Where does the data come from?

Drinking-water test results that water companies publish through the Stream Water Data Portal, Environment Agency river and groundwater monitoring, and water company incident feeds. Every report carries its source, sample count and last sample date, and links to a public page showing the same figures.

How much of the UK is covered?

Scored reports exist for over 2,200 postcode districts, which is most of England, Wales and Northern Ireland. Hardness readings cover around 1,000 districts, with a postcode-area estimate for the rest and a flag telling you which is which.

How often is it updated?

Test results refresh as water companies publish them, typically monthly. Incidents refresh every fifteen minutes. PFAS monitoring refreshes weekly.

Is this address-level or postcode-level?

Reports are per postcode district, the outward half of the postcode, which is the level at which water companies report supply zones. Send a full postcode and we resolve it for you.

Do I have to credit TapWater.uk?

On the free pilot, yes: a 'Data: TapWater.uk' line with a link. On paid plans attribution is optional.

Water data for every UK address

The report behind 2,124 postcode pages on this site, as JSON. Quality score, hardness, flagged readings, PFAS and live incidents for any postcode, from the same published tests the water companies file. One call per address.

Request a pilot key See a report

Who it is for

Property portals and letting agents

A water line on every listing: hardness, score and supplier next to the EPC. Tenants ask about limescale and drinking water; the answer is one field.

Conveyancers and home-buyer reports

A water section in the report pack, from the same public tests the water company files, with a link the buyer can check themselves.

Water treatment installers and filter brands

Qualify a lead before the survey. Hardness and flagged readings for the customer's postcode, in your CRM, at the moment they enquire.

Insurers, boiler cover and appliance brands

Scale risk by address. Very hard water shortens boiler and appliance life measurably; price and advise accordingly.

What a report looks like

A real response for a Bedfordshire postcode. Every number on it also appears on the public page at tapwater.uk/postcode/LU5, so your users, and you, can check it.

{
  "postcode": "LU5 2AB",
  "district": "LU5",
  "areaName": "Central Bedfordshire",
  "supplier": { "name": "Thames Water", "id": "thames-water" },
  "score": 8.4,
  "grade": "good",
  "hardness": { "mgPerLitre": 289, "label": "very hard", "estimated": false },
  "contaminants": {
    "tested": 23,
    "flagged": 1,
    "flaggedReadings": [
      { "name": "Nitrite", "value": 0.67, "unit": "mg/L", "ukLimit": 0.5, "status": "fail" }
    ]
  },
  "pfas": { "inTapWaterTests": null, "nearbyMonitoring": null },
  "incidents": [],
  "provenance": {
    "dataSource": "stream",
    "sampleCount": 73,
    "lastSampleDate": "2025-12-31",
    "reportUrl": "https://www.tapwater.uk/postcode/LU5"
  }
}

The call

GET /api/v1/report?postcode=LU5 2AB
x-api-key: tw_live_…

Also in the response

PFAS found in tap-water tests and in river and groundwater monitoring within 10 km. Any live supply incident affecting the district. Sample count, date range and source, so you can show provenance.

Quota headers

Every response carries your monthly limit and what is left. No surprise invoices.

Pricing

Pilot

Free90 days

1,000 lookups a month

Full report API. Attribution required. For evaluating against your own addresses.

Start with this

Starter

£99a month

5,000 lookups a month

Report API and embeddable widget. Email support. Attribution optional.

Growth

£249a month

50,000 lookups a month

Everything in Starter, plus a monthly bulk CSV of every district for offline use.

Enterprise

Custom

Unlimited

Bulk delivery, custom fields, uptime commitment, invoicing. For portals and report providers at scale.

A lookup is one successful report. Errors and repeated lookups of the same postcode within a day are not counted. The embeddable widget stays free for any site that keeps the attribution link.

Questions

Where does the data come from?: Drinking-water test results that water companies publish through the Stream Water Data Portal, Environment Agency river and groundwater monitoring, and water company incident feeds. Every report carries its source, sample count and last sample date, and links to a public page showing the same figures.
How much of the UK is covered?: Scored reports exist for over 2,200 postcode districts, which is most of England, Wales and Northern Ireland. Hardness readings cover around 1,000 districts, with a postcode-area estimate for the rest and a flag telling you which is which.
How often is it updated?: Test results refresh as water companies publish them, typically monthly. Incidents refresh every fifteen minutes. PFAS monitoring refreshes weekly.
Is this address-level or postcode-level?: Reports are per postcode district, the outward half of the postcode, which is the level at which water companies report supply zones. Send a full postcode and we resolve it for you.
Do I have to credit TapWater.uk?: On the free pilot, yes: a 'Data: TapWater.uk' line with a link. On paid plans attribution is optional.

Request a pilot key

Ninety days, a thousand lookups a month, no card. Tell us what you are building and we send a key within one working day. Or email hello@tapwater.uk.