: in addition to a full compa ny report, the assessment may involve
more than one inspector in the investigation.
Major: in addition to a full company report, will require an investigation led
by senior inspectors involving extensive information gathering and usually
site visits.
In 2011, companies in the W estern region notified the Inspectorate of
46 events. Table 18 shows how these events were classified.
Table 18: Water quality events in the region in 2011
Nature of event
Risk assessment category (DWI)
Minor/notsignificant
Significant Major/serious
2010 2011 2010 2011 2010 2011
Air in water - - - - - -
Chemical 3 3 1 1 - -
Discoloured water 3 5 5 4 - -
Inadequate treatment - - 1 - - -
Loss of supplies/poor pressure 7 5 1 2 - -
Microbiological 1 8 5 3 1 -
Taste/Odour - 6 - 2 - -
Health concern 1 - 1 - - -
Public concern 8 7 1 - - -
Other 2 - 1 - - -
Region overall 25 34 16 12 1 -
England and Wales 222 251 160 135 9 2
41

Dri nking water 20 11
A summary of the nature, cause and duration of each event categorised as
significant, serious or major, along with details of the Inspectorate findings
are set out in Annex 3. Most events were of relatively short duration and
the company took appropriate action to inform and safeguard consumers
and other stakeholders. A comparison of 2010 events with those of 2011
shows a decrease in the numbers of significant, serious and major events
in the Western region (12 compared to 17 in 2010).
Wider learning points from event assessments in the region in 2011 are
highlighted by the following cases:
Loss of supply and discolouration following planned work
In August, more than 3,000 consumers experienced discoloured water and
loss of supply when planned work by Bristol W ater went wrong. The work
to be carried out was the cleaning of a 24-inch main in the Long Ashton
area of North Somerset. This strategic main had been identified by the
company as the highest priority trunk main for renovation during the AMP5
period (2010–2015). To carry out the cleaning work, the company first
needed to change the supply arrangem ents by making a cross-connection
between another 600mm main at Barrow Treatment works and the 24 -inch
Long Ashton trunk main. This connection was to be made via a 500mm
main and to maintain supplies while making this connection, the company
had laid a short length of 180mm main with a pressure control valve
(PCV). A series of three valve operations was involved in making the
connection and the planning included a risk assessment, network
modelling and preparation of valve instructions. Shortly after the 18 0mm
connection had been made at the works, localised flooding was observed
on-site and consumers began to report no water. Part of the 24-inch main
had been abandoned in 2008 and the 180mm connection was to be made
at a point downstream of the valve separa ting the live and abandoned
section. However, because the Geographic Information System (GIS)
records were incorrect the connection was actually made into the
abandoned section resulting in no water entering the Long Ashton main.
Water instead flowed from the open ended section of the abandoned main
causing the localised flooding. The company were able to halt the planned
work and restore the system to its normal operation. However , the loss of
flow through the Long Ashton main mobilised deposits resulting in
discolouration of the downstream supply. The discolouration was
exacerbated by the automatic operation of a pumping station which
extended the area affected.
The Inspectorate was critical of the risk assessment for the planned work.
This did not cover the entire activity and used incorrect population
predictions (

W estern re gion
3,000) leading to the conclusion that the discolouration risk was minimal
when in fact the asset had already been identified as exhibi ting a high
discolouration risk. This event once again highlights for companies the
importance of verification of risk assessments and checks on the accuracy
of GIS records prior to commencement of planned work.
Unusual taste due to temporary loss of trea tment control
In August, 31 consumers living in the New Forest area of Hampshire
reported an unusual taste in their tap water (with up to 2 ,150 people
potentially affected). The supply to the area comes from Knapp Mill works
via Adlams works. After treatment at Knapp Mill, water with free residual
chlorine is transferred to Adlams works where the residual chorine is
converted to chloramine. Investigations carried out by Sembcorp
Bournemouth Water identified a chlorine control issue at Knapp Mill.
The online chlorine monitors were falsely reading zero causing the control
system to increase the dose to compensate. The works shutdown
automatically in response to the zero chlorine signal from the monitors,
however, when the pumps started at Adlams Lane, the bis ulphite dosing
at Knapp Mill was at a high level and , for a short period, water with a lower
than normal level of chlorine went forward to Adlams Lane. In
compensation, the system automatically increased the chlorine dose and,
as a consequence, water with a higher than expected level of chlorine left
Knapp Mill. Due to the slow reaction of the bisulphite dosing pumps at
Adlams works this chlorinated water went on to the next stage of treatment
(ammoniation) where the level of chlorine was further increased.
Essentially the works was operating in a manner contrary to its design,
causing changes to the characteristics of the water that were discernible
to consumers. The Inspectorate was critical of the design and
configuration of the chlorine control system (particularly its slow response
to changes in water quality). The company investigation was
unsatisfactory, especially in relation to the number, nature and timeliness
of samples from the distribution network. It is a breach of Regulation 10
not to carry out appropriate monitoring when there is reason to believe
water is not wholesome and compliance with Regulation 26 requires both
the design and continuous operation of water treatment to be fit for
purpose.
Unusual taste and odours following heavy rainfall
During October, 37 consumers in the Wadebridge, Bodmin and Padstow
areas of Cornwall contacted South West Water reporting an unusual earthy
taste and odour in tap water. After an increase in taste and odour
consumer contacts over two days the company beg an to dose powdered
43

Dri nking water 20 11
carbon at its Restormel works. Investigations confirmed an earthy taste
and odour in samples from consumers’ taps and also at Restormel works.
There had been recent heavy rainfall and this followed on from a
prolonged summer dry spell. Methyl-isoborneol (MIB) and geosmin, two
naturally occurring taste and odour causing compounds , were present at
levels only marginally above the taste threshold for the se compounds, but
the sensitivity of consumers was verified by the quick reporting of the
problem to the company. Advice to consumers was provided by the
company’s call centre and website, and South W est Water liaised with
local health professionals to maintain public confidence regarding there
being no potential impact on health. The Inspect orate was pleased to note
the proactive handling of this event. The company enhanced treatment
following the first consumer contacts working quickly to identify the root
cause and providing consumers with information. Companies are reminded
of the importance of developing skills and resources in event recognition
through rapid diagnosis of consumer water quality contacts.
During 2011, Wessex Water was cautioned for the misconnection of a
property to a sewer in 2010. The company admitted the offence of
supplying water unfit for human consumption and was formally cautioned.
No offences are currently under consideration by the Inspectorate in
connection with any of the events that occurred in the Western region
during 2011.
Technical audit activity
The Inspectorate has operated a risk -based approach to technical audit
since 2005 and no technical audit takes place without a reason.
On 14 December 2011, and in line with the Government’s Better
Regulation policy, Parliament gave the Chief Inspector powers in th e
Public Bodies Bill to recover the costs of its regulatory activities from the
industry from January 2013 onwards. During 2012, the Inspectorate has
consulted the industry and other stakeholders on the proposed charging
regime, the detail of which will be set out in Orders laid under the Bill in
autumn 2012. W hereas the work of inspectors in assessing companies’
compliance with the drinking water monitoring requirements as set out in
the drinking water regulations can be predetermined, the technical audit
activities of inspectors is less predictable, however, the nature and volume
of technical audit activity over the past s even years is illustrated in Figure
19 as an indication of the scope and extent of the new charging
arrangements going forward.
44

Number of audits
W estern re gion
Figure 19: Audit activity in the region 2005–2011
35
30
Abstraction and treatment
25
Service reservoir integrity and
management
Distribution operational maintenance
20
Sampling and analysis
15
Response to recommendations
10
Compliance with requirements for
Legal Instruments
Other
5
Consumer complaint handling
0
2005 2006 2007 2008 2009 2010 2011
Table 20 sets out all the risk-based technical audits, which took place in
the Western region during 2011 together with summary findings. This is
followed by information about industry wide themes assessed duri ng the
year and the particulars of consumer complaint investigations by
Inspectors, including a case study.
Table 20: Summary of the technical audit findings in the Western
region in 2011
Location and
Company
Main findings from audit
reason
Audit focus: Abstraction and treatment
South W est
W ater
Crownhill
works depot –
water supply
hygiene
Unsatisfactory.
Uncapped pipes and uncapped fittings ,
evidence of some used/dirty fittings in stores
available for reuse.
45

Dri nking water 20 11
Location and
Company
Main findings from audit
reason
W essex Rodbourne Generally satisfactory.
W ater works –
Critical of inadequate arrangements for the
microbiological chlorination, but noted plan to upgrade the
and turbidity disinfection s ystem .
failures
Recommended all monitors have visible
calibration status .
Noted two boreholes overflowing due to
malfunctioning air valves on top of the
headplates, raw water sample taps in poor
condition with a heavy layer of scale, lack of
sample point on supply to Rodbourne tower
despite this supply being capable of
independent use to supply Allington service
reservoir.
Audit focus: service reservoir integrity and management
W essex Hardenhuish Generally satisfactory.
W ater service
Noted inadequate drainage at sample
reservoir –
facilities, subsidence of reservoir banks,
microbiological mature tree growth on the banks, fencing
failures
around reservoir No.1 in poor condition.
Audit focus: Distribution operational maintenance
South W est Hole in the Unsatisfactory.
W ater ground – water Critical that contractors used dirty pipes and
supply hygiene fittings and could not make chloros up onsite
as the gangs did not carry Instachlor chlorine
tablets.
W essex
W ater
Depot and
hole in the
ground – water
supply hygiene
Mains relining,
Bridgwater –
procedures
Satisfactory.
Good practices observed in the field and the
depot was tidy and well managed.
W essex
Satisfactory.
W ater
W orking practices and procedures adhered to
in accordance with the Operational
Requirements and Code of Practice for the in -
situ Resin Lining of W ater Mains.
Audit focus: consumer complaint handling
South W est
All satisfactory.
W ater
Taste and
odour (1)
Other (1)
Discolouration
(1)
Audit focus: Compliance with requirements for Legal Instruments
South W est
W ater
Closure of
legal
Instruments –
general
Company was advised that insuffici ent
information was being provided to the
Inspectorate for sign off of Legal Instruments;
requirements explained and company has
since complied.
46

W estern re gion
During 2011, the Inspectorate audited the water supply hygiene
procedures of 11 companies across England and W ales following receipt of
information which increased the Inspectorate’s overall assessment of risk
associated with the way companies carried out work in their distribution
systems. These audits covered equipment storage conditions in depots
and vans, as well as mains repairs and meter installations. The outcome of
a majority of the audits were generally satisfactory, but examples of poor
practice were identified where contamination of drinking water might have,
or did, occur as a consequence of unsuitabl e storage of fittings, pipes and
other materials, insufficient clearance of soil from around open pipes
or connections, inadequate flushing or disinfection and a lack of good
hygiene within vans. The findings were summarised and published in an
Information Letter (IL 04/2012) to promote industry-wide learning and
improvement in this critically important aspect of day -to-day operations.
Figure 21: An example of unsuitable storage of pipes prior to
installation
47

Dri nking water 20 11
Complaints to the Inspectorate
The number of consumers who had cause to complain to the Inspectorate
because the company failed to resolve a water quality concern has fallen
from six in 2010 to three in 2011. Consumers also contact water
companies when they are dissatisfied with their water quali ty and
complaints regarding appearance, taste and odour and incidence of illness
has remained static between 2010 and 2011 at just below 18,000. By far
the largest component of these figures are the contacts for appearance
and 2011 has seen a levelling out of the previous encouraging reduction
in these contacts.
Table 22 shows the number of complaints about water quality received by
the Inspectorate in 2011 alongside the annual rate of consumer contacts to
water companies about water quality issues. Genera lly, complaints made
directly to the Inspectorate arise when a company’s handling of a
consumer contact has fallen short of best practice and this only comes to
light as a result of intervention by an inspector. For this reason, there is
no direct relationship between the figures set out in Table 22 and it is not
uncommon for complaints to the Inspectorate to be from customers of
companies exhibiting a low rate of consumer contact generally.
Table 22: Complaint rates to industry and to the Inspectorate
Company
Rate of consumer contacts
per 1,000 people 1 to water
companies in 2011
Number of complaints
received by the
Inspectorate in 2011
Bristol W ater 2.2 -
Cholderton and
District W ater
Sembcorp
Bournemouth
W ater
South W est
W ater
- -
1.1 -
6.9 3
SSE W ater 0.4 -
Veolia W ater
Projects Ltd
0.5 -
W essex W ater 2.4 -
Industry rate 1.9 34
1 Rat e of contacts for app e ara nce, taste an d odou r and illness .
48

W estern re gion
During 2011, the following complaint case illustrate s why the Inspectorate
considers it important that companies have in place effective arrangements
for diagnosing consumer contacts.
Case example
In April, a consumer contacted Ofwat to report tap water in Truro, Cornwall
with an unusually strong chlorine taste and odour and occasional
discolouration. The consumer who was referred correctly by Ofwat to the
Inspectorate, was aware of past work by South West Water replacing water
mains in the area in 2003 and this knowledge in part prompted the
complaint. The property in question was a holiday home. The consumer
was not a permanent resident and personal occupation of the property was
for only a few months each year. On being told of the complaint by the
Inspectorate, South West Water contacted the consumer and arranged to
meet with them when they were next in res idence. A water quality report
for the zone was provided. W hen the visit to the property took place the
company offered a fittings inspection and gave advice on backflow
prevention. Free check valves to fit to white goods were provided after
explaining how these can often be the cause of unusual tastes and odours.
By meeting with the consumer personally and by giving useful and
accurate information South West Water successfully reassured the
consumer.
Published research has shown how gaps in knowledge resu lt in heuristic
judgements whereby a person falls back on unrelated information from the
past (in this case mains renovation) to make sense of a current situation
thereby creating misperceptions and distrust, triggering complaining
behaviour (in this case the call to Ofwat rather than the water company).
The Inspectorate expects companies to invest in providing factual
information about water quality proactively to consumers recognising how
water quality contacts, when well handled, are the most effective w ay of
positively influencing consumer perceptions of drinking water quality .
For further information on the Water Supply (Water Quality) Regulations
2000, or the microbiological and chemical parameters covered by the
regulations please refer to the DWI website (www.dwi.gov.uk).
If you have a need for more specific information than that on our website,
please contact us on the DWI enquiry line: 0300 068 6400.
49

Dri nking water 20 11
Annex 1
Further sources of information
The publication Drinking water 2011 comprises the regional reports for
England and a report covering Wales. There are f our regional reports for
England (Central and Eastern, London and South East, Northern, and
Western) and one for Wales (in two languages). Each report presents
information from 2011 under the f ollowing headings:
Overview of drinking water quality in the region.
Water supply arrangements.
Drinking water quality testing.
Drinking water quality results.
Technical audit activity.
Drinking water quality events.
There are also separate reports covering private water supplies, one
covering England and one covering Wales.
The reports and other content are published on the DWI website
(www.dwi.gov.uk).
Content of the CD
The CD supplied with the printed report holds all of the above content and
additionally it contains:
Water company look-up tables
These summarise all the results of water company monitoring in 2011.
They provide information on:
what was tested;
how many tests were performed;
the range of the results of testing; and
how many tests failed to meet the standards.
Significant drinking water quality events in England and
Wales 2011
To promote shared learning, the Inspectorate has compiled a list of all
events that occurred in 2011 which illustrate the nature and cause of each
event, the main actions by the company and findings from the inspectors’
assessments. Relevant content from this overall list is contained in an
annex to each regional report.
50

W estern re gion
Annex 2
Glossary and description of standards
These definitions will assist the underst anding of the report where
technical terms have been used.
µg/l
1,2-Dichloroethane
Acrylamide
Aesthetic
Aggressive
Alkali
Aluminium
Ammonium
microgram per litre (one millionth of a gram
per litre).
is a solvent that may be found in groundwater in
the vicinity of industrial sites. W here necessary
it can be removed by special water treatment.
A European health-based standard of
3μg/l applies.
European health-based standard. A monomer
is not normally found in drinking water. It is
produced in the manufacture of polyacrylamides
occasionally used in water treatment.
Its presence in drinking water is limited by
control of the product specification. Standard
is 0.1µg/l.
associated with the senses of taste, smell
and sight.
a term used to indicate that the water has a
tendenc y to dissolve copper (and other metals)
from the inner surface of a pipe or water fitting
such as a tap.
a solution containing an excess of free hydroxyl
ions, with a pH greater than seven.
occurs naturally in some source water s. It is
removed from drinking water by conventional
water treatment (coagulation and filtration).
Aluminium sulphate and polyaluminium chloride
may be used as water treatment chemicals at
some water treatment works. A national standard
of 200μg/l applies.
salts are naturally present in trace amounts in
most waters. Their presence might indicate
contamination of sanitary significance and they
interfere with the operation of the disinfection
process. An indicator parameter with a guide
value of 0.5mg/l.
51

Dri nking water 20 11
Analytical quality control
(AQC)
Antimony
Aquifer
Arsenic
Authorised departure
Benzene
Benzo(a)pyrene
Boron
Bromate
the method used to ensure that laboratory
analysis methods are performing correctly.
is rarely found in drinking water.
Trace amounts can be derived from brass tap
fittings and solders. A European heal th-based
standard of 5μg/l applies.
water-containing underground strata.
occurs naturally in only a few sources of
groundwater. Specific water treatment is required
to remove it. A European health-based standard
of 10μg/l applies.
authorisation for a water company to temporarily
supply water exceeding a drinking water
standard, granted by the authorities only when
there is no risk to human health.
is present in petrol. It is not found in drinking
water, but it can migrate through underground
plastic water pipes if petrol is spilt in the vicinity.
A European health-based standard of 1μg/l
applies. Some bottled waters and soft drinks
which include sodium benzoate as an ingredient
have been reported as containing benzene.
is one of several compounds known as polycyclic
aromatic hydrocarbons (PAHs). Their source in
drinking water is as a result of deterioration of
coal tar, which many years ago was used to line
water pipes. Due to extensive water mains
refurbishment and renewal it is now rare to
detect this substance in drinking water.
A European health-based standard of
0.01μg/l applies.
in surface water sources comes from industrial
discharges or from detergents in treated sewage
effluents. The very low concentrations found in
some drinking waters are not a concern to
public health. A European health-based standard
of 1mg/l applies.
can be formed during disinfection of drinking
water through a reaction between naturally
occurring bromide and strong oxidants (usually
ozone). It may be generated in the manufacture
of sodium hypochlorite disinfectant.
Exceptionally, groundwater can be contaminated
with bromate, released from industrial sites .
A European health-based standard of
10μg/l applies.
52

W estern re gion
Bulk supply
Cadmium
Catchment
Chloramination
Chloramine
Chloride
Chlorine residual
Chromium
Clostridium perfringens
Coagulation
Coliform bacteria
water supplied in bulk, usually in treated form,
from one water company to another.
is rarely detected in drinking water and trace
amounts are usually due to dissolution of
impurities from plumbing fittings. A Europea n
health-based standard of 5μg/l applies.
when used in connection with water, the
catchment is the area drained by a river or
water body.
the process of generating a chloramine
disinfectant residual in water leaving a
treatment works.
a substance formed by a reaction between
chlorine and ammonia, used as a disinfectant in
distribution s ystems because of its long -lasting
properties compared to chlorine.
is a component of common salt. It may occur in
water naturally, but it may also be present due
to local use of de-icing salt or saline intrusion.
An indicator parameter with a guide value
of 250mg/l.
the small amount of chlorine or chloramines
present in drinking water to maintain i ts quality
as it passes through the water company’s
network of pipes and household plumbing.
is not present in drinking water. A European
health-based standard of 50μg/l applies.
is a spore-forming bacterium that is pr esent in
the gut of warm -blooded animals. The spores can
survive disinfection. The presence of spores in
drinking water indicates historic contamination
that requires investigation. The standard is
0 per 100ml.
a process employed during drinking water
treatment to assist with the removal of
particulate matter.
are widely distributed in the environment often
as a result of human or animal activity, but some
grow on plant matter. Their presence in a water
supply indicates a need to investigate the
integrity of the water supply s ystem.
The standard is 0 per 100ml.
53

Dri nking water 20 11
Colony counts
Colour
Communication pipe
Compliance assessment
Compound
Concessionary supplies
Conductivity
Contact tank
Contravention
Copper
are general techniques for detecting a wide
range of bacteria, the types and numbers being
dependent on the conditions of the test.
These counts, if done regularly, can help to
inform water management, but they have no
direct health significance. The standard is ‘no
abnormal change’.
occurs naturally in upland water sources.
It is removed by conventional water treatment.
A national standard of 20mg/l on the
Platinum/Cobalt (Pt/Co) scale applies.
the connection from the water main to the
consumer’s property boundary.
a comparison made by the Inspectorate of data
gathered by water companies against standards
and other regulatory requirements.
a compound consists of two or more elements
in chemical combination.
historical free supplies of water for a
householder, established when a company
wanted to lay mains across land and the
landowner might agree, subject to a permission,
to take a supply of water from the main.
is a non-specific measure of the amount of
natural dissolved inorganic substances in
source waters. An indicator parameter with
a guide value of 2,500µS/cm.
a tank, normally situated on a treatment works
site, which forms part of the disinfection process.
A disinfectant chemical (normally chlorine) is
dosed into the water as it flows into the tank.
The period of time that the water takes to flow
through the tank allows sufficient ‘contact’ time
for the chemical to kill, or deactivate, any
viruses or pathogenic organisms that may be
present in the water.
a breach of a regulatory requirement.
in drinking water comes mostly from copper
pipes and fittings in households. In general,
water sources are not aggressive towards
copper, but problems very occasionally occur on
new housing estates. These ‘blue water’ events
can be avoided by good plumbing practices.
A European health-based standard of
2mg/l applies.
54

W estern re gion
Cryptosporidium
Cyanide
Dead leg
Distribution systems
Drinking water standards
is a parasite that causes severe gastroenteritis
and can survive disinfection. In the UK,
continuous monitoring is undertaken at works
classified by the company as being at
significant risk.
is not present in drinking water. A European
health-based standard of 50μg/l applies.
refers to a piece of piping which is stopped off at
one end, but is connected to the supply at the
other end and can result in stagnant water in
the pipework.
a water company’s network of mains, pipes,
pumping stations and service reservoirs through
which treated water is conveyed to consumers.
the prescribed concentrations or values listed
in regulations.
EC Drinking Water Directive Council Directive 98/83/EC December 1998 –
setting out drinking water standards to be
applied in member states.
Enforcement action the means, as set out in the W ater Act 1989
and consolidated into the W ater Industry Act
1991, by which the Secretary of State requires
a water company to comply with certain
regulatory requirements.
Enterococci
Environment Agency
Epichlorohydrin
Epidemiology
see Escherichia coli.
the Environment Agency is responsible for
maintaining or improving the quality of fresh,
marine, surface and underground water in
England and W ales.
can be found in trace amounts in polyamine
water treatment chemicals. Its presence in
drinking water is limited by control of the product
specification. A European health-based standard
of 0.1μg/l applies.
a process of studying the distribution of cases of
disease within a population in relation to
exposure to possible sources of the infection,
with a view to establishing the actual source of
the infection.
55

Dri nking water 20 11
Escherichia coli and
Enterococci
Event
are bacteria present in the gut of warm -blooded
animals. They should not be present in drinking
water and, if present, immediate action is
required to identify and remove any source of
faecal contamination that is found. The standard
is 0 per 100ml.
water companies have to inform the Inspectorate
about occasions when water quality or
sufficienc y is affected or when public confidence
in drinking water quality may be impacted. The
Inspectorate refer to these instances as ‘Events’ .
Filtration
Fluoride
Geosmin
Granular activated carbon
Gross alpha/gross beta
Groundwater
the separation of suspended particulate matter
from a fluid.
occurs naturally in many water sources,
especially groundwater. It cannot be removed by
conventional water treatment so high levels must
be reduced by blending with anoth er low fluoride
water source. Some water companies are
required by the local health authority to
fluoridate water supplies as a protection against
tooth decay. The drinking water standard
ensures levels are safe in either circumstance.
Fluoridation of water is a Department of Health
polic y. A European health-based standard of
1.5mg/l applies.
a substance produced by the growth of algae,
normally in surface waters which gives rise to a
characteristic ‘earthy’ or ‘musty’ taste or odour.
an adsorbent filtration media used to remove
trace organic compounds from water.
radioactivity in raw water can originate from
natural substances or from a specific point
emission. W ater companies are required to
screen for radionuclides that emit either alpha or
beta particles. If such screening exceeds guide
values (gross alpha 0.1Bq/l, gross beta 1.0Bq/l)
then fuller analysis for specific radionuclides is
carried out to determine the origin.
water from aquifers or other underground
sources.
56

W estern re gion
Hydrogen Ion
(pH)
Improvement programmes
Indicator organism
Indicator parameter
Information Letter
Inspectorate
Iron
Lead
m 3 /d
Manganese
gives an indication of the degree of acidity of the
water. A pH of 7 is neutral; values below 7 are
acidic and values above 7 are alkaline.
A low pH water may result in pipe corrosion.
This is corrected by adding an alkali during
water treatment. A specification of between
6.5 and 9.5 applies.
water company improvement works, these are
legally binding on the company and each
programme will remedy an actual or pote ntial
breach of a drinking water standard within a
specified time period.
an organism which indicates the presence of
contamination and hence the possible presence
of pathogens.
something that is measured to che ck that
control measures, such as water treatment,
are working effectively.
formal guidance to water companies given
by the Inspectorate and published on the
Inspectorate’s website at www.dwi.gov.uk
The Drinking W ater Inspectorate.
is present naturally in many water sources.
It is removed by water treatment. Some iron
compounds are used as water treatment
chemicals. However, the commonest source
of iron in drinking water is corrosion of iron
water mains. A national standard of
200μg/l applies.
very occasionally occurs naturally in raw waters,
but the usual reason for its presence in drinking
water is plumbing in older properties. If the water
supply has a tendenc y to dissolve lead then
water companies treat the water to reduce
consumer exposure. The permanent remedy is
for householders to remove lead pipes and
fittings. A European health-based standard of
25μg/l applies, but 10μg/l will apply from 25
December 2013 onwards.
cubic metre per day.
is present naturally in many sources and is
usually removed during treatment. A national
standard of 50μg/l applies.
57

Dri nking water 20 11
Mean zonal compliance
percentage
Mercury
Methyl-isoborneol (MIB)
mg/l
Microbiological
Ml/d
Nickel
Nitrate
Nitrite
Notice
a measure of compliance with drinking water
standards introduced by the Inspectorate in
2004.
is not found in sources of drinking water.
A European health-based standard of
1μg/l applies.
a natural substance produced by the growth of
algae, normally in surface waters which gives
rise to a characteristic ‘eart hy’ or ‘musty’ taste or
odour. It is detected by the method for assessing
taste and odour.
milligram per litre (one thousandth of a gram
per litre).
associated with the study of microbes.
megalitre per day (one Ml/d is eq uivalent to
1,000 m 3 /d, or to 220,000 gallons/d).
occurs naturally in some groundwater and where
necessary special treatment can be installed to
remove it. Another source of nickel in drinking
water is the coatings on modern taps and other
plumbing fittings. A European health-based
standard of 20μg/l applies.
occurs naturally in all source waters although
higher concentrations tend to occur where
fertilisers are used on the land. Nitrate can be
removed by ion exchange water treatment or
through blending with other low nitrate sources.
A European health-based standard of
50mg/l applies.
is sometimes produced as a by-product when
chloramine is used as the essential residual
disinfectant in a public water supply.
Chloramine is the residual disinfectant of choice
in large distributions systems because it is more
stable and long-lasting. Careful operation of the
disinfection process ensures levels of nitrite are
kept below the standard. A European health -
based standard of 0.5mg/l applies.
an instruction served by the Secretary of State
(in the case of water supplies, the Chief
Inspector of W ater) requiring specific actions to
be taken by the recipient within a specified
timescale.
58

W estern re gion
Odour
Ofwat
Oocyst
Organoleptic
Ozone process (ozonation)
Parameters
Pathogen
PCV
Periodic review
Pesticides
Pesticides – organochlorine
compounds (aldrin, dieldrin,
heptachlor, heptachlor
epoxide)
can arise as a consequence of natur al processes
in surface waters, particularly between late
spring and early autumn. W ater treatment with
activated carbon or ozone will remove natural
substances causing taste. The standard relates
to the evaluations of a panel of people assessing
samples in the laboratory.
the water industry’s economic regulator.
the resistant form in which Cryptosporidium
occurs in the environment, and which is capable
of causing infection.
characteristics of a substance as detected by ou r
senses, for example taste, odour or colour.
the application of ozone gas in drinking
water treatment.
the substances, organisms and properties listed
in Schedule 2 and Regulation 3 of the
regulations. Parameter definitions can be found
in this annex.
an organism which can infect humans and
cause disease.
see ‘Prescribed concentration or value’.
the economic regulator’s process of setting
water prices.
any fungicide, herbicide, insecticide or related
product (excluding medicines) used for the
control of pests or diseases.
are no longer used in the UK because they are
persistent in the environment. They are not found
in drinking water. A European chemical standard
of 0.03μg/l for each compound applies.
59

Dri nking water 20 11
Pesticides – other than
organochlorine compounds
Phosphate dosing
Plumbosolvency
Polycyclic aromatic
hydrocarbons
(PAHs)
Powdered activated carbon
(PAC)
Pre- and post-renovation
assessment (PPRA)
Prescribed concentration or
value (PCV)
Private supplies
Protozoan parasites
Public Register
is a diverse and large group of organic
compounds used as weed killers, in secticides
and fungicides. Many water sources contain
traces of one or more pesticides as a result of
both agricultural and non-agricultural uses,
mainly on crops and for weed control on
highways and in gardens. W here needed, water
companies have installed water treatment
(activated carbon and ozone) so that pesticides
are not found in drinking water. W ater companies
must test for those pesticides used widely in
their area of supply. Pesticide monitoring thus
varies according to risk. A European chemical
standard of 0.1μg/l for each individual substance
and 0.5μg/l for the total of all pesticides applies.
treatment of water that results in a protective
film building up on the inside of pipes minimising
the likelihood of lead being present in drinking
water supplied through lead pipes.
the tendenc y for lead to dissolve in water.
is a group name for several substances present
in petroleum -based products such as coal tar.
(see Benzo(a)pyrene listed above for more
information). A European health-based
standard of 0.1μg/l for the sum of all the
substances applies.
powdered activated carbon is employed in
treatment processes to remove pollutants.
a programme of assessment before and after
mains renovation to demonstrate justification
for the work, and the improvements achieved
by the renovation.
the numerical value assigned to drinking water
standards defining the maximal or minimal legal
concentration or value of a parameter.
water supplied for human consumption or food
production which is not provided by a water
undertaker or licensed water supplier.
a single cell organism that can only survive
by infecting a host.
drinking water quality information made available
to the public by water companies as required
by regulations.
60

W estern re gion
Public supplies
Raw water
Regulations
Remedial action
Residual disinfectant
Risk assessment
Secretary of State
Selenium
Service connection
Service pipe
Service reservoir
Sodium
Springs
water supplied by a company licensed for
that purpose.
water prior to receiving treatment for the purpose
of drinking.
The W ater Supply (W ater Quality) Regulations
2000 (England), 2010 (W ales).
action taken to improve a situation.
the small amount of chlorine or chloramines
present in drinking water to maintain its quality
as it passes through the water company’s
network of pipes and household plumbing.
a review undertaken to identif y actual or
potential hazards to human health in a water
treatment works and associated supply s ystem.
Prioritisation of risk is based on consideration of
likelihood and consequence of the risk occurring.
Secretary of State for Environment, Food
and Rural Affairs.
is an essential element and a neces sary dietary
component. Amounts in drinking water are
usually well below the standard. A European
health-based standard of 10μg/l applies.
connection between the water company's main
to a consumer’s property.
any pipe subject to mains water pressure or
subject to mains pressure but for the closing
of some valve.
a water tower, tank or other reservoir used
for the storage of treated water within the
distribution s ystem.
is a component of common salt. It is present
in seawater and brackish groundwater.
Some treatment chemicals contain sodium.
Concentrations in drinking water are extremely
low, but some water softeners can add
significant amounts to drinking water where they
are installed in homes or factories. A national
standard of 200mg/l applies.
groundwater appearing at the surface at the
outcrop of the junction of a permeable stratum
with an impermeable stratum.
61

Dri nking water 20 11
Sulphate
Supply pipe
Supply point
Surface water
Taste
Technical audit
Tetrachloroethane and
Trichloroethene
Tetrachloromethane
Time of supply
Total indicative dose
Total organic carbon
Toxicology
Treated water
occurs naturally in all waters and is difficult to
remove by treatment. An indicator parameter with
a guide value of 250mg/l.
see service pipe.
a point other than a consumer’s tap authorised
for the taking of samples for compliance with
the regulations.
untreated water from rivers, impounding
reservoirs or other surface water source.
can arise as a consequence of natural processes
in surface waters, particularly between late
spring and early autumn. W ater treatment with
activated carbon or ozone wil l remove natural
substances causing taste. The standard relates
to the evaluations of a panel of people assessing
samples in the laboratory.
the means of checking that water companies are
complying with their statutory obligations.
are solvents that may occur in groundwater in
the vicinity of industrial sites. W here necessary
they are removed by specialist treatment.
A European health-based standard of 10μg/l
for the sum of both substances applie s.
is a solvent that may occur in groundwater in the
vicinity of industrial sites. W here necessary it is
removed by specialist water treatment.
A national standard of 3 μg/l applies.
the moment when water passes from the water
company’s pipework into a consumer’s pipework.
is a measure of the effective dose of radiation
the body will receive from consumption of the
water. It is calculated only when screening
values for gross alpha or gross beta (radiation)
are exceeded. An indicator parameter with a
guide value of 0.10mSv/year.
represents the total amount of organic matter
present in water. An indicator parameter with
a guide value of ‘no abnormal change’.
the study of the health effects of substances.
water treated for use for domestic purposes as
defined in the regulations.
62

W estern re gion
Trihalomethanes
Tritium
Turbidity
Undertakings
Vinyl chloride
Water supply zone
WHO
Wholesome/wholesomeness
are formed during disinfection of water by a
reaction between chlorine and naturally occurring
organic substances. Their production is
minimised by good operational practice.
A European health-based standard of 100μg/l
applies.
is a radioactive isotope of hydrogen.
Discharges to the environment are strictly
controlled and there is a national programme
of monitoring surface waters. An indicator
parameter with a guide value of 100Bq/l.
is a measure of the cloudiness of water. At
treatment works, measurement is an important
non-specific water quality control parameter
because it can be monitored continuously on line
and alarms set to alert operators to deterioration
in raw water quality or the ne ed to optimise
water treatment. An indicator parameter with a
guide value of 1NTU. W hen detected at the
consumer’s tap it can arise from disturbance of
sediment within water mains. A national standard
of 4NTU applies in this case.
legally binding programmes of work agreed
between a water company and the Chief
Inspector of Drinking W ater to address actual
or potential water quality issues.
may be present in plastic pipes as a residual of
the manufacturing process of polyvinyl chloride
(PVC) water pipes. Its presence in drinking water
is controlled by product specification.
A European health-based standard of 0.5μg/l
applies.
a pre-defined area of supply for establishing
sampling frequencies, compliance with standards
and information to be made publicly available.
W orld Health Organisation.
a legal concept of water quality which is defined
by reference to standards and other
requirements set out in the regulations.
63

Dri nking water 20 11
Annex 3
Not significant and minor drinking water quality events
Nature Number of not significant and minor events Area affected (estimate of pop ulation affected)
Chemical 4 – BRL (1), SW T (1), W SX (1) Milborne St Andrew, Dorset (3)
Penzance, Cornwall (3)
W eston-Super-Mare and surrounding area
(108,652)
Discolouration 5 – SW T (2), W SX (3) Bridgwater, Somerset (2,870)
Exeter, Devon (1,200)
Taunton, Somerset (1,250)
Melksham, W iltshire (3,400)
Chasewater, Cornwall (4,125)
Loss of supplies/
poor pressure
5 – BRL (1), SW T (1), W SX (3) Fovant, W iltshire (90)
Minehead, Somerset (3,250)
St Ives, Cornwall (5,152)
W arminster, W iltshire (4,500)
Lympsham, Somerset (1,250)
Microbiological 8 – BRL (2), SW T (3), W SX (3) Bristol and W eston -Super-Mare (200,000)
Dorchester, Dorset (78)
Plymouth, Devon (3)
Bristol (3)
St Austell, Cornwall (5)
Taunton, Somerset (3)
Truro, Cornwall (3)
Hullavington, W iltshire (3)
Public concern 7 – BRL (1), SW T (3), W SX (3) Chittlehamholt, Devon (3)
Plympton, Devon (50)
Stock wood, Bristol (3)
Loxbeare, Devon (8)
Cherhill, W iltshire (3)
Shaftesbury, Dorset (5)
Litton Cheney (3)
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W estern re gion
Nature Number of not significant and minor events Area affected (estimate of pop ulation affected)
Taste or odour 6 – BRL (1), SW T (3), W SX (2) Crantock, Cornwall (3)
Bath (3)
Exeter, Devon (3)
W est Lulworth, Dorset (3)
W esterleigh, South Gloucestershire (100)
Truro, Cornwall (3)
Total 34 –BRL (6), SWT (13), WSX (15 ) 336,033
Significant, serious and major drinking water quality events
Date and
duration
25 May 2011
For 36 hours
(SW T)
Area
Estimate of
population
affected
Nature and cause of
the event
City of Truro 11,250 Discolouration due to
planned work.
Main actions and findings from the Inspectorate
investigation
South West Water Ltd action :
Repaired main.
Replaced faulty equipment.
Sampled affected area.
Flushed mains.
DWI comments and findings:
Suggested that the com pany annotates its mains records
to ensure that appropriate warning flag put on the key
valve.
Suggested that to meet the r equirements of the
Information Direction , where an event has a clear
second phase, the company continues to keep
stakeholders informed and acts in a proactive m anner.
Company did not forewarn customers.
Recommended advance notification of consumers in
planned work situations where risk of discolouration has
been identified.
The company was reminded of the contents of
Information Letter 16/2000 relating to warning
consumers and carrying out work on the network
resulting in discolouration to supplies.
Risk classification: Significant.
65

Dri nking water 20 11
Date and
duration
05 Jun 2011
For 38 hours
(BRL)
Area
Burnham on
Sea, Somerset
Estimate of
population
affected
Nature and cause of
the event
17,500 Loss of supplies with
media interest.
Main actions and findings from the Inspectorate
investigation
Bristol Water Plc action:
Repaired main.
Sampled affected area.
Provided bottled water on request.
Flushed mains.
The company made a repair to a strategic main following
large scale burst with m edia interest causing public
concern.
DWI comments and findings:
Did not notify Inspectorate – the company chose to email
the Inspectorate rather than use the cascade sys tem.
Reminded company of telephone cascade system which
must be used for first notification, e -mail is appropriate
only for follow-on comm unications.
Risk classification: Significant.
17 Jun 2011
For 24 hours
(SW T)
Exmouth and
East Devon
coastal area
93,085 Microbiological
contamination.
South West Water Ltd action:
Increased chlorine residuals in the distribution s ystem.
Sampled affected area.
Carried out a laboratory audit to verify the analytical
procedure and staff com petence.
Carried out sampler checks .
Inspections of treated water storage tanks.
DWI comments and findings:
Checks by company found nothing untoward.
The Inspectorate is content with th e actions taken by the
company.
No recommendations or suggestions made.
Risk classification: Significant.
66

W estern re gion
Date and
duration
21 Aug 2011
For 4 days
(SBW )
Area
East End,
Bucklers Hard
and East
Bolder
Villages, New
Forest,
Hampshire
Estimate of
population
affected
Nature and cause of
the event
2,150 Failure of the
disinfection s ystem.
Main actions and findings from the Inspectorate
investigation
Sembcorp Bournemouth Water Ltd action:
Flushed mains.
Sampled affected area.
Modified the system logic for th e forward predictive
dosing of sodium bisulphite to prevent further problems
with chloramination.
DWI comments and findings:
Unacceptable delay in notifying local/health authorities.
Unacceptable delay in notifying Inspectorate.
Samples not analysed for a ppropriate parameters.
Sampling was not timely enough.
Inadequate risk assessment.
Recommended adequate and timely samples are
collected as required by Regulation 10.
Recommended review and staff briefing about
responding to a rapidly changing situation cr eating a
large number of alarms, and putting in place a clear set
of escalation procedures .
Critical of failure to notify appropriate stakeholders.
Critical of failure to provide accurate documentation to
the Inspectorate.
Recommended that the company carr y out a risk
assessment including contingency measures, when
control critical equipment is removed for maintenance .
Critical that such a key part of the process was so slow
to react to changing conditions and that the company
had failed to recognise this p rior to the event.
Suggested that the com pany investigate any similar set -
ups at other sites and m ake corrections as required.
Risk classification: Significant.
67

Dri nking water 20 11
Date and
duration
01 Sep 2011
For 3 days
(BRL)
Area
Long Ashton,
North
Somerset
Estimate of
population
affected
Nature and cause of
the event
3,292 Discolouration due to
planned work.
Main actions and findings from the Inspectorate
investigation
Bristol Water Plc action:
Flushed mains.
Review of procedures.
Sampled affected area.
Improved procedures for updating GIS.
DWI comments and findings:
Inadequate contingenc y planning.
Samples not analysed for appropriate parameters in
contravention of Regulation 10.
Inadequate risk assessment.
Inadequate procedures.
Critical that the risk ass essment carried out in advance
of the work was based on a short section of main and
did not take into account the properties fed by the 24"
trunk main downstream of the new pipework. The new
pipework had been connected to an abandoned section
of main, geographic information system ( GIS) records
were incorrect and the main had been inadequately
capped off.
Recommendations were made in respect of risk
assessment procedures, GIS records, main capping.
25 Oct 2011
For 4 days
(SW T)
Cornwall , west
of Bodmin
Moor, supplied
by Restormel
works
3,773 Musty taste or odour
due to low levels of
methyl-isoborneol and
geosmin.
Risk classification: Significant.
South West Water Ltd action:
Sampled affected area.
Implemented/optimised powdered activated carbon
dosing at both works.
DWI comments and findings:
No recommendations or suggestions made.
Restormel works was subject to enforcement
(undertaking) for pesticides prior to this event. The
company has been evaluating the use of advanced
oxidation processes in c ombination with granular
activated carbon to provide a more robust barrier before
making a decision on the final solution. The work is due
to be completed b y 31 March 2014.
Risk classification: Significant.
68

W estern re gion
Date and
duration
04 Nov 2011
For 16 hours
(BRL)
Area
Broom Hill
Brislington,
Bristol
Estimate of
population
affected
Nature and cause of
the event
6,163 Discolouration due to
a burst main.
Main actions and findings from the Inspectorate
investigation
Bristol Water Plc action:
Repaired main.
Sampled affected area.
DWI comments and findings:
The Inspectorate sugges ted that the company make a
full risk assessment of any activity carried out by a third
party to assess the risks posed to water quality by
planned works and that these risks are fully documented
and mitigated against.
Risk classificatio n: Significant.
02 Dec 2011
For 3 weeks
(SW T)
Areas of
Helston and
the Lizard
Peninsula
supplied by
W endron
works
22,500 Evidence of chemical
contamination
(mecoprop).
South West Water Ltd action:
By-passed service reservoir.
Flushed mains.
Sampled affected area.
DWI Comments and findings:
Inadequate treatment process ; no dedicated organic
micro-pollutant barrier.
Powdered activated carbon dosing is in place as short -
term mitigation.
Catchment investigation and enhanced monitoring being
used to identify point sources of pollution and the
company has enhanced water quality monitoring in place
to identify any increases in pesticide levels at an early
stage.
Risk classification: Significant.
69

Dri nking water 20 11
Date and
duration
05 Dec 2011
For 3 days
(W SX)
Area
Trowbridge,
W iltshire
Estimate of
population
affected
Nature and cause of
the event
5,700 Loss of supplies due
to a burst main.
Main actions and findings from the Inspectorate
investigation
Wessex Water Services Ltd action:
Repaired main.
Sampled affected area.
Provided an alternative supply by tanker /bowser.
The company rezoned the area and repaired the main
that was damaged by a third party.
Alternative supply arrangements were provide d and
bottled water on request to those areas that could not be
fed reliably during the repair operation.
Flushing operations cleared the discolouration within 48
hours.
DWI comments and findings:
No recommendations o r suggestions made .
Risk classification: Significant.
13 Dec 2011
For 16 hours
(BRL)
Churchill,
Langford &
W rington,
Bristol
4,250 Discolouration due to
planned work.
Bristol Water Plc action:
Repaired main.
Sampled affected area.
Flushing operation cl eared the discolouration within
48 hours.
DWI comments and findings:
Suggestion that the com pany considers making a full
assessment of any activity involving third parties not
under the direct control of the company and appraises
the extent of potential risks to the planned operation and
water quality, and that the company subsequently
documents contingency and control measures arising
from any identified risks.
Risk classification: Significant.
70

W estern re gion
Date and
duration
20 Dec 2011
For 1 day
(SW T)
Area
Looe, St.
Blazey,
Liskeard and
surrounding
areas,
Cornwall
Estimate of
population
affected
Nature and cause of
the event
10,000 Microbiological
contamination.
Main actions and findings from the Inspectorate
investigation
South West Water Ltd action:
Sampled affected area.
Company removed Bodelver service reservoir from
service for cleaning and inspection. No issues were
identified at the service reservoir. The company have
started enabling works to allow the treated water tank at
St Cleer to be removed from supply and inspected.
DWI comments and findings:
No cause was identified for the microbiological failures.
Suggestion made that company should collect more
frequent, larger volume samples in response to any
future faecal coliform contamination detected at works.
Risk classification: Significant.
22 Dec 2011
For 3 days
(BRL)
Congyre Grove
near Bristol
30 Microbiological
contamination.
Bristol Water Plc action:
Repaired main.
Sampled affected area.
Made changes to company procedures.
DWI comments and findings:
No recommendations or suggestions made .
Risk classification: Significant.
71

Dri nking water 20 11
Annex 4
Planned drinking water quality improvements
Compan y
Parameter,
hazard or driver
Site
Due for
completion *
Status *
Legal
Instrument
BRL Cryptosporidium Cheddar 31-Dec-13 Ongoing Notice
BRL Cryptosporidium Littleton 31-Dec-12 Ongoing Notice
BRL Cryptosporidium Purton 31-Dec-11
Completed
05-Jan-12
Notice
BRL Cryptosporidium Shipton Moyne 31-Dec-12 Ongoing Notice
BRL Cryptosporidium Stowey 31-Dec-13 Ongoing Notice
BRL
Iron
Trunk mains
rehabilitation
31-Mar-15 Ongoing Undertaking
BRL Lead Sherborne 31-Jul-13 Ongoing Notice
BRL Metaldehyde Banwell catchment 31-Mar-15 Ongoing Undertaking
BRL
Metaldehyde
Littleton and
Purton catchments
31-Mar-15 Ongoing Undertaking
BRL Metaldehyde Stowey catchment 31-Mar-15 Ongoing Undertaking
BRL Nitrate Frome 04-Sep-14 Ongoing Undertaking
BRL
Total
Trihalomethanes
Littleton
31-Dec-11
Completed
15-Dec-12
Undertaking
CHO Nitrate Cholderton 31-Mar-13 Ongoing Undertaking
SBW
Coliform bacteria,
E.coli
Alderney
14-Feb-11
SBW Cryptosporidium W oodgreen 31-Dec-11
SBW
SW T
Iron, Turbidity
and Polycyclic
aromatic
hydrocarbons
Cryptosporidium,
Colour and
Turbidity
Completed
14-Feb-11
Completed
31-Dec-11
Undertaking
Notice
Distribution s ystem 31-Mar-15 Ongoing Undertaking
Bovey Cross
31-Mar-12
Completed
07-Jan-11
Notice
SW T Iron and Turbidity Greatwell 31-Dec-11 Delayed Undertaking
SW T
Lead
Drift, Restormel
Central, Dotton
and Pynes Central
SW T Manganese Tottiford 31-Mar-12
SW T Pesticides Drift 31-Mar-12
31-Mar-15 Ongoing Undertaking
Completed
12-Mar-12
Completed
30-Mar-12
Undertaking
Undertaking
SW T Pesticides Restormel 31-Mar-14 Ongoing Undertaking
SW T
SW T
Taste, Odour and
Manganese
Total
Trihalomethanes
Stithians
31-Mar-10
Completed
25-Jan-11
Undertaking
W endron 31-Dec-14 Ongoing Undertaking
W SX 2,4-D (pesticide) Fovant TBC Pending TBC
72

W estern re gion
Compan y
W SX
Parameter,
hazard or driver
Chlortoluron,
Isoproturon,
MCPA, MCPB,
2,4-D and
Metazachlor
Site
Friar W addon
Due for
completion *
31-Jan-11
Status *
Completed
01-Jan-12
Legal
Instrument
Undertaking
W SX Coliform bacteria Moorbrake Camp 31-Mar-13 Ongoing Notice
W SX
W SX
Contamination
from catchment
Contamination
from catchment
Brixton Deverill
Portesham
31-Mar-10
30-Sep-10
W SX Cryptosporidium Dewlish 31-Mar-12
Completed
23-Mar-12
Completed
07-Mar-11
Completed
07-Nov-11
Notice
Notice
Notice
W SX Cryptosporidium Dunkerton 31-Mar-13 Ongoing Notice
W SX Cryptosporidium Tatworth 31-Mar-13 Ongoing Notice
W SX Cryptosporidium Tollerdown 31-Mar-14 Ongoing Notice
W SX
Cryptosporidium
Upton Scudamore
Comb
31-Mar-12
Completed
11-Aug-11
Notice
W SX Cryptosporidium W iddenham 31-Mar-14 Ongoing Notice
W SX E.coli Grange 31-Mar-12
W SX E.coli Grove New 31-Mar-13
Completed
30-Mar-12
Completed
05-May-11
Notice
Notice
W SX E.coli Tucking Mill N/A Ongoing Notice
W SX Iron Danesborough 30-Jun-11
W SX
W SX
Iron, Manganese
and Turbidity
Isoproturon,
Pesticides,
Mecoprop,
Chlortoluron and
Taste and Odour
Trunk mains
renovation
Completed
30-Dec-11
Undertaking
31-Mar-15 Ongoing Undertaking
Sutton Bingham 31-Mar-14 Ongoing Undertaking
W SX Lead Distribution s ystem 31-Mar-15 Ongoing Undertaking
W SX
W SX
Metaldehyde
(pesticide)
Nitrate
Durleigh catchment 31-Mar-15 Ongoing Undertaking
Dunkerton,
Chirton, Fonthill
Bishop,
Sturminster
Marshall/Shapwick ,
Hooke, Bulbridge
and W ylye
31-Mar-18 Ongoing Undertaking
W SX Taste and Odour Blashford 31-Mar-14 Delayed Undertaking
*Dates used are those for the completio n of the agreed programme of work. There is a
further period of 12 months before a programme is officially closed to as certain the
benefits of the work to consumers.
73

Dri nking water 20 11
Delayed programmes
Compan y
Parameter, hazard
or driver
Site
Reason for dela y
SW T Iron and Turbidity Greatwell Commissioning issues
W SX Taste and Odour Blashford Change of solution
Acknowledged actions to sustain safe, clean drinking
water
Additional
acknowledged
actions to mitigate
risk
(as at Dec 2008)
Acknowledged actions
completed (as at Dec
2010)
Acknowledged actions
completed (as at Dec 2011)
38 25 26
74

W estern re gion
Annex 5
Competition in the water industry
The following table indicates the extent of competition in the water
industry in England and Wales.
Inset appointments in place in 2011
Site Appointee Incumbent and region Status
Shotton Paper,
Shotton
Albion W ater
Dŵr Cymru W elsh W ater,
W ales
Supplying
water
Buxted Chicken,
Flixton
Anglian W ater Essex and Suffolk W ater,
Central and Eastern region
Supplying
water
W ynyard, near
W olviston
Berryfields,
Aylesbury
Brooklands, Milton
Keynes
Great Billing W ay,
Northampton
Kings Cross,
London
Long Croft Road,
Corby
Priors Hall, Corby
The Bridge,
Dartford
Media City,
Salford Quays
Bromley Common,
Bromley
Farndon Road,
Market
Harborough
Graylingwell,
Chichester
Great W estern
Park, Didcot
Hale Village,
Tottenham
Kennet Island,
Reading
Kingsmere,
Bicester
Llanilid Park,
South W ales
New South
Quarter, Croydon
Park Views,
Epsom
Hartlepool W ater
Independent W ater
Networks Ltd
Independent W ater
Networks Ltd
Independent W ater
Networks Ltd
Independent W ater
Networks Ltd
Independent W ater
Networks Ltd
Independent W ater
Networks Ltd
Independent W ater
Networks Ltd
Peel W ater
Networks Ltd
SSE W ater
SSE W ater
SSE W ater
SSE W ater
SSE W ater
SSE W ater
SSE W ater
SSE W ater
SSE W ater
SSE W ater
Northumbrian W ater,
Northern region
Thames W ater, London and
South East region
Anglian W ater,
Central and Eastern region
Anglian W ater,
Central and Eastern region
Thames W ater, London and
South East region
Anglian W ater,
Central and Eastern region
Anglian W ater,
Central and Eastern region
Thames W ater, London and
South East region
United Utilities, Northern
region
Thames W ater, London and
South East region
Severn Trent W ater/ Anglian
W ater, Central and Eastern
region
Portsmouth W ater/Southern
W ater, London and South
East region
Thames W ater, London and
South East region
Thames W ater, London and
South East region
Thames W ater, London and
South East region
Thames W ater, London and
South East region
Dŵr Cymru W elsh W ater,
W ales
Thames W ater, London and
South East region
Thames W ater, London and
South East region
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
Supplying
water
75

Dri nking water 20 11
Site Appointee Incumbent and region Status
Riverside, Barking SSE W ater Essex and Suffolk
W ater/Thames W ater,
Central and Eastern region
The Portway, near
Salisbury
Fairfield Park and
Lower W ilbury
Farm, Arlesey
MoD Tidworth
near Andover
SSE W ater
Veolia W ater
Central
Veolia W ater
Projects
W essex W ater,
W estern region
Anglian W ater, Central and
Eastern region
W essex W ater,
W estern region
Supplying
water
Supplying
water
Supplying
water
Supplying
water
New inset appointments in 2011
Site Appointee Incumbent and
region
Kennet Island
(Phase 7), Reading
SSE W ater
Thames W ater,
London and South
East region
Status
Appointment
granted
76

W estern re gion
Annex 6
Water company indices
Bristol Water plc
Water supply arrangements
Company assets
Number of treatment works 17
Number of service reservoirs 169
Number of water supply zones 52
Length of mains pipe (km) 6,670
Population served
Population supplied 1,155,305
Number of local authorities 9
Water supplied
W ater supplied
301
(Ml/day)
Percentage from
81
surface sources
Percentage from
12
ground sources
Percentage from
7
mixed sources
Area of supply
Gloucestershire, Wiltshire, Bristol,
Somerset
Drinking water quality summary data
Company figure Industry average
2009 2010 2011 2011
Overall drinking water quality* 99.97% 99.96% 99.96% 99.96%
Water treatment
Process Control Index 100% 99.86% 99.99% 99.99%
Disinfection Index 100% 99.97% 99.99% 99.97%
Distribution systems
Distribution Maintenance Index 99.88% 99.89% 99.59% 99.88%
Reservoir Integrity Index 99.97% 99.99% 99.98% 99.96%
Building water systems
Parameters influenced by domestic
water s ystems
99.85% 99.96% 99.92% 99.87%
Consumer contacts
Company figure Industry average
2009 2010 2011 2011
Informing consumers
Total number 1,048 1,028 888 N/A
Rate per 1,000 population 0.94 0.90 0.77 1.21
Acceptability of water to
consumers
Total number 2,917 2,935 2,567 N/A
Rate per 1,000 population 2.63 2.58 2.22 1.91
Complaints to the Drinking Water Inspectorate
A total of 1 consumer of Bristol W ater plc directly contacted DW I in 2011.
Note: Sum m ary results for each com pan y of tests for indi vidual par am eters ar e suppl ied on
the DW I website at http:// www.dwi .gov.uk
* Ove ra ll dr inking wat er qu ality as rep resented by mean zon al com pliance for 39
par am eters .
77

Dri nking water 20 11
Cholderton and District Water Company Ltd
Water supply arrangements
Company assets
Number of treatment works 2
Number of service reservoirs 1
Number of water supply zones 1
Length of mains pipe (km) 30
Population served
Population supplied 2,100
Number of local authorities 2
Water supplied
W ater supplied
(Ml/day)
0.685
Percentage from
surface sources
0
Percentage from
ground sources
100
Percentage from
mixed sources
0
Area of supply
Small parts of Wiltshir e & Hampshire
Drinking water quality summary data
Company figure Industry average
2009 2010 2011 2011
Overall drinking water quality* 100% 100% 100% 99.96%
Water treatment
Process Control Index 100% 100% 100% 99.99%
Disinfection Index 100% 99.36% 100% 99.97%
Distribution systems
Distribution Maintenance Index 100% 100% 100% 99.88%
Reservoir Integrity Index 100% 100% 100% 99.96%
Building water systems
Parameters influenced by domestic
water s ystems
100% 100% 100% 99.87%
Consumer contacts
Company figure Industry average
2009 2010 2011 2011
Informing consumers
Total number 0 0 0 N/A
Rate per 1,000 population 0 0 0 1.21
Acceptability of water to
consumers
Total number 0 0 0 N/A
Rate per 1,000 population 0 0 0 1.91
Complaints to the Drinking Water Inspectorate
No consumers of Cholderton and District W ater Company Ltd directly contacted DW I
in 2011.
Note: Sum m ary results for each com pan y of tests for indi vid ual par am eters ar e suppl ied on
the DW I website at http:// www.dwi.gov.uk
* Ove ra ll dr inking wat er qu ality as rep resented by mean zon al com pliance for 39
par am eters .
78

W estern re gion
Semcorp Bournemouth Water Ltd
Water supply arrangements
Company assets
Number of treatment works 8
Number of service reservoirs 20
Number of water supply zones 10
Length of mains pipe (km) 2,808
Population served
Population supplied 430,000
Number of local authorities 6
Water supplied
W ater supplied
148
(Ml/day)
Percentage from
85
surface sources
Percentage from
15
ground sources
Percentage from
0
mixed sources
Area of supply
Parts of Dorset, Hampshire and
Wiltshire
Drinking water quality summary data
Company figure Industry average
2009 2010 2011 2011
Overall drinking water quality* 99.99% 99.94% 99.98% 99.96%
Water treatment
Process Control Index 99.99% 100% 100% 99.99%
Disinfection Index 99.90% 99.87% 99.95% 99.97%
Distribution systems
Distribution Maintenance Index 100% 100% 99.82% 99.88%
Reservoir Integrity Index 99.95% 100% 100% 99.96%
Building water systems
Parameters influenced by domestic
water s ystems
99.96% 99.73% 99.95% 99.87%
Consumer contacts
Company figure Industry average
2009 2010 2011 2011
Informing consumers
Total number 263 292 380 N/A
Rate per 1,000 population 0.62 0.68 0.89 1.21
Acceptability of water to
consumers
Total number 570 505 477 N/A
Rate per 1,000 population 1.34 1.18 1.12 1.91
Complaints to the Drinking Water Inspectorat e
No consumers of Semcorp Bournemouth W ater Ltd directly contacted DW I in 2011.
Note: Sum m ary results for each com pan y of tests for indi vidual par am eters ar e suppl ied on
the DW I website at http:// www.dwi.gov.uk
* Ove ra ll dr inking wat er qu ality as rep resented by mean zon al com pliance for 39 par am eters .
79

Dri nking water 20 11
South West Water Ltd
Water supply arrangements
Company assets
Number of treatment works 31
Number of service reservoir s 312
Number of water supply zones 32
Length of mains pipe (km) 15,000
Population served
Population supplied 1,696,000
Number of local authorities 17
Water supplied
W ater supplied
433
(Ml/day)
Percentage from
93
surface sources
Percentage from
6
ground sources
Percentage from
1
mixed sources
Area of supply
Devon, Cornwall, Somerset (part),
Dorset (part)
Drinking water quality summary data
Company figure Industry average
2009 2010 2011 2011
Overall drinking water quality* 99.98% 99.97% 99.99% 99.96%
Water treatment
Process Control Index 100% 100% 100% 99.99%
Disinfection Index 99.98% 99.97% 99.97% 99.97%
Distribution systems
Distribution Maintenance Index 99.91% 99.89% 99.94% 99.88%
Reservoir Integrity Index 99.93% 99.93% 99.97% 99.96%
Building water systems
Parameters influenced by domestic
water s ystems
99.97% 99.91% 99.97% 99.87%
Consumer contacts
Company figure Industry average
2009 2010 2011 2011
Informing consumers
Total number 1,951 1,812 1,113 N/A
Rate per 1,000 population 1.16 1.08 0.66 1.21
Acceptability of water to
consumers
Total number 14,675 11,085 11,653 N/A
Rate per 1,000 population 8.72 6.59 6.87 1.91
Complaints to the Drinking Water Inspectorate
A total of 3 consumers of South W est W ater Ltd directly contacted DW I in 2011.
Note: Sum m ary results for each com pan y of tests for indi vidual par am eters ar e suppl ied on
the DW I website at http:// www.dwi.gov.uk
* Ove ra ll dr inking wat er qu ality as rep resented by mean zon al com pliance for 39 par am eters .
80

W estern re gion
SSE Water
Water supply arrangements
Company assets
Number of treatment works 0
Number of service reservoirs 0
Number of water supply zones 11
Length of mains pipe (km) 22
Population served
Population supplied 5,000
Number of local authorities 12
Water supplied
W ater supplied
0.661
(l/day)
Percentage from
39
surface sources
Percentage from
48
ground sourc es
Percentage from
13
mixed sources
Area of supply
Old Sarum, near Salisbury;
Hale Village, Tottenham; Graylingwell,
Chichester; Bromley Common,
Bromley; Kennet Island, Reading; Park
Views, Epsom; Llanilid Park, South
Wales; Kingsmere, Bicester; Great
Western Park, Didcot; Barking
Riverside, Barking; Farndon Road,
Market Harborough
Drinking water quality summary data
Company figure Industry average
2009 2010 2011 2011
Overall drinking water quality* 100% 100% 100% 99.96%
Water treatment
Process Control Index N/A N/A N/A 99.99%
Disinfection Index N/A N/A N/A 99.97%
Distribution systems
Distribution Maintenance Index 100% 100% 100% 99.88%
Reservoir Integrity Index N/A N/A N/A 99.96%
Building water systems
Parameters influenced by domestic
water s ystems
100% 100% 100% 99.87%
Consumer contacts
Company figure Industry average
2009 2010 2011 2011
Informing consumers
Total number 1 1 2 N/A
Rate per 1,000 population 0.74 0.5 0.39 1.21
Acceptability of water to
consumers
Total number 0 2 2 N/A
Rate per 1,000 population 0 0.99 0.39 1.91
Complaints to the Drinking Water Inspectorate
No consumers of SSE W ater directly contacted DW I in 2011.
Note: Sum m ary results for each com pan y of tests for indi vidual par am eters ar e suppl ied on
the DW I website at http:// www.dwi.gov.uk
* Ove ra ll dr inking wat er qu ality as rep resented by mean z on al com pliance for 39 par am eters .
81

Dri nking water 20 11
Veolia Water Projects Ltd
Water supply arrangements
Company assets
Number of treatment works 2
Number of service reservoirs 6
Number of water supply zones 1
Length of mains pipe (km) 98
Population served
Population supplied 8,000
Number of local authorities 1
Water supplied
W ater supplied
(Ml/day)
Percentage from
surface sources
Percentage from
ground sources
Percentage from
mixed sources
Area of supply
Tidworth, Wiltshire
4
0
100
0
Drinking water quality summary data
Company figure Industry average
2009 2010 2011 2011
Overall drinking water quality* 100% 100% 100% 99.96%
Water treatment
Process Control Index 100% 100% 100% 99.99%
Disinfection Index 100% 100% 100% 99.97%
Distribution systems
Distribution Maintenance Index 100% 100% 100% 99.88%
Reservoir Integrity Index 100% 100% 100% 99.96%
Building water systems
Parameters influenced by domestic
water s ystems
100% 100% 100% 99.87%
Consumer contacts
Company figure Industry average
2009 2010 2011 2011
Informing consumers
Total number 16 1 0 N/A
Rate per 1,000 population 1.74 0.12 0 1.21
Acceptability of water to
consumers
Total number 3 6 4 N/A
Rate per 1,000 population 0.33 0.73 0.48 1.91
Complaints to the Drinking W ater Inspectorate
No consumers of Veolia W ater Projects Ltd directly contacted DW I in 2011.
Note: Sum m ary results for each com pan y of tests for indi vidual par am eters ar e suppl ied on
the DW I website at http:// www.dwi.g ov.uk
* Ove ra ll dr inking wat er qu ality as rep resented by mean zon al com pliance for 39 par am eters .
82

W estern re gion
Wessex Water Services Ltd
Water supply arrangements
Company assets
Number of treatment works 95
Number of service reservoirs 301
Number of water supply zones 91
Length of mains pipe (km) 11,500
Population served
Population supplied 1,237,680
Number of local authorities 15
Water supplied
W ater supplied
337
(Ml/day)
Percentage from
27
surface sources
Percentage from
71
ground sources
Percentage from
2
mixed sources
Area of supply
Large parts of Somerset, Dorset and
Wiltshire, small areas of
Gloucestershire and Devon
Drinking water quality summary data
Company figure
Industry average
2009 2010 2011 2011
Overall drinking water
quality*
99.95% 99.98% 99.98% 99.96%
Water treatment
Process Control Index 100% >99.99% 100% 99.99%
Disinfection Index 99.90% 99.95% >99.99% 99.97%
Distribution systems
Distribution Maintenance Index 99.97% 99.97% 99.91% 99.88%
Reservoir Integrity Index 99.97% 99.98% 99.96% 99.96%
Building water systems
Parameters influenced by
domestic water s ystems
99.80% 99.94% 99.92% 99.87%
Consumer contacts
Company figure Industry average
2009 2010 2011 2011
Informing consumers
Total number 1,157 1,051 1,066 N/A
Rate per 1,000 population 0.98 0.81 0.86 1.21
Acceptability of water to
consumers
Total number 3,845 3,224 2,988 N/A
Rate per 1,000 population 3.26 2.47 2.41 1.91
Complaints to the Drinking Water Inspectorate
No consumers of W essex W ater Services Ltd directly contacted DW I in 2011.
Note: Sum m ary results for each com pan y of tests for indi vidual par am eters ar e suppl ied on
the DW I website at http:// www.dwi.gov.uk
* Ove ra ll dr inking wat er qu ality as rep r esented by mean zon al com pliance for 39 par am eters .
83

Dri nking water 20 11
Annex 7
Information relating to public water supplies published by the
Inspectorate in 2011
Information Letters
Ref
Title
01/2011 Amendment to The Water Supply (Water Quality) Regulations
2010 (Wales)
02/2011 DWI Enforcement Policy
03/2011 Publication of World Health Organisation (WHO) document
entitled 'Water safety in buildings'
04/2011 Guidance on the general provisions for monitoring of parameters
relevant to radioactivity
05/2011 Production, delivery, receipt and control of water treatment
chemicals
06/2011 Technical Audit of Water Companies under Section 86 of the
Water Industry Act 1991: Publication of the report following the
audit of STS Analytical Services at Bridgend
07/2011 Implementation of the new SCA blue book 233: The
determination of taste and odour in drinking waters (2010)
08/2011 Publication of report: Objectionable taste and odour in water
supplies in North-East London between January and March 2010
The letters , an d thei r asso c iated anne xes, can be found on the Inspector ate’s website at
http://dwi.defra.go v.uk/stakeholders /inform ation -l etters /inde x.htm
Technical guidance
DWI Approval of Enterolert-DW® Quanti-Tray® method for the
determination of Enterococci in drinking water s
Copi es of the abo ve gui da nce can be foun d on the Inspectorat e’s we bsite at
http://dwi.defra.go v.uk/stakeholders /guidance -a nd -codes -of-p ractice/
84

W estern re gion
Research
Ref
DWI 70/2/260
DWI 70/2/245
DWI 70/2/224
DWI 70/2/242
DWI 70/2/253
DWI 70/2/255
DWI 70/2/208
WRF 4006
DWI 70/2/225
DWI 70/2/189
Title
Alternatives to phosphate for plumbosolvency control
Investigation of instances of low or negative pressures in
UK drinking water systems
Analytical methods for predicted disinfection by -products
of probable toxicological significance
Evaluation of haloacetic acid concentrations in trea ted
drinking water (Cranfield University)
Evaluation of haloacetic acid concentrations in treated
drinking water (WRc plc)
A review of fungi in drinking water and the implications for
human health
Critical assessment of implementing desalination
technology
An investigation of leaching from flexible rising mains
leading from borehole pumps
Water Safety in Buildings
Copi es of res ea rc h re po rts and exec utive summ aries can be foun d o n the Inspec torate’s websit e
at http://dwi. defra.go v.uk/researc h/com pleted -res ea rc h/20 00todate. htm
85

Dri nking water 20 11
Annex 8
Distribution of private water supplies
South West
86

W estern re gion
Local authorities
Key
Forest of Dean District Council 1
Gloucester City Council 2
Tewkesbury Borough Council 3
Cheltenham Borough Council 4
Stroud District Council 5
Cots wold District Council 6
South Gloucestershire Council 7
W iltshire Council 8
Swindon Borough Counc il 9
North Somerset District Council 10
Bristol City Council 11
Bath and North East Somerset District Council 12
North Devon District Council 13
W est Somerset District Council 14
Sedgmoor District Council 15
Mendip District Council 16
Torridge District Council 17
Mid Devon District Council 18
Taunton Deane Borough Council 19
South Somerset District Council 20
North Dorset District Council 21
East Dorset District Council 22
Cornwall Council 23
W est Devon Borough Council 24
Teignbridge District Council 25
Exeter City Council 26
East Devon District Council 27
W est Dorset District Council 28
W eymouth and Portland Borough Council 29
Purbeck District Council 30
Poole Borough Council 31
Bournemouth Borough Council 32
Christchurch Borough Council 33
Plymouth City Council 34
South Hams District Cou ncil 35
Torbay Council 36
87

Drinking Drinking Water Inspectorate Water Inspectorate | Ergon House, | 55, Whitehall Horseferry | London Road | | London SW1A 2EY | SW1P | Tel: 2AL 020 | Tel: 7270300 337068 6400
http://www.dwi.gov.uk
PB 13777