Is tap water safe to drink in the UK and London? What the published results show

What the drinking-water regulators report

• England, 2025: the Drinking Water Inspectorate reports overall compliance with drinking-water standards of 99.97% (chemical parameters 99.95%, microbiological parameters 99.98%). Drinking water 2025 (England): compliance with water quality standards.
• Scotland, 2025: the Drinking Water Quality Regulator for Scotland reports that 99.88% of 137,947 regulatory tests on samples from consumers’ taps met the required standards, a slight reduction compared with 2024. Drinking water in Scotland 2025 (announcement of the regulator’s annual report).

Wales and Northern Ireland have their own annual reports: the Drinking Water Inspectorate publishes a separate report for Wales, and the Drinking Water Inspectorate for Northern Ireland publishes an annual report on drinking water quality in Northern Ireland. We have not quoted their figures here because we could not verify them on the review date.

These national figures describe all the samples taken across a nation in that year. They do not describe any particular town, street or home.

Can you drink tap water in London?

London is supplied by several water companies, including Thames Water, Affinity Water and SES Water. The Drinking Water Inspectorate regulates them, and each publishes water-quality results for its supply zones. The England figure above covers London along with the rest of England; the regulator does not publish a single London figure on the page we cite. WaterGrade shows published results for many London places supplied by Thames Water and Affinity Water. London water is often hard; hardness affects limescale, not whether water meets drinking-water standards.

See the published results WaterGrade holds for London or look up the published results for your postcode.

What local published results show

Water suppliers publish results for each water supply zone, usually once a year or as a rolling 12-month summary. For each substance they typically show the legal limit, the number of samples, an average and a range, and how many samples did not meet the standard. WaterGrade shows these results for the places and suppliers we cover, with the reporting period and units, and highlights where a supplier reported that samples did not meet a standard.

What each substance is and its legal limit

What published results cannot show

• Your own tap. Results summarise samples across a supply zone. They are not a test of the water in your home.
• Your pipes. Lead and some other metals mostly come from pipes and fittings inside properties. An area average cannot rule out lead from your own pipes. How to check for lead pipes.
• Today. An annual or rolling summary describes past samples. It cannot tell you about a burst main, an incident or a change happening now.
• Every sample. An average below the limit does not show that every sample met the standard.
• Everywhere. WaterGrade holds results for some suppliers and places only. Where we hold no result, that is unknown, not good or bad. We hold no PFAS results; see where PFAS monitoring is published.

When to contact your water supplier

• Your water suddenly changes colour, becomes cloudy or tastes or smells different.
• You think you have lead pipes, or you want your water tested.
• You have received a notice, or want to check whether a notice applies to your address.

Always follow a boil-water or do-not-drink notice from your supplier. If you feel unwell, contact NHS 111 or your GP. The regulators also explain how to raise a concern: DWI advice for consumers.

Tap water and baby formula

The NHS advises using freshly boiled tap water to make up formula, left to cool for no more than 30 minutes so that it stays at a temperature of at least 70°C. It says not to use artificially softened water or water that has been boiled before. The NHS says bottled water is not usually recommended for formula because it is not sterile and may contain too much sodium or sulphate.

NHS: how to make up baby formula

Private water supplies

If your home gets water from a private well, borehole or spring, the results suppliers publish do not apply to it. Private supplies are regulated by the local council (in Northern Ireland, by the Drinking Water Inspectorate for Northern Ireland). Who to contact about testing.