The Drinking Water Inspectorate is warning that the water sector in England faces significant long-term challenges on asset health and resilient water supplies.

The warning comes in the Chief Inspector’s Annual Report 2025 for England published by the Drinking Water Inspectorate - introducing the report, Marcus Rink, Chief Inspector of Drinking Water said:

“Consumers in England and Wales should have continued confidence that their drinking water is amongst the highest quality in the world. This year’s report shows that 99.97% of regulatory samples collected from public water supplies met the stringent standards in place to protect public health.

“While drinking water quality remains high, the industry faces significant long-term challenges. This report highlights concerns regarding asset health, particularly of tanks and service reservoirs. Additionally, ensuring sufficient and resilient water supplies is becoming an increasingly pressing issue and one of public concern due to its widespread impacts to communities and the economy. Addressing these challenges will require sustained investment, innovation and effective regulation.

“This report demonstrates the repercussions to companies when they fail in their duties to supply wholesome drinking water to consumers. As the government takes forward wider reforms through the Clean Water Bill and plans for a single water regulator, it is vital that focus remains on protecting public health and maintaining the high standards that consumers rightly expect. The Inspectorate will continue to provide independent evidence-based oversight to help secure safe, resilient and reliable drinking water now and for future generations.”

The warning comes despite the fact that public water supplies in England complied with regulatory standards in 99.97% of tests in 2025, across over 3.5 million samples taken.

Asset health - asset renewal and timely remediation are critical levers for protecting consumers

Commenting on asset health, the report says asset condition remains a critical factor in protecting drinking water quality. In 2025, there were 49 coliform compliance failures at treatment works and 65 at service reservoirs, alongside three E. coli detections at treatment works and four at service reservoirs, from a total of 3,632,669 microbiological tests. Ingress into contact tanks, treated water tanks and service reservoirs remains a recurrent and preventable risk. The Inspectorate’s findings make clear that asset renewal and timely remediation are critical levers for protecting consumers.

Water quality events - 47 events attributed directly to poor asset health or plant failure

During 2025, 586 water quality events were reported to the Inspectorate consisting of:

• 0 major events
• 7 serious events
• 168 significant events
• 162 minor events
• 241 not significant events

Of these, 217 of the reported events (37%) occurred on consumer premises and were attributed to the consumers distribution system. The Inspectorate uses the Event Risk Index (ERI) which measures the impact of events on consumers.

However, in 2025, the combined ERI score for England was 2,014, with 47 events attributed directly to poor asset health or plant failure, including 30 microbiological contamination events and 17 structural failures affecting treatment works, treated water tanks or service reservoirs.

During the year the Inspectorate completed 39 audits across England, spanning on-site inspections, whole-company audits and remote vertical audits with 205 recommendations being made to water companies. Audit themes included the condition and management of air valves, the adequacy of bottled water storage and emergency arrangements, and the robustness of data management systems. The report says the findings reinforce that effective asset oversight and data governance are fundamental to protecting drinking water quality.

PFAS: PFAS remain a significant focus for the Inspectorate. In 2025, companies carried out more than 635,000 analyses in England for individual PFAS, bringing the total since 2012 to more than 2.3 million analyses for both England and Wales. Companies have now implemented reporting for the ‘sum of PFAS’ based on the calculation of the results of analysis from all 48 named PFAS. In 2025, there were two tests at or above the Inspectorate’s guidance value of 0.1 ug/L for PFAS in England - both tests (PFOS) were taking from the same site (Southern Water) and blending is in place to ensure concentrations reaching consumers are below the guidance value.

Lead: There were 60 compliance sample failures for lead in 2025 from 14,122 samples analysed, with a maximum concentration reported of 562 µg/L. The primary source of lead in drinking water remains lead pipes and internal plumbing in older properties however failures have also started to be reported in new buildings. Water companies have collectively declared an ambition to be lead pipe free by 2050, and the Inspectorate continues to work with industry and government to drive progress toward that goal.

Consumer contacts: In 2025, water companies in England received 57,759 consumer contacts relating to the appearance, taste or odour of drinking water. Of these, 24,810 were for brown, black or orange discolouration, producing a contact rate of 0.42 per 1,000 consumers. While previous years had seen a gradual improvement in discolouration rates, that progress has now stalled, with the rate remaining flat since 2024. The Inspectorate treats this trend seriously: discolouration, though rarely a direct health risk, undermines consumer confidence and is a key indicator of network condition and operational control. Companies with persistent or deteriorating performance remain subject to regulatory scrutiny and enforcement action.

Enforcement: The Inspectorate holds a range of enforcement powers to compel companies to deliver drinking water of the highest quality and to ensure the systems underpinning its supply are sufficiently resilient. In 2025, 109 notices were served and five companies – Southern Water, Thames Water, South West Water, Northumbrian Water and South East Water and are subject to transformation programmes, the most significant step the Inspectorate can take where systemic or repeated failures require company-wide change.

This year, the Inspectorate also introduced a new Enforcement Performance Metric to measure how effectively companies are delivering against the obligations set out in their legal instruments.

The metric, published for the first time in thE report, identifies South East Water, Southern Water, South West Water and Anglian Water as outlier companies. The Inspectorate will use this metric to direct regulatory resource and to hold companies publicly accountable for delivery.

Click here to access the report online