Water company · 2025
Dwr Cymru Welsh Water's sewage record
96,054 discharges from 2,244 monitored storm overflows in 2025, for 779,874 hours in total. These are the Environment Agency's published figures.
96,054discharges
779,874hours
146monitors working under 90% of the year
The ten worst overflows
| Overflow | Into | Constituency | Discharges | Hours |
|---|---|---|---|---|
| Llanfachraeth WwTW | Mawddach - Lower | Dwyfor Meirionnydd | 366 | 5,498 |
| Cwrtnewydd Wastewater Treatment Works | Cledlyn - Headwaters to Confluence With Teifi | Ceredigion Preseli | 363 | 4,409 |
| Connahs Quay Syphons to STW | — | Alyn and Deeside | 318 | 2,369 |
| Waterston WwTW Inlet CSO | — | Mid and South Pembrokeshire | 314 | 2,307 |
| Llan Ffestiniog Wastewater Treatment Works | Cynfal | Dwyfor Meirionnydd | 306 | 3,181 |
| Cwm Penmachno WwTW Settled Storm | Machno | Bangor Aberconwy | 300 | 6,880 |
| Efailnewydd Wastewater Treatment Works | Rhyd-Hir | Dwyfor Meirionnydd | 281 | 1,145 |
| Pentre-Cwrt Wastewater Treatment Works | Teifi - Afon Clettwr to Afon Ceri | Caerfyrddin | 275 | 2,280 |
| Llanaelhaearn STW | — | Dwyfor Meirionnydd | 259 | 2,409 |
| Capel Curig Wastewater Treatment Works | Llugwy - Conwy to Nantygwryd | Bangor Aberconwy | 243 | 3,034 |
The constituencies it affects most
- Dwyfor Meirionnydd — 11,749 discharges from 194 overflows
- Caerfyrddin — 9,714 discharges from 129 overflows
- Ceredigion Preseli — 8,345 discharges from 134 overflows
- Mid and South Pembrokeshire — 5,941 discharges from 110 overflows
- Brecon, Radnor and Cwm Tawe — 5,206 discharges from 111 overflows
- Rhondda and Ogmore — 5,035 discharges from 112 overflows
- Bangor Aberconwy — 4,239 discharges from 85 overflows
- Ynys Môn — 3,527 discharges from 78 overflows
- Llanelli — 3,402 discharges from 83 overflows
- Neath and Swansea East — 3,228 discharges from 73 overflows
If you are a Dwr Cymru Welsh Water customer, you cannot switch supplier, but you can claim compensation when they miss a legal standard. What you are owed →
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