DWI flags asset health for attention as it reports 99.97% compliance in 2025

(by Karma Loveday)

Drinking water quality in England remained of super-high quality in 2025, at 99.97% compliance. Publishing the Drinking Water Inspectorate’s (DWI) 2025 annual report, chief inspector Marcus Rink urged that focus remain on keeping standards up as water is reformed. He said: “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.”

He flagged up “significant long-term challenges” that need attention. “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.”

The DWI highlighted the following key headlines from the 2025 report:

Compliance: Public water supplies in England complied with regulatory standards in 99.97% of tests in 2025, across over 3.5m samples taken. Of the 982 failures, 447 were related to consumers’ own distribution systems. Parameter group compliance rates included: chemical parameters (99.95%), indicator parameters (99.97%), microbiological parameters (99.98%) and pesticides (99.99%). The Compliance Risk Index (CRI), which measures the risk to consumers from non-compliance, showed a decrease from 2024 with a score of 2.702.   

Events: 586 water quality events were reported to the Inspectorate in 2025, with no major events, seven serious events, 168 significant events, 162 minor events and 241 not significant events. 217 of these reported events (37%) occurred on consumer premises and were attributed to consumers' distribution systems. In 2025, the combined Event Risk Index (ERI) score for England, which measures the impact of events on consumers, was 2,014. 47 events were 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.

Audits: The Inspectorate completed 39 audits across England in 2025, 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. Findings reinforced that effective asset oversight and data governance are fundamental to protecting drinking water quality.

PFAS: PFAS remained 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 2.3m 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. There was one site under Wessex Water which reported ‘sum of PFAS’ above the Inspectorate’s guidance value of 0.1 ug/L in 2025 and three others across water companies.

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.

Asset health: Asset condition remained 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 remained a recurrent and preventable risk. The Inspectorate’s findings make clear that asset renewal and timely remediation are critical levers for protecting consumers.

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 stalled in 2025, with the rate remaining flat since 2024. The Inspectorate treated this trend seriously, arguing that discolouration, though rarely a direct health risk, undermines consumer confidence and is a key indicator of network condition and operational control. It warned that companies with persistent or deteriorating performance remain subject to regulatory scrutiny and enforcement action.

Enforcement: 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. For 2025, 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 this report, identified South East Water, Southern Water, South West Water and Anglian Water as outlier companies. The Inspectorate said it will use this metric to direct regulatory resource and to hold companies publicly accountable for delivery.