Table of contents

• Drinking Water 2025 – Summary of the Chief Inspector’s report for drinking water in England
• Foreword
• Water supplies and testing
• Compliance with water quality standards
• Learning from microbiological failures
• Learning from turbidity failures
• Learning from chemical, taste and odour failures
• Learning from pesticide failures
• Asset health and service reservoir integrity
• Consumer contacts
• Drinking water quality events
• Water safety planning and risk assessment
• Perfluoroalkyl and polyfluoroalkyl substances (PFAS)
• Audit programme completed by the Inspectorate
• Air valve audits
• Enforcement, transformation and recommendations
• Materials in contact with drinking water (regulation 31)
• Security and Emergency Measures Direction - SEMD
• Network and Information Systems - NIS
• Research publications
• Whistleblowers
• Working with stakeholders
• Annex A – Number of tests carried out by companies
• Annex B – Compliance with standards
• Annex C – Compliance failures and events

Annex B – Compliance with standards

Microbiological compliance at water treatment works

Parameter	Standard	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard per company	Percent compliance (3dp)
Clostridium Perfringens (sulphite-reducing clostridia) (confirmed)	0 number/100 ml	22,563	4	BRL(1), IWN(1), SRN(1), SST(0), SWB(1)	99.982%
Turbidity – indicator	1 NTU	171,559	11	ANH(2), PRT(1), SRN(2), SVT(1), SWB(1), TMS(4)	99.994%
E. coli (confirmed)	0 number/100 ml	171,595	3	BRL(1), NES(1), TMS(1)	99.998%
Total coliforms (confirmed)	0 number/100 ml	171,667	52	AFW(3), ANH(4), BRL(4), NES(3), SEW(5), SRN(6), SST(2), SVT(4), TMS(10), UUT(5), WSX(1), YKS(5)	99.970%
Total		537,384	70

Table 22 – Microbiological compliance at water treatment works

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Microbiological compliance at service reservoirs

Parameter	Standard	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard per company	Percent compliance
E. coli (confirmed)	0 number/100 ml	182,507	4	YKS(3) SEW(1)	99.998%
Total coliforms (confirmed)	0 number/100 ml	182,576	75	SEW(8) TMS(3) YKS(25) SVT(4) NES(4) CAM(1) UUT(8) AFW(1) SWB(4) BRL(1) WSX(5) SRN(5) ANH(6)	99.959%
Total		365,083	79

Table 23 – Microbiological compliance at service reservoirs

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Microbiological compliance at consumers’ taps (water supply zones)

Parameter	Standard	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard per company	Number due to consumer distribution systems	Percent compliance
Coliform bacteria (indicator)	0 number/100 ml	156,979	366	BRL(9) SST(5) TMS(63) LNW(5) NES(33) SWB(11) AFW(15) MUA(1) WSX(10) CAM(1) SRN(13) SEW(9) YKS(50) ICW(5) PRT(3) ANH(21) UUT(44) IWN(11) SVT(59)	260	99.767%
E. coli (confirmed)	0 number/100 ml	156,951	26	ANH(1) SRN(1) PRT(1) AFW(4) TMS(7) SEW(1) NES(2) IWN(1) YKS(1) SVT(3) UUT(4)	21	99.983%
Enterococci (confirmed)	0 number/100 ml	14,084	8	BRL(1) YKS(2) SWB(2) AFW(2) NES(1)	5	99.943%
Total		328,014	400		286	99.878%

Table 24 – Microbiological compliance at consumers’ taps (water supply zones)

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Out of 400 microbiological failures at consumers taps, 286 of these have been directly associated with the consumers distribution system. There were 119 failures where, despite a satisfactory investigation the company was unable to identify the cause. A further 24 sample failures resulted in the inspectorate taking enforcement action with one suggestion, 20 recommendations and three legal instruments. Of the remaining following investigation they have been assessed as unlikely to recur.

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Detection of E. coli and Enterococci at treatment works, service reservoirs and consumers’ taps, by company

Company	E. coli in water leaving treatment works	E. coli in water leaving service reservoirs	E. coli at consumers’ taps	Enterococci at consumers’ taps
AFW	0 – 13,272	0 – 8,047	4 – 9,863	2 – 697
ALB	0 – 0	0 – 0	0 – 29	0 – 15
ANH	0 – 21,271	0 – 15,213	1 – 13,243	0 – 1281
AWI	0 – 0	0 – 0	0 – 27	0 – 24
BRL	1 – 2,977	0 – 7,522	0 – 3,212	1 – 230
CAM	0 – 2869	0 – 1,435	0 – 960	0 – 61
ESP	0 – 0	0 – 0	0 – 336	0 – 119
ICW	0 – 0	0 – 0	0 – 732	0 – 271
IWN	0 – 0	0 – 0	1 – 2,355	0 – 797
LNW	0 – 0	0 – 0	0 – 986	0 – 342
MTX	0 – 0	0 – 0	0 – 12	0 – 4
MUA	0 – 0	0 – 0	0 – 37	0 – 12
NES	1 – 9,927	0 – 15,207	2 – 11,973	1 – 919
PRT	0 – 3,346	0 – 1,628	1 – 1,969	0 – 119
SES	0 – 2,097	0 – 1,772	0 – 1,920	0 – 176
SEW	0 – 12,145	1 – 11,019	1 – 5,746	0 – 568
SRN	0 – 12,443	0 – 11,296	1 – 6,917	0 – 564
SST	0 – 4,116	0 – 1,572	0 – 3,553	0 – 223
SVT	0 – 21,861	0 – 22,130	3 – 22,843	0 – 1727
SWB	0 – 8,586	0 – 14,641	0 – 5,992	2 – 546
TMS	1 – 17,802	0 – 19,468	7 – 26,211	0 – 2050
UUT	0 – 16,354	0 – 17,255	4 – 19,875	0 – 1816
VWP	0 – 159	0 – 313	0 – 48	0 – 8
WSX	0 – 8,199	0 – 16,276	0 – 3,746	0 – 515
YKS	0 – 14,127	3 – 17,705	1 – 14,364	2 – 1000

Table 25 – Number of failures followed by total number of samples taken

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Chemical parameters

Parameter name	Standard	Total number of tests	Tests not meeting the standard	Tests not meeting the standard per company
1,2-Dichloroethane	3 µg/L	7,857	0
Benzene	1 µg/L	7,833	0
Pesticides (total by calculation)	0.5 µg/L	3,455	0
Trichloroethene & Tetrachloroethene – sum of 2 substances	10 µg/L	11,156	1	ESP (1)
Tetrachloromethane	3 µg/L	11,252	0
Benzo[a]Pyrene (total)	0.01 µg/L	13,644	1	SVT (1)
Polycyclic aromatic hydrocarbons (total by calculation)	0.1 µg/L	13,886	3
Trihalomethanes (total by calculation)	100 µg/L	14,175	0
Aluminium	200 µg/L Al	52,398	10	BRL (1), NES (4), UUT (5)
Arsenic	10 µg/L As	13,554	0
Bromate	10 µg/L BrO₃	10,026	1	ESP (1)
Cadmium	5 µg/L Cd	13,558	0
Cyanide	50 µg/L CN	3,654	0
Chromium	50 µg/L Cr	13,494	0
Iron	200 µg/L Fe	53,039	98	NES(9) SWB(7) AFW(1) SRN(3) SST(1) TMS(6) SEW(7) SVT(15) ANH(6) IWN(1) BRL(2) YKS(20) LNW(1) UUT(18) WSX(1)
Mercury	1 µg/L Hg	3,659	0
Manganese	50 µg/L Mn	52,918	18	NES(3) WSX(1) SVT(2) UUT(7) SWB(3) LNW(1) BRL(1)
Nickel	20 µg/L Ni	14,081	72	WSX(3)  BRL(4) YKS(7) NES(2) TMS(20) AWI(2)  IWN(3) SES(2) UUT(3)  LNW(5) SST(1) ANH(3) ESP(3)  SVT(6) MUA(1) AFW(3) SEW(1) SRN(3)
Lead	10 µg/L Pb	14,120	60	YKS(6) SST(3)  VWP(1)   SWB(1) AFW(6) NES(5)  SRN(3) SEW(3) IWN(2) AWI(2) UUT(7) WSX(1) ANH(2) ICW(1) SVT(4)  TMS(13)
Antimony	5 µg/L Sb	13,474	0
Selenium	10 µg/L Se	13,100	0
Electrical conductivity	2500 µS/cm at 20°C	48,731	0
Gross beta	1 Bq/L	1,254	0
Tritium	100 Bq/L	929	0
Gross alpha	0.1 Bq/L	1,257	15	ESP(4) LNW(1) IWN(10)
Odour	Acceptable to consumers and no abnormal change	57,660	48	UUT(4) TMS(1) ICW(1) ESP(1) NES(10) BRL(2) SRN(7) SWB(4) ANH(8) AFW(1) YKS(3) SST(2) SVT(5)
Taste (quantitative)	Acceptable to consumers and no abnormal change	57,502	72	SRN(6) UUT(5) SVT(6)  SWB(8) YKS(5) PRT(1) ESP(1) IWN(6) ANH(17) TMS(6) NES(7) WSX(3) BRL(2)
Residual disinfectant – free	2 mg/L	112,910	0
Residual disinfectant – total	2 mg/L	134,171	0
Boron	1 mg/L B	7,114	0
Copper	2 mg/L Cu	13,785	2	ANH(1) WSX(1)
Fluoride	1.5 mg/L F	10,334	0
Sodium	200 mg/L Na	14,071	1	NES (1)
Ammonium (zone)	0.5 mg/L NH₄	39,132	0
Nitrite – consumers taps	0.5 mg/L NO₂	24,557	5	TMS(4) NES(1)
Nitrate	50 mg/L NO₃	24,518	5	ANH(1) IWN(1)
Colour	20 mg/L Pt/Co	57,066	0
Sulphate	250 mg/L SO₄	7,738	0
Total indicative dose (gross alpha and beta)	0.1 mSv/year	15	0
Hydrogen ion (pH) – zone	6.5 – 9.5 pH Value	57,141	0
Total		1,023,218	410

Table 26 – chemical parameter sample numbers and number of failures

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Pesticide parameters – all

Parameter name	Standard	Total samples	Total failures	Detected pesticides
Individual Pesticides	0.1 µg/L	250,326	3	Propyzamide (2), Dieldrin (1)

Table 27 – individual pesticide sample numbers and number of failures

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Pesticide failures – named parameters

Pesticide name	Standard	Total samples	Total failures
Aldrin	0.1 µg/L	4237	0
Propyzamide	0.1 µg/L	5927	2
Dieldrin	0.1 µg/L	4790	1
Bentazone	0.1 µg/L	5877	0
Total			3

Table 28 – individual pesticide sample numbers and number of failures – by exception

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