WaterGrade open data
Two downloads: Northern Ireland Water’s annual hardness by supply zone for 2023–2025, and our register of where UK water quality and hardness data is published. We only include measurement values whose licence allows reuse.
Version 1.0.0 · updated 11 September 2026
Not a safety dataset. Hardness describes limescale potential, not whether water is safe. Each value summarises samples across a supply zone for one year. It is not a test at any address and says nothing about current incidents. There are no postcodes in these files. To check the water at your home, look up your postcode.
1. NI Water hardness by supply zone, 2023–2025
740 values from 185 annual zone reports covering 66 NI Water supply zones. Each report gives total hardness (mg/l as CaCO₃), calcium, magnesium and potassium, with the number of samples. Zone names and codes are as NI Water published them for each year.
Licence: the values are NI Water data published on OpenDataNI under the Open Government Licence v3.0. Please include: “Contains public sector information licensed under the Open Government Licence v3.0. Source: Northern Ireland Water, water hardness by water supply zone, published on OpenDataNI.” WaterGrade’s identifiers and columns are CC BY 4.0.
Provenance
WaterGrade read NI Water’s three annual PDF tables, Water Hardness by Water Supply Zone, from the OpenDataNI dataset. Our importer checks the zone count for each year, the column units and the arithmetic between columns before a report is approved. Each row gives the source URL and the file’s SHA-256 fingerprint. On 11 September 2026 the live files still matched those fingerprints.
| Year | Source file | Retrieved |
|---|---|---|
| 2023 | 2023 water hardness by supply zone (PDF) | 6 September 2026 |
| 2024 | 2024 water hardness by supply zone (PDF) | 6 September 2026 |
| 2025 | 2025 water hardness by supply zone (PDF) | 6 September 2026 |
Not included: NI Water’s postcode-to-zone lookup (it changes by year and some postcodes match more than one zone or none; use NI Water’s own lookup), the customer-tap results and the full quality registers. A missing substance is not zero. NI Water uses extra soft-water categories; WaterGrade describes hardness with the DWI bands.
2. UK water-data source register
24 regulators, open-data portals and water suppliers, with official lookup URLs, what each publishes, reporting periods and hardness units where we have reviewed them, and how many approved reports WaterGrade holds. It contains links and descriptions only, no measurement values. The same list is on our guide Where UK water quality and hardness data is published.
Licence: CC BY 4.0. Please credit “WaterGrade (watergrade.co.uk/open-data)”. The pages it links to remain under their owners’ terms. The JSON file also contains our licence register.
What is left out, and why
WaterGrade shows results from other suppliers on its report pages, but we only republish values in bulk when the source licence allows it. We checked each source on 11 September 2026:
| Source | Reuse terms found | Values in dataset |
|---|---|---|
| Northern Ireland Water via OpenDataNI | Open Government Licence v3.0 | Yes |
| Drinking Water Inspectorate (England and Wales) | Open Government Licence v3.0 (except where otherwise stated) | No |
| Drinking Water Quality Regulator for Scotland | Open Government Licence (logos excluded) | No |
| Drinking Water Inspectorate for Northern Ireland (DAERA) | Not confirmed | No |
| Thames Water | Restricted: written consent needed | No |
| Scottish Water | Not confirmed | No |
| Affinity Water | Not confirmed | No |
| Yorkshire Water | Not confirmed | No |
| Severn Trent Water | Not confirmed | No |
| United Utilities | Not confirmed | No |
| Wessex Water | Not confirmed | No |
| Other UK water suppliers listed in the source register | Not confirmed | No |
| Stream (water industry open-data portal) | Not confirmed | No |
| postcodes.io / ONS Postcode Directory | Not confirmed | No |
This is a record of what we found, not legal advice. If you publish water data, check each source’s terms yourself.
Fields
NI Water hardness file (21 columns)
record_id— WaterGrade identifier for this value; it changes if NI Water replaces that year’s source filesuppliersupply_zone_code— NI Water zone code, e.g. ZN0102supply_zone_name— Zone name as published for that yeargeography_typeperiod_label— Calendar year of the source tableperiod_startperiod_endparameter— Total hardness, calcium, magnesium or potassiumvalue— Number as extracted from the source table (trailing zeros are not kept)qualifier— “=” for every row in this releaseunit— Unit as published (total hardness in mg/l as CaCO₃)sample_count— Number of samples behind the figure, as publishedsource_titlesource_urlsource_sha256— SHA-256 of the source PDF WaterGrade readsource_retrieved_atsource_licence— Licence of the value (OGL-UK-3.0)source_licence_urlattributionwatergrade_report_id— Approved WaterGrade report the value comes from
Source register (21 columns)
register_idorganisationrolenationregionpublishesofficial_urladditional_urladditional_url_labelhow_to_findgeographyreporting_periodhardness_unit_as_publishedwatergrade_pagewatergrade_approved_reports— approved reports WaterGrade holds, all editionswatergrade_periods_heldlicence_statuslicencelicence_record_idmeasurement_values_in_this_dataset— “yes” only where the licence allows reusechecked_on
Files are UTF-8. CSV follows RFC 4180. Licence and attribution text · Manifest with file fingerprints
Updates and changes
- Version 1.0.0, 11 September 2026: First release: NI Water annual hardness and minerals by supply zone, 2023–2025, and WaterGrade's source register.
We plan to update the files when NI Water publishes a new annual hardness table, and to add other suppliers only after their licence allows reuse. Found a problem? Tell us.
What WaterGrade covers · Sources and methodology · Hardness converter