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Polluted by sewage 7,592 hours in 2025
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We get information about overflowing CSOs since January 2025. Here is a chart of the last three months of data for Caerphilly, here you can see overflows in red, the darker the red, the more the CSO overflowed that day.
Each CSO has a row, the most recent data is on the right hand side.
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Donate Now| Company | Site Name | Receiving Waterway | Overflow Days | Total Duration (hours) | Total Duration (days) |
|---|---|---|---|---|---|
| Dwr Cymru Welsh Water | Bedwas Road Storm Overflow | Porset Brook | 99 | 1,081 h 3m | 45.04 |
| Dwr Cymru Welsh Water | Glan-yr-Afon Lane 2 Storm Overflow | River Rhymney | 92 | 1,064 h 39m | 44.33 |
| Dwr Cymru Welsh Water | Pontllanfraith Gelligroes Mill Road Storm Overflow | Sirhowy River | 93 | 917 h 59m | 38.21 |
| Dwr Cymru Welsh Water | Cwm Las Storm Overflow | River Rhymni | 72 | 805 h 22m | 33.54 |
| Dwr Cymru Welsh Water | Caerphilly Bypass Supermarket Storm Overflow | Nant Yr Aber | 38 | 476 h 14m | 19.83 |
| Dwr Cymru Welsh Water | Twyn Road Ystrad Mynach Storm Overflow | River Rhymni | 59 | 474 h 57m | 19.75 |
| Dwr Cymru Welsh Water | Springfield Estate Storm Overflow | River Sirhowy | 61 | 438 h 47m | 18.25 |
| Dwr Cymru Welsh Water | Bryn Siriol Storm Overflow | Nant Yr Aber | 43 | 384 h 30m | 16 |
| Dwr Cymru Welsh Water | A472 Maesycwmmer Storm Overflow | River Rhymni | 54 | 286 h 42m | 11.92 |
| Dwr Cymru Welsh Water | Oaks End Close Footbridge Storm Overflow | Nant Cylla | 65 | 237 h 41m | 9.88 |
| Dwr Cymru Welsh Water | River Terrace Pengham Storm Overflow | River Rhymney | 35 | 196 h 45m | 8.17 |
| Dwr Cymru Welsh Water | Ford Road Pengam Storm Overflow | River Rhymni | 47 | 179 h 15m | 7.46 |
| Dwr Cymru Welsh Water | Pentwyngwyn Road Storm Overflow | River Rhymney | 40 | 159 h 18m | 6.62 |
| Dwr Cymru Welsh Water | William Street Tir-y-berth Storm Overflow | River Rhymney | 42 | 150 h 33m | 6.25 |
| Dwr Cymru Welsh Water | South of Nine Mile Point Road Wattsville Storm Overflow | Sirhowy River | 25 | 111 h 1m | 4.62 |
| Dwr Cymru Welsh Water | Gelligroes Roundabout A472 Storm Overflow | Sirhowy River | 61 | 104 h 52m | 4.33 |
| Dwr Cymru Welsh Water | Trelyn Lane Storm Overflow | River Rhymni | 27 | 99 h 51m | 4.12 |
| Dwr Cymru Welsh Water | Pontllanfraith Tram Road Storm Overflow | Sirhowy River | 25 | 89 h 15m | 3.71 |
| Dwr Cymru Welsh Water | Ystrad Mynach Bridge Storm Overflow | River Rhymney | 23 | 76 h 45m | 3.17 |
| Dwr Cymru Welsh Water | Wyllie Halt Storm Overflow | Sirhowy River | 18 | 66 h 40m | 2.75 |
| Dwr Cymru Welsh Water | Pant Glas Industrial Estate Storm Overflow | River Rhymney | 15 | 57 h 15m | 2.38 |
| Dwr Cymru Welsh Water | Woodland Place Storm Overflow | River Rhymney | 23 | 38 h 56m | 1.58 |
| Dwr Cymru Welsh Water | High Street Gant-y-nant Storm Overflow | River Rhymni | 8 | 18 h 48m | 0.75 |
| Dwr Cymru Welsh Water | Nine Mile Point Storm Overflow | River Sirhowy | 8 | 17 h 8m | 0.71 |
| Dwr Cymru Welsh Water | Graig-Y-Fedw Storm Overflow | Nant Yr Aber | 7 | 15 h 19m | 0.62 |
| Dwr Cymru Welsh Water | Commercial Street Senghenydd Storm Overflow | Nant Cwm-Parc | 10 | 7 h 56m | 0.29 |
| Dwr Cymru Welsh Water | Coopers Court Storm Overflow | River Rhymni | 9 | 5 h 46m | 0.21 |
| Dwr Cymru Welsh Water | Windsor Place Storm Overflow | Nant Yr Aber | 5 | 5 h 43m | 0.21 |
| Dwr Cymru Welsh Water | Forge Road Machen Overflow | River Rhymni | 4 | 4 h 30m | 0.17 |
| Dwr Cymru Welsh Water | Senghenydd Storm Overflow | Nant Yr Aber | 3 | 4 h | 0.17 |
| Dwr Cymru Welsh Water | Glan-y-nant Riverside Path Storm Overflow | River Rhymni | 3 | 3 h 36m | 0.12 |
| Dwr Cymru Welsh Water | Forge Road Storm Overflow | River Rhymni | 6 | 3 h 10m | 0.12 |
| Dwr Cymru Welsh Water | Riverside Park Trethomas Storm Overflow | River Rhymney | 6 | 2 h 37m | 0.08 |
| Dwr Cymru Welsh Water | Islwyn Road Storm Overflow | Sirhowy River | 3 | 1 h 14m | 0.04 |
| Dwr Cymru Welsh Water | New Road Roundabout Storm Overflow | River Rhymni | 1 | 0 h 59m | 0 |
| Dwr Cymru Welsh Water | Nantgawr Road Storm Overflow | Nant-yr-Aber | 1 | 0 h 59m | 0 |
| Dwr Cymru Welsh Water | Trelyn Park Storm Overflow | River Rhymney | 2 | 0 h 41m | 0 |
| Dwr Cymru Welsh Water | Railway Cottages Storm Overflow | Sirhowy River | 1 | 0 h 28m | 0 |
| Dwr Cymru Welsh Water | Main Road Maesycwmmer Overflow | Rhymney River | 1 | 0 h 17m | 0 |
| Dwr Cymru Welsh Water | Coedcae Road Abertridwr Storm Overflow | Nant Yr Aber | 1 | 0 h 15m | 0 |
| Dwr Cymru Welsh Water | William Street Fleur-de-lis Storm Overflow | River Rhymney | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Church Street Ystrad Mynach Overflow | River Rhymni | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Church Street Rear Ystrad Mynnach Storm Overflow | Nant Caeach | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Victoria Road Fleur-De-Lis Storm Overflow | River Rhymni | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Greenway Bedwas Storm Overflow | River Rhymni | 0 | 0 h | 0 |
EDM (Event Duration Monitoring) data and Consented Discharges to Controlled Waters with Conditions from Environment Agency & Data Map Wales, and Scottish Water
Experimental derived data from Thames Water API, Some data may be missing or inaccurate. Live sewage data from Stream Water API
Uses Environment Agency rainfall data from the real-time data API (Beta) - Rainfall data is delayed by up to two days.
This website is intended to provide an accurate representation of the Environment Agency data. The data is hard to use, and thus some errors may have been made. If you find something that is incorrect, please raise an issue at the GitHub issues page and we'll endeavour to fix it quickly.
This project is not associated, approved or endorsed by any of the companies whose logos you see here.
Get in touch if you have queries or want to discuss our data.
press [at] top-of-the-poops.org