Photo credit: Swanky Fella

Drinking water quality in England remained exceptionally high in 2025, even as ageing infrastructure and deteriorating asset health emerged as a threat to the long-term resilience of supplies. The Drinking Water Inspectorate’s Chief Inspector’s Annual Report found that 99.97 per cent of more than 3.5 million regulatory tests met the required standards.

Ageing assets the biggest risk

The report identifies ageing assets as one of the industry’s largest risks. During 2025, the DWI recorded 47 drinking water quality events linked directly to poor asset health or treatment plant failures, including structural defects at treatment works and treated water storage facilities. The regulator said water entering service reservoirs and treated water tanks remains a recurring and preventable cause of incidents, underlining the need for robust maintenance and asset renewal.

Chief Inspector Marcus Rink said consumers could continue to have confidence in the safety of their water, which he ranked among the best anywhere, but warned that holding those standards would demand sustained investment, innovation and effective regulation. Resilient supply, he said, is becoming a pressing matter of public concern given its bearing on communities and the economy.

Incidents and compliance

A total of 586 drinking water quality events were reported to the DWI during the year. There were no major incidents, though seven were classified as serious and 168 as significant. The industry’s Compliance Risk Index, which measures the risk posed by regulatory failures, improved to 2.702 compared with 2024.

The Inspectorate expanded its monitoring of emerging contaminants, carrying out more than 635,000 analyses for PFAS during 2025. Only two results exceeded the DWI’s guidance value of 0.1 micrograms per litre, both at the same Southern Water site, where operational measures kept the water supplied to customers below the threshold.

Tougher oversight

Regulatory scrutiny intensified over the year, with the DWI completing 39 audits, issuing 205 recommendations and serving 109 enforcement notices. The report introduces a new Enforcement Performance Metric intended to assess how effectively companies deliver regulatory improvements. Rink said it was vital that, as the government takes forward wider reforms through the Clean Water Bill and plans for a single regulator, the focus remained on protecting public health and maintaining the standards consumers expect.