PFAS in UK tap water: what is monitored and where results are published

What PFAS are

PFAS (per- and polyfluoroalkyl substances) are a large group of man-made chemicals. DWI lists uses including non-stick pans, outdoor clothing, food packaging and firefighting foam. They are very resistant to breaking down, which is why they are called forever chemicals, and they can reach rivers and groundwater that are used as drinking-water sources.

England and Wales: DWI guidance, no legal limit yet

The Drinking Water Inspectorate (DWI) says there are currently no statutory standards for PFAS in drinking water in England and Wales. Instead, it has issued guidance that water companies must follow. Companies assess the risk at each water source and test for a list of 48 named PFAS.

DWI’s guidance (version 1.1, March 2025) puts sites into three tiers based on PFAS concentrations:

• Tier 1: below 0.01 µg/l (micrograms per litre). Regular monitoring and risk assessment.
• Tier 2: below 0.1 µg/l. More frequent monitoring and a strategy to progressively reduce PFAS concentrations.
• Tier 3: 0.1 µg/l or more. In water supplied to consumers, companies must notify DWI and the health authorities, and put in place measures to bring concentrations below 0.1 µg/l.

The tiers apply to individual PFAS. From 1 January 2025 companies must also report a combined “sum of PFAS” result, and sites can be placed in a tier on that basis too. DWI’s consumer page describes the guideline value as 0.1 µg/l for the sum of 48 named PFAS.

In its PFAS plan, updated in August 2026, the UK Government said it will consult on introducing a statutory PFAS standard for drinking water in England. We did not find that a consultation had started by the review date.

Scotland: a legal limit

Since 1 January 2023, the Public Water Supplies (Scotland) Regulations 2014 have included a legal limit of 0.1 µg/l for the sum of PFAS. The Drinking Water Quality Regulator for Scotland (DWQR) oversees Scottish Water’s monitoring and publishes the results in its annual report.

Where PFAS results are published

• England: DWI’s Drinking Water 2025 report, PFAS section. DWI reports that companies in England and Wales carried out more than 666,000 analyses for individual PFAS in 2025. For individual PFAS, it reports two treated-water samples supplied to consumers in Tier 3, both from one Southern Water treatment works. It also reports sum-of-PFAS calculations in Tier 3 and describes sum-of-PFAS events, including 0.103 µg/l at Wessex Water’s Charlton Minety works (February 2025) and 0.106 µg/l at Hanningfield treatment works (October 2025). Read the report for the full tables and the companies’ actions.
• Wales: DWI’s Drinking Water 2025 report for Wales, PFAS section.
• Scotland: DWQR’s Drinking Water Quality in Scotland 2025 report, which includes Scottish Water’s sum-of-PFAS testing results.
• Your supplier: ask your water company about PFAS monitoring for the sources that supply you. We did not find a single national table of PFAS results by supplier or area. PFAS monitoring is focused on water sources and treatment works, not individual homes.

Asking about your area

Your water supplier can tell you which treatment works or sources supply your address and what PFAS monitoring it does there. For a private well or borehole, contact your local council, which is responsible for private water supplies (in Northern Ireland, the Drinking Water Inspectorate for Northern Ireland). Do not use a PFAS result from another area as a guide to yours.

WaterGrade shows other published results, such as lead, nitrate and fluoride, for some places. See what is in UK tap water or look up the published results for your postcode.