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UK tap water: hardness, safety and hosepipe bans by postcode

16 regional water companies supply drinking water across England and Wales, and the quality of that water is regulated by the Drinking Water Inspectorate in England and Wales, per the water industry's own Water Company Boundaries layer (UC2) (19 September 2026, read 20 September 2026).

Source: the water industry's own Water Company Boundaries layer (UC2) — dated 19 September 2026, read 20 September 2026Water company boundaries © Water UK, licensed under CC BY 4.0

Drinking Water Inspectorate (DWI) enforces the UK drinking water quality regulations in England and Wales. Figures it classifies or regulates on this page cover England and Wales only.

What this part of the site is

This section publishes what can be read about drinking water in this country from the organisations that produce it: the companies that supply the water, and the regulator that oversees them. It is a record of published documents rather than a laboratory of our own, and it is written for a reader who wants to see the document a figure came out of.

Every page here prints its source and the day that source was read. Where a company publishes nothing that can be read in bulk, the page says so in those words instead of filling the space with something that reads better.

Where these figures come from

Water here is supplied by regional companies, and in some parts of the country by a single national undertaker. Each publishes its own reports, on its own schedule and in its own format, and there is no national dataset behind them that anyone can download.

The regulator publishes the rules, and the scale that water is described against. It does not publish the measurements. So a figure on these pages is a water company's own figure, quoted with the document it came from, and the band beside it is the regulator's word rather than ours.

Why the coverage is uneven, and why it is left that way

What this site holds follows what each company chooses to publish, not where people live. A company that publishes its supply zones as a list can be read in full. A company that hands out a figure only after an address is typed cannot be read at all without interrogating its website one address at a time, which is not something this site does to somebody else's server.

The tables below therefore look lopsided, and that is the measurement rather than a gap in the work. Filling it in would replace something true and partial with something complete and invented, and the page would give no sign of the difference.

What you will not find here

No figure on these pages is estimated, averaged across areas that were measured separately, or carried across from a neighbouring area. Where more than one measured value applies to a place, the page prints the range and names what it varies by.

Nor is anything here a verdict of ours on whether water is fit to drink. That judgement belongs to the regulator, against standards it publishes itself, and a page claiming otherwise would be inventing an authority it does not have.

What we hold for the United Kingdom

Who regulates this water

Drinking Water Inspectorate (DWI) enforces the UK drinking water quality regulations in England and Wales. Where a figure on these pages is classified, it is classified against that regulator’s own published tables rather than a scale of ours.

Drinking Water Inspectorate

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By TapWaterData Editorial