Top of the Poops | Constituency Sewage Map | Merthyr Tydfil and Aberdare

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Live data for Merthyr Tydfil and Aberdare in 2026

So far this year (as of 18 May 2026, 12:00) there has been 8,587 hours of sewage overflows, from 79 CSO Combined Sewage Overflow - a device that, when operating, pours combined rainwater & sewage into a waterway s

Totals for Merthyr Tydfil and Aberdare in 2025

68 Sites polluted by Dwr Cymru Welsh Water

3,143 sewage dumps

17,554 hours duration

That's 2.03 years. On average 8.6 times a day

Change Over Time

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Constituencies near Merthyr Tydfil and Aberdare

Waterways in Merthyr Tydfil and Aberdare

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Pollution Summary 2025

Here are all the reported sewage overflow totals for Merthyr Tydfil and Aberdare in 2025. Sometimes sewage can be being dumped for months at a time.

Reporting refers to how much of the time the monitoring was active. In this constituency 4 of the total 76 CSO Combined Sewage Overflow - a device that, when operating, pours combined rainwater & sewage into a waterway locations had reporting enabled for less than half the year. Of these 4 had zero reporting.

Company	Waterway	Site	Sewage Dumps	Duration (Hours)	Reporting %
Dwr Cymru Welsh Water	River Camnant	Hirwaun Wastewater Treatment Works	170	3,660	99.8
Dwr Cymru Welsh Water	River Cynon	MIKES FIELD CSO ABERAMAN	121	1,591	99.9
Dwr Cymru Welsh Water	Taff Fechan	PONTSTICILL WWTW	90	1,411	99.8
Dwr Cymru Welsh Water	River Cynon	CSO ABERAMAN IND EST ABERAMAN	112	1,282	99.9
Dwr Cymru Welsh Water	Morlais Brook	A CSO AT WATERLOO HOUSE MERTHYR	114	656	97
Dwr Cymru Welsh Water	Taff	CSO PONT RHUN MERTHYR TYDFIL	96	628	99.9
Dwr Cymru Welsh Water	River Cynon	Penderyn CSO - Tank In Field Raked Scre	86	573	99
Dwr Cymru Welsh Water	River Cynon	CSO Opposite Arthurs Place Trecynon	96	554	99.8
Dwr Cymru Welsh Water	Taff Bargoed	CSO at Bedlinog- Bowling Green	74	537	99.1
Dwr Cymru Welsh Water	River Dare	A CSO AT FIELD ADJACENT TO DAVID ST	98	525	98.5
Dwr Cymru Welsh Water	River Cynon	CSO at West Bank Of River South Of A455 Br	88	449	99.9
Dwr Cymru Welsh Water	River Cynon	CSO At Bottom Monk Street	93	444	99.8
Dwr Cymru Welsh Water	Nant-Y-Derlwyn	ABERDARE FORECOURT CSO LLWYDCOED	77	426	99.9
Dwr Cymru Welsh Water	Aberdare Canal	Pant-Y-Cerdin CSO, Aberdare	100	424	97.3
Dwr Cymru Welsh Water	Morlais Brook	CSO at The Bont, Merthyr Tydfil	89	394	96.3
Dwr Cymru Welsh Water	Pentrebach Brook	Dixs Field CSO, Pentrebach, Merthyr	81	334	94.6
Dwr Cymru Welsh Water	River Cynon	CSO AT BOTTOM MONK STREET (Station St Aberdare)	84	307	98.7
Dwr Cymru Welsh Water	River Aman	PLEASANT VIEW CSO	90	273	92.5
Dwr Cymru Welsh Water	River Taff	A CSO AT JACKSONS BRIDGE	79	253	99.9
Dwr Cymru Welsh Water	River Taff	CSO COLLEGE CAR PK MERTHYR TYDFIL	56	251	94.1
Dwr Cymru Welsh Water	Pandy Brook	TRELEWIS CSO - REAR OF GLYNBARGOED	99	240	97.1
Dwr Cymru Welsh Water	River Cynon	Cwmbach CSO - Outside Bro Deg	70	214	98.4
Dwr Cymru Welsh Water	River Cynon	Penywaun - Rear Of 37/39 Erw L	52	176	98.8
Dwr Cymru Welsh Water	River Taff	Quakers Yard CSO, Greenfield Victoria Bridge	32	160	86.5
Dwr Cymru Welsh Water	River Taff	Quakers Yard CSO, Fiddlers Elbow St, Cynon	32	157	99.5
Dwr Cymru Welsh Water	River Cynon	CSO at Hirwaun Trenant No 66 Rear of Garden	66	152	91
Dwr Cymru Welsh Water	River Cynon	Cwmbach Bro Deg Near No44	52	150	99.1
Dwr Cymru Welsh Water	River Taff	Gellideg Tai Mawr Rd CSO, Merthyr Tydfil	47	140	99.4
Dwr Cymru Welsh Water	Morlais Brook	CSO TREVITHICK MONUMENT MERTHYR	69	127	98.7
Dwr Cymru Welsh Water	River Dare	CSO Off Glan Road (St John the Baptist Church)	42	117	99.6
Dwr Cymru Welsh Water	River Cynon	HIRWAUN - REAR OF BUTE TERRACE	40	88	97
Dwr Cymru Welsh Water	To Nant Gwrangon	CSO at Rhigos- Heol Pendarren	48	88	99.3
Dwr Cymru Welsh Water	Nant Morlais	Rocky Rd CSO Merthyr Tydfil	61	88	91.5
Dwr Cymru Welsh Water	River Cynon	ABERNANT RUGBY CLUB CSO	50	85	99.8
Dwr Cymru Welsh Water	Aman R - Source To Conf River Cynon	Aberaman Park Industrial Estate CSO, Aberdare	29	61	99.7
Dwr Cymru Welsh Water	River Cynon	Cwmbach Sion Terrace No 11 CSO	19	51	99.2
Dwr Cymru Welsh Water	River Taff	CSO Avenue De Clichy, Merthyr	31	50	99.9
Dwr Cymru Welsh Water	River Taff	Merthyr Tydfil Georgetown Lines Bridge CSO	37	45	92.8
Dwr Cymru Welsh Water	River Cynon River	Aberaman Wind St CSO Nr Mardy lodge	48	44	99.8
Dwr Cymru Welsh Water	River Cynon	CSO at Cwmbach Side of Police House	24	42	99.5
Dwr Cymru Welsh Water	River Cynon	Aberaman Curre St CSO	32	38	99.8
Dwr Cymru Welsh Water	Goitre Brook	Goitre Lane CSO	25	34	99
Dwr Cymru Welsh Water	River Cynon	Elizabeth St CSO	27	33	99.3
Dwr Cymru Welsh Water	River Aman	CSO at Aberaman Cardiff Road No 104	23	25	99.6
Dwr Cymru Welsh Water	River Cynon	Canal Rd CSO, Cwmbach	16	23	98.6
Dwr Cymru Welsh Water	River Cynon	CSO at Rear of No12 Bonhaul, Cwmbach	12	22	99.2
Dwr Cymru Welsh Water	Nant Wenallt And Then To River Cynon	Forge Tip CSO Aberdare	27	21	99.6
Dwr Cymru Welsh Water	Taf Fechan	High St CSO, Cefn Coed	28	20	99
Dwr Cymru Welsh Water	River Taff	Troedyrhiw, Yew Street CSO	16	17	81.6
Dwr Cymru Welsh Water	Nant Gwawr	CSO at No20 Glancynon Terrace, Aberaman	25	10	88.5
Dwr Cymru Welsh Water	River Cynon	Cwmbach SPS	3	10	99.9
Dwr Cymru Welsh Water	River Aman	Incline Row CSO, Aberaman	6	5	99.7
Dwr Cymru Welsh Water	River Taff	TROEDYRHIW PS	3	4	99.8
Dwr Cymru Welsh Water	River Aman	CSO at Junction of David St & Pant Rd, Aberaman	2	4	88
Dwr Cymru Welsh Water	River Cynon	Abercwmboi Parkview Capcoch Infant School CSO	7	3	100
Dwr Cymru Welsh Water	River Taff	3rd Trunk CSO South of Glan Yr Afon	8	3	97.9
Dwr Cymru Welsh Water	Gadlys Feeder	GLADLYS TUDOR TERRACE CSO	6	3	91.1
Dwr Cymru Welsh Water	Morlais Brook	Brewers Arms CSO, Balaclava Rd, Dowlais	9	2	92.5
Dwr Cymru Welsh Water	River Cynon	No 1 Wellington St CSO, Robertstown	7	2	100
Dwr Cymru Welsh Water	River Cynon	CSO at Aberaman	3	1	99.3
Dwr Cymru Welsh Water	Morlais Brook	CSO AT DOWLAIS BALACLAVA ROAD	4	1	100
Dwr Cymru Welsh Water	Aman R - Source To Conf River Cynon	Fforchaman Street CSO	2	1	99.9
Dwr Cymru Welsh Water	River Cynon	CSO at Cwmbach Bryngolwg No 45	2	0	99.9
Dwr Cymru Welsh Water	Unnamed Leading To Aman River	Aberaman Cynon St rear of	2	0	99.8
Dwr Cymru Welsh Water	Un Leading To Nant Morlais	Dowlais Market St & High St Junction	2	0	97.1
Dwr Cymru Welsh Water	River Cynon	No. 29 Maeshyfryd CSO, Cwmbach	2	0	100
Dwr Cymru Welsh Water	Morlais Brook	Balaclava Rd CSO, Dowlais	1	0	100
Dwr Cymru Welsh Water	Unnamed Stream And Thence To River Cynon	CSO at HIRWAUN - ON TRAMWAY	1	0	95.4
Dwr Cymru Welsh Water	River Taff	CSO WILLOW GAS WORKS MERTHYR TYDFIL	0	0	98.8
Dwr Cymru Welsh Water	River Cynon	CSO at Hirwaun Trenant No70 Rear of Garden	0	0	0
Dwr Cymru Welsh Water	Bargoed Taf	CSO at QUAKERS YARD - NEAR PUBLIC HOU	0	0	100
Dwr Cymru Welsh Water	River Cynon	CSO at Rear Of St Winifreds Church Hirwa	0	0	0
Dwr Cymru Welsh Water	Unnamed Leading To River Cynon	Llwydcoed CSO Side of Llwydcoed Motors	0	0	0
Dwr Cymru Welsh Water	River Taff	Phyllis Street CSO, Troedyrhiw	0	0	0
Dwr Cymru Welsh Water	River Taff	TRUNK CSO 2A OFF ABERFAN ROAD	0	0	100
Dwr Cymru Welsh Water	Nant-Y-Derlwyn	Trecynon, Harriet St CSO	0	0	99.9

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.

Analysing sewage pollution by the Water Industry

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