Merthyr Tydfil and Aberdare - 2025 Sewage

Polluted by sewage 15,242 hours in 2025 - That's 1.76 years

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Contains OS Data © Crown copyright & database right 2021-2024
© Top of the Poops 2021-2024

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You're looking at the totals that we have calculated for sewage in Merthyr Tydfil and Aberdare for 2025. It is an estimate, based on very poor quality live data from the Water Companies. This may not align with the 'official' reported sewage values from the water companies, which is reported in April following then end of the year - so 2025 numbers are reported in April 2026.

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Constituencies near Merthyr Tydfil and Aberdare

Daily Data

We get information about overflowing CSOs since January 2025. Here is a chart of the last three months of data for Merthyr Tydfil and Aberdare, 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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Daily data is experimental and data is not guaranteed to be accurate. Please inform us of any issue, we will fix.
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Totals so far

Company Site Name Receiving Waterway Overflow Days Total Duration (hours) Total Duration (days)
Dwr Cymru Welsh Water Hirwaun Industrial Estate WwTW Storm Overflow Afon Camnant 133 2,853 h 45m 118.88
Dwr Cymru Welsh Water Mikes Field Storm Overflow River Cynon 104 1,408 h 30m 58.67
Dwr Cymru Welsh Water Pontsticill WwTW Storm Overflow River Taff 72 1,170 h 31m 48.75
Dwr Cymru Welsh Water Aberaman Park West Storm Overflow River Cynon 101 1,125 h 45m 46.88
Dwr Cymru Welsh Water East of Rounabout A4102 jct with High Street Storm Overflow Morlais Brook 99 652 h 57m 27.17
Dwr Cymru Welsh Water Cilmery WwTW Storm Overflow Afon Chwefri 64 583 h 45m 24.29
Dwr Cymru Welsh Water Pontbren Storm Overflow River Cynon 69 582 h 54m 24.25
Dwr Cymru Welsh Water Pontrhun Bridge Storm Overflow River Taff 80 515 h 21.46
Dwr Cymru Welsh Water Oakland Street Bedlinog Storm Overflow River Taff 58 495 h 50m 20.62
Dwr Cymru Welsh Water Meirion Street Roundabout Trecynon Storm Overflow River Cynon 80 471 h 30m 19.62
Dwr Cymru Welsh Water Pant-Y-Cerdin Storm Overflow Aberdare Canal 82 418 h 51m 17.42
Dwr Cymru Welsh Water Merthyr Road Bridge Storm Overflow River Cynon 68 389 h 8m 16.21
Dwr Cymru Welsh Water Monk Street No1 Storm Overflow River Cynon 75 381 h 15m 15.88
Dwr Cymru Welsh Water Gellifaelog Old Road Storm Overflow Morlais Brook 47 344 h 31m 14.33
Dwr Cymru Welsh Water Maes Y Ffion Storm Overflow Nant-Y-Derlwyn 57 332 h 39m 13.83
Dwr Cymru Welsh Water Trelewis Glynbargoed Road Storm Overflow Pandy Brook 77 276 h 53m 11.5
Dwr Cymru Welsh Water Merthyr Tydfil Industrial Park Storm Overflow Pentrebach Brook 56 257 h 22m 10.71
Dwr Cymru Welsh Water Dare Road Storm Overflow River Dare 37 245 h 33m 10.21
Dwr Cymru Welsh Water Station Street Aberdare Storm Overflow River Cynon 65 237 h 9.88
Dwr Cymru Welsh Water Merthyr Tydfil College Car Park Storm Overflow River Taff 50 217 h 30m 9.04
Dwr Cymru Welsh Water Bethesda Street Merthyr Tydfil Storm Overflow River Taff 64 198 h 15m 8.25
Dwr Cymru Welsh Water Bro Deg 2 Storm Overflow River Cynon 50 187 h 37m 7.79
Dwr Cymru Welsh Water Gladstone Street Storm Overflow Tributary of Afon Aman 21 151 h 1m 6.29
Dwr Cymru Welsh Water Tan Y Bryn Gardens Llwydcoed Overflow River Cynon 40 132 h 59m 5.5
Dwr Cymru Welsh Water Fiddlers Elbow Quakers Yard Storm Overflow River Taff 21 123 h 21m 5.12
Dwr Cymru Welsh Water Trenant 1 Storm Overflow River Cynon 52 120 h 41m 5
Dwr Cymru Welsh Water Tram Road Side Storm Overflow River Taff 19 118 h 9m 4.92
Dwr Cymru Welsh Water Tai Mawr Way Storm Overflow River Taff 34 97 h 5m 4.04
Dwr Cymru Welsh Water Rocky Road 1 Storm Overflow Nant Morlais 49 94 h 4m 3.92
Dwr Cymru Welsh Water Heol Pendarren Storm Overflow Ditch to Nant Gwrangon 36 90 h 18m 3.75
Dwr Cymru Welsh Water Bute Place Hirwaun Storm Overflow River Cynon 24 87 h 57m 3.62
Dwr Cymru Welsh Water Pen-Y-Darren Rd jct with Gwalia Place Storm Overflow Morlais Brook 51 87 h 27m 3.62
Dwr Cymru Welsh Water Bro Deg 1 Storm Overflow River Cynon 38 84 h 40m 3.5
Dwr Cymru Welsh Water Dean Street Aberdare Storm Overflow River Cynon 39 60 h 45m 2.5
Dwr Cymru Welsh Water Aberaman Curre Street Storm Overflow Unnamed Stream 21 49 h 34m 2.04
Dwr Cymru Welsh Water Llwydcoed Road New Scales Houses Storm Overflow Unnamed Tribuatary of Afon Cynon 15 46 h 27m 1.92
Dwr Cymru Welsh Water Glan Road Storm Overflow River Dare 18 45 h 49m 1.88
Dwr Cymru Welsh Water Wind Street Storm Overflow River Amman 32 44 h 9m 1.83
Dwr Cymru Welsh Water Cyfarthfa Road Storm Overflow River Taff 27 42 h 12m 1.75
Dwr Cymru Welsh Water Elizabeth Street Storm Overflow Tributary of River Cynon 13 40 h 32m 1.67
Dwr Cymru Welsh Water Sion Terrace Storm Overflow River Cynon 18 37 h 57m 1.54
Dwr Cymru Welsh Water Commercial Street Aberdare Overflow River Cynon 39 31 h 24m 1.29
Dwr Cymru Welsh Water Merthyr Vale Trunk Sewer Storm Overflow River Taff 4 30 h 31m 1.25
Dwr Cymru Welsh Water Swan Street Merthyr Tydfil Storm Overflow River Taff 17 26 h 17m 1.08
Dwr Cymru Welsh Water David Street Aberaman Storm Overflow River Cynon 2 24 h 59m 1
Dwr Cymru Welsh Water Pont-y-Cefn Storm Overflow Taf Fechan 15 23 h 10m 0.96
Dwr Cymru Welsh Water Yew Street Storm Overflow River Taff 10 21 h 26m 0.88
Dwr Cymru Welsh Water Cardiff Road Aberaman Storm Overflow River Cynon 12 18 h 24m 0.75
Dwr Cymru Welsh Water Canal Road Cwmbach Storm Overflow River Cynon 8 18 h 1m 0.75
Dwr Cymru Welsh Water Goitre Lane Storm Overflow Goitre Brook 13 17 h 22m 0.71
Dwr Cymru Welsh Water Nr Aberaman Park Ind. Est. Storm Overflow RiverAman 11 14 h 27m 0.58
Dwr Cymru Welsh Water Bron Haul Storm Overflow River Cynon 5 14 h 13m 0.58
Dwr Cymru Welsh Water Bro Deg Canal Road Junction Storm Overflow River Cynon 27 12 h 48m 0.5
Dwr Cymru Welsh Water Erw Las Rear Footpath Storm Overflow River Cynon 9 12 h 8m 0.5
Dwr Cymru Welsh Water Troedyrhiw Storm Overflow River Taff 2 10 h 29m 0.42
Dwr Cymru Welsh Water Foundry View Aberaman No 2 Storm Overflow River Amman 9 10 h 17m 0.42
Dwr Cymru Welsh Water Cwmbach Storm Overflow River Cynon 2 9 h 0.38
Dwr Cymru Welsh Water Pit Place Cwmbach Overflow River Cynon 7 8 h 57m 0.33
Dwr Cymru Welsh Water Abernant Road Aberdare Storm Overflow Nant Wenallt 16 6 h 53m 0.25
Dwr Cymru Welsh Water Phyllis Street Storm Overflow River Taff 10 6 h 26m 0.25
Dwr Cymru Welsh Water Glancynon Terrace Storm Overflow Nant Gwawr 13 6 h 14m 0.25
Dwr Cymru Welsh Water Hirwaun Mangoed Storm Overflow River Cynon 4 3 h 43m 0.12
Dwr Cymru Welsh Water Tudor Terrace Rear Storm Overflow Gadlys Feeder 4 3 h 26m 0.12
Dwr Cymru Welsh Water Park View Terrace Storm Overflow River Cynon 5 3 h 23m 0.12
Dwr Cymru Welsh Water Fforchaman Road Cwmaman River Amman 1 2 h 45m 0.08
Dwr Cymru Welsh Water Wellington St No1 Storm overflow River Cynon 3 1 h 14m 0.04
Dwr Cymru Welsh Water Bryngolwg Storm Overflow River Cynon 1 0 h 59m 0
Dwr Cymru Welsh Water Rocky Road 2 Storm Overflow Morlais Brook 1 0 h 16m 0
Dwr Cymru Welsh Water Foundry View Aberaman No 1 Overflow River Amman 1 0 h 15m 0
Dwr Cymru Welsh Water Market Street Dowlais Storm Overflow Unnamed Tributary Leading to Nant Morlais 1 0 h 15m 0
Dwr Cymru Welsh Water Cwmbach Maeshyfryd Stoem Overflow River Cynon 1 0 h 15m 0
Dwr Cymru Welsh Water Cynon Street Storm Overflow Unnamed Tributary to Afon Amman 1 0 h 14m 0
Dwr Cymru Welsh Water Hirwaun Tramway Storm Overflow Unnamed Stream 0 0 h 0
Dwr Cymru Welsh Water Muriel Terrace Merthyr Tydfil Overflow River Taff 0 0 h 0
Dwr Cymru Welsh Water Rodericks Terrace Storm Overflow River Taff 0 0 h 0
Dwr Cymru Welsh Water Aberfan Trunk Sewer Storm Overflow River Taff 0 0 h 0
Dwr Cymru Welsh Water Trecynon Harriet Street Storm Overflow Nant-Y-Derlwyn 0 0 h 0
Dwr Cymru Welsh Water Wyndham Crescent Aberaman Storm Overflow River Cynon 0 0 h 0
Dwr Cymru Welsh Water Balaclava Road 2 Storm Overflow Morlais Brook 0 0 h 0

Data Sources & Accuracy

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.

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© Openstreetmap contributors, Contains OS data © Crown copyright and database right 2021-2025,
Contains Water UK National Storm Overflow Hub Data CC-BY-SA 4.0 and analysis © 2025 Top-Of-The-Poops

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