As of Ofwat APR 2024-25 / DWI 2024: Portsmouth Water has the fewest supply interruptions β customers lost an average of only 00:02:01 of water supply per property (for interruptions lasting 3+ hours), vs the England and Wales average of 22 mins. Southern Water and DΕ΅r Cymru Welsh Water had over 2 hours of average lost supply. Source: Ofwat APR 2024-25 via DiscoverWater.co.uk (OGL v3.0).
| Rank (fewest first) | Company | Avg interruptions | GWSS |
|---|---|---|---|
| #1 | Portsmouth Water | 00:02:01 | 88.9/100 |
| #2 | Affinity Water | 00:03:21 | 84/100 |
| #3 | Severn Trent Water | 00:04:34 | 58.2/100 |
| #4 | Essex and Suffolk Water | 00:04:40 | 69.4/100 |
| #5 | Northumbrian Water | 00:04:40 | 58/100 |
| #6 | Bristol Water | 00:06:49 | 89.7/100 |
| #7 | Anglian Water | 00:06:51 | 87.1/100 |
| #8 | Yorkshire Water | 00:08:27 | 70.8/100 |
| #9 | Thames Water | 00:09:35 | 62.7/100 |
| #10 | Wessex Water | 00:10:00 | 77.9/100 |
| #11 | Hafren Dyfrdwy | 00:11:11 | 64.2/100 |
| #12 | United Utilities | 00:14:17 | 48.2/100 |
| #13 | South West Water | 00:14:44 | 79.5/100 |
| #14 | Cambridge Water | 00:15:04 | 73.1/100 |
| #15 | South Staffs Water | 00:15:04 | 64.3/100 |
| #16 | SES Water | 00:26:40 | 93.2/100 |
| #17 | South East Water | 00:44:06 | 75.8/100 |
| #18 | DΕ΅r Cymru Welsh Water | 02:17:44 | 19.4/100 |
| #19 | Southern Water | 02:21:50 | 50/100 |
Source: Ofwat APR 2024-25, accessed via DiscoverWater.co.uk (CSV: 2025-Avg-minutes-lost-Current-UK.csv). Average minutes per property for supply interruptions lasting β₯3 hours. Open Government Licence v3.0. GWSS methodology.