1 2 works hold more than one permit; each permit is a dot, so the map shows 5,904 dots for 5,902 works, on 10 company maps.
Dŵr Cymru’s map holds its 687 works in Wales as well as its works in England.
Not tested. A layer shows a company as not tested when our test could not be run for it because a source is not held (for example, no daily flow data), or when the test is not on its map. It is not a zero.
What this page is. An overview of the ten sewerage company maps. Clicking a company opens its own map, unchanged; figures come from the public sources listed in each card's documents. Counts here are the counts of works on each company's map, for the same test; a works with two permits shows as two dots.
Works. Locations, names and permits from the Environment Agency's public registers (Open Government Licence), as on each company map.
Company areas. Ofwat, sewerage services areas, version 1_5 (republished on Water UK's Stream portal), published under the Open Government Licence. This shapefile has been digitised from the legal records by the Water Services Regulation Authority (Ofwat) with support from Ordnance Survey. This shapefile is designed for geospatial analysis only. The definitive legal record of areas remains the maps and other information set out in the appointments of companies as water and/or sewerage undertakers and subsequent area variations. This shapefile does not include information on any premises or installations that are located outside the boundary but included in the area or that are located inside the boundary but excluded from the area. For the purposes of geospatial analysis and visual display the Mean High Water Line has been used for any seaward boundary (although the low water mark is more likely to be the actual boundary) and islands that are part of the area may have been omitted. Lines are simplified for display (about 400 m), and islands smaller than about half a square kilometre are left out. Small inset areas served by new-entrant companies (NAVs) are not drawn. 228 of the 5,904 dots (3.9%) fall outside their company's drawn area: most are coastal and estuary outfalls beyond the coastline (on the v1.2 page, 177 of 5,217, five lay just across a border between companies and two South West Water locations appeared misplaced).
Not mapped. Hafren Dyfrdwy's works: a separate sewerage licence in the Severn Trent group.
Wales. Dŵr Cymru's works in Wales come from Natural Resources Wales permits; their cards carry fewer figures (see that map).
Company maps used. Anglian Water: map v2.25 (11 Nov 2026); Dŵr Cymru Welsh Water: map v2.25 (11 Nov 2026); Northumbrian Water: map v2.25 (11 Nov 2026); Severn Trent Water: map v2.25 (11 Nov 2026); South West Water: map v2.25 (11 Nov 2026); Southern Water: map v2.25 (11 Nov 2026); Thames Water: map v2.25 (11 Nov 2026); United Utilities: map v2.25 (11 Nov 2026); Wessex Water: map v2.25 (11 Nov 2026); Yorkshire Water: map v2.25 (11 Nov 2026).