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Gwynedd Maldwyn

Polluted by sewage 12,099 times in 2025 lasting 103,501 hours - That's 11.98 years!

Monitoring fell below 50% in some locations so could be more

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Contains OS Data © Crown copyright & database right 2021-2024
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Totals for Gwynedd Maldwyn in 2025

211 Sites polluted by Dwr Cymru Welsh Water
12,099 sewage dumps
103,501 hours duration
That's 11.98 years. On average 33.1 times a day

Change Over Time

Senedd Constituencies near Gwynedd Maldwyn

Westminster Constituencies within Gwynedd Maldwyn

To see live data by overflow, go to the Westminster Constituency, then 'live data'

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Sewage pollution map of Gwynedd Maldwyn: 103,501 hours in 2025
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Pollution Summary 2025

Here are all the reported sewage overflow totals for Gwynedd Maldwyn 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 1 of the total 230 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.

Company Waterway Site Sewage Dumps Duration (Hours) Reporting %
Dwr Cymru Welsh Water Nant Brisgyll LLANFFESTINIOG STW 419 4,104 99.9
Dwr Cymru Welsh Water Erch ABERERCH WWTW 152 2,998 99.9
Dwr Cymru Welsh Water Erch FOURCROSSES Wastewater Treatment Works 238 2,713 99.9
Dwr Cymru Welsh Water River Glaslyn BEDDGELERT WASTE WATER TREATMENT 193 2,697 99.9
Dwr Cymru Welsh Water River Twymyn Commins Coch Pumping Station CSO 120 2,675 99.9
Dwr Cymru Welsh Water Wen CHWILOG STW 142 2,317 99.9
Dwr Cymru Welsh Water River Goedol BLAENAU FFESTINIOG WWTW 139 2,290 99
Dwr Cymru Welsh Water Rhyd Hir LLITHFAEN STW 115 2,219 99.6
Dwr Cymru Welsh Water River Cadnant BETHEL SEWAGE TRANSFER PS 129 1,968 99.6
Dwr Cymru Welsh Water Mawddach Estuary FAIRBOURNE WWTW 97 1,926 100
Dwr Cymru Welsh Water River Iaen LLANBRYNMAIR STW LLANBRYNMAIR 95 1,855 94.4
Dwr Cymru Welsh Water River Rhythallt LLANRUG WWTW FINAL 115 1,855 97.9
Dwr Cymru Welsh Water Dwyfawr LLANYSTUMDWY A WWTW 124 1,852 99.8
Dwr Cymru Welsh Water Tremadog Bay CRICCIETH STW FINAL 124 1,829 99.8
Dwr Cymru Welsh Water Mawddach Llanelltyd PS CSO 99 1,818 99.5
Dwr Cymru Welsh Water Caernarfon Bay NEFYN PUMPING STATION 131 1,816 99.9
Dwr Cymru Welsh Water River Cedron PENTREFELIN STW 104 1,634 99.9
Dwr Cymru Welsh Water Tyddin Drain To Coastal Waters TREFOR CAERNARFON 125 1,620 99.5
Dwr Cymru Welsh Water River Llyfni Nantlle PS 102 1,553 99.9
Dwr Cymru Welsh Water River Llyfni LLANLLYFNI CAERNARFON STW 113 1,504 99.8
Dwr Cymru Welsh Water Wye River LLANGURIG STW 75 1,476 99.9
Dwr Cymru Welsh Water Dwyfawr GARNDOLBENMAEN STW 98 1,393 99.9
Dwr Cymru Welsh Water River Seiont Pont Rhythallt Pumping Station 140 1,380 99.9
Dwr Cymru Welsh Water River Gwyrfai WAUNFAWR STW (FINAL EFFLUENT) 92 1,292 99.9
Dwr Cymru Welsh Water River Seiont CAERNARFON STW 90 1,251 99.8
Dwr Cymru Welsh Water Mawddach DOLGELLAU STW 77 1,232 99.9
Dwr Cymru Welsh Water River Seiont PENISARWAUN WWTW FE 161 1,199 99.9
Dwr Cymru Welsh Water River Seiont LLANBERIS WwTW 137 1,196 99.8
Dwr Cymru Welsh Water River Mawddach Penmaenpool PS 111 1,190 98.8
Dwr Cymru Welsh Water Of River Rhyd Hir EFAILNEWYDD STW 281 1,144 92.8
Dwr Cymru Welsh Water River Dyfi ABERDYFI WHARF PS SEAVIEW TERRACE 59 1,092 99.9
Dwr Cymru Welsh Water River Geirch NEFYN WWTW 99 1,060 100
Dwr Cymru Welsh Water River Geirch NEFYN WWTW 104 1,018 99.9
Dwr Cymru Welsh Water Gwyrfai LLANFAGLAN WWTW FINAL EFFLUENT 91 1,002 99.9
Dwr Cymru Welsh Water Tremadog Bay HARLECH TERMINAL PS (OUTFALL A) 57 991 99.9
Dwr Cymru Welsh Water River Prysor CSO at Trawsfynydd WwTW 70 973 99.8
Dwr Cymru Welsh Water River Dwyryd Penrhyndeudraeth CSO 127 928 99.9
Dwr Cymru Welsh Water River Bowydd CWM BOWYDD SSO BLAENAU FFESTINIOG 109 916 99.9
Dwr Cymru Welsh Water Unnamed Stream HARLECH TERMINAL PS (OUTFALL B) 55 914 99.9
Dwr Cymru Welsh Water River Rhyd Hir LLANNOR STW (SETTLED STORM) 112 899 99.9
Dwr Cymru Welsh Water Of River Soch MYNYTHO STW - STORM OVERFLOW 118 885 99.9
Dwr Cymru Welsh Water River Dee CORWEN WWTW FINAL EFFLUENT 58 881 99.9
Dwr Cymru Welsh Water Estuarial Waters Of River Dwyryd MAENTWROG WWTW 68 854 99.9
Dwr Cymru Welsh Water Ardudwy Marsh Main Drain DYFFRYN ARDUDWY WWTW FINAL EFFLUENT 56 850 99.9
Dwr Cymru Welsh Water River Llyfni Talysarn No 3 - CSO 86 827 99.9
Dwr Cymru Welsh Water Dulas North LOWER CORRIS STW 72 800 81.4
Dwr Cymru Welsh Water Cwmllechen BONTDDU STW 82 789 99.9
Dwr Cymru Welsh Water River Geirch Edern SPS CSO 69 785 99.8
Dwr Cymru Welsh Water River Ceunant Sych CSO at Land Off A496 Manod Blaenau Ffesti 123 773 97.4
Dwr Cymru Welsh Water River Dwyfawr LLANYSTUMDWY PUMPING STATION 64 728 99.7
Dwr Cymru Welsh Water Cardigan Bay BARMOUTH WWTW LONG SEA OUTFALL 173 707 99.8
Dwr Cymru Welsh Water River Dee BALA WWTW 92 693 99.8
Dwr Cymru Welsh Water Unknown CSO at Tai Craig-y-don Cwymyglo 41 653 97.7
Dwr Cymru Welsh Water River Eden BRONABER STW 78 636 99.7
Dwr Cymru Welsh Water River Barlwyd LAND OPP GLANLLYN NR OAKLEY SQUARE CSO 117 634 99.5
Dwr Cymru Welsh Water River Caledffrwd Llwyn Celyn CSO Deinolen 129 629 97.9
Dwr Cymru Welsh Water Tafarn Helyg GELLILYDAN STW 81 607 99.9
Dwr Cymru Welsh Water Nant Brisgyll CSO at Llan Ffestiniog Sewage Treatment Works 50 568 100
Dwr Cymru Welsh Water River Llyfni Talysarn No 4 - CSO 87 567 99.8
Dwr Cymru Welsh Water Tremadog Bay Llanbedrog SPS 36 561 99.7
Dwr Cymru Welsh Water River Prysor TRAWSFYNYDD STW 50 555 100
Dwr Cymru Welsh Water Coastal Waters FAIRBOURNE WWTW STORM TANKS 28 554 99.7
Dwr Cymru Welsh Water River Gwyrfai Bontnewydd CSO 98 515 94.7
Dwr Cymru Welsh Water Cyt Mawr Stream TALSARNAU STW 73 508 99.9
Dwr Cymru Welsh Water River Rhydhir LON COB BACH PS PWLLHELI 67 494 98.8
Dwr Cymru Welsh Water Tyddyn Drain To Coastal Waters TREFOR WWTW 38 482 100
Dwr Cymru Welsh Water River Dyfrdwy The Eagles CSO, Llanwchllyn 60 479 98.9
Dwr Cymru Welsh Water Llyfni PONTLLYFNI PS 44 465 99.9
Dwr Cymru Welsh Water Garsiwn Ditch MACHYNLLETH STW CSO 65 460 98.7
Dwr Cymru Welsh Water River Goedol CSO at Land Off Pencefn Road Tanygrisiau 80 446 98.9
Dwr Cymru Welsh Water River Glaslyn CSO at Porthmadog Borth-Y-Gest SPS 135 446 99.8
Dwr Cymru Welsh Water River Glaslyn CSO at Beddgelert East Bank Afon Glaslyn 59 438 97.5
Dwr Cymru Welsh Water River Carrog CSO at Caernarfon Hen Gastell No5 80 437 99.1
Dwr Cymru Welsh Water Coastal Waters Of Cardigan Bay TYWYN STW MORFA GWYLLT TYWYN 83 432 99.8
Dwr Cymru Welsh Water Dyfi MACHYNLLETH STW 55 410 98.6
Dwr Cymru Welsh Water Coastal Waters CRICCIETH EAST PS , , 56 399 96.4
Dwr Cymru Welsh Water Tremadog Bay CRICCIETH WEST PS , , 51 398 99
Dwr Cymru Welsh Water Dysynni Low Level Drainage Cha TYWYN STW MORFA GWYLLT TYWYN , 73 385 99.8
Dwr Cymru Welsh Water Unnamed Ditch CASTELL PUMPING STATION 39 375 99.4
Dwr Cymru Welsh Water Tremadog Bay CRICCIETH EAST PS 32 365 99.8
Dwr Cymru Welsh Water Seiont CAERNARFON PONT SEIONT PS 41 354 99.7
Dwr Cymru Welsh Water River Gwyrfai CSO at Bontnewydd Glanrafon No10 73 351 99.1
Dwr Cymru Welsh Water River Wnion Marian Mawr CSO 105 343 99.9
Dwr Cymru Welsh Water River Llyfni Llanllyfni Glan Aber CSO 130 340 99
Dwr Cymru Welsh Water Unnamed Ditch ARTHOG TERRACE SEWAGE PUMPING ST 41 334 99.9
Dwr Cymru Welsh Water River Goedol BLAENAU FFESTINIOG WWTW (Settled STORM) 22 334 100
Dwr Cymru Welsh Water Unnamed Stream Clynnog Fawr CSO at PS 68 333 99.9
Dwr Cymru Welsh Water Unnamed Stream CSO At Corwen Rear Of The Pavillion 73 329 97.9
Dwr Cymru Welsh Water River Dee CEFN MAWR WwTW 48 318 99.9
Dwr Cymru Welsh Water Tremadog Bay LLANDANWG TERMINAL PS 25 315 99.9
Dwr Cymru Welsh Water River Goch Pant CSO 73 313 99.9
Dwr Cymru Welsh Water Dyffryn Main Drain DYFFRYN ARDUDWY WWTW STORM 23 310 100
Dwr Cymru Welsh Water River Seiont CAERNARFON WWTW INLET PUMP ST 6MM 83 301 99.8
Dwr Cymru Welsh Water Cyt Bach Surface Watercourse SNOWDON STREET PS 88 300 99.9
Dwr Cymru Welsh Water River Ceidiog LLANDRILLO STW 20 299 100
Dwr Cymru Welsh Water River Blaen-Y-Cae BRYNCIR STW 59 297 99.9
Dwr Cymru Welsh Water River Caledffwrd BRYNREFAIL MAIN SPS 52 296 99.9
Dwr Cymru Welsh Water Dee CYNWYD STW FINAL EFFLUENT 83 292 99.9
Dwr Cymru Welsh Water River Llyfni Settled Storm Sewage at Llanllyfni WwTW 27 280 99.9
Dwr Cymru Welsh Water Llyn Nantlle Uchaf Nantlle No 5-CSO 68 272 98.7
Dwr Cymru Welsh Water Cegin RHIWLAS STW 99 266 99.9
Dwr Cymru Welsh Water Goch Bach CSO Near Castle Gift Shop Llanberis 50 266 99.6
Dwr Cymru Welsh Water Carrog CAERNARFON - RHOSTRYFAN CSO NO 81 262 99.9
Dwr Cymru Welsh Water Un-Named Stream Into Llifon Dorlan Goch CSO 77 260 98.8
Dwr Cymru Welsh Water River Artro LLANBEDR TERMINAL PS (STORM) 36 250 99.7
Dwr Cymru Welsh Water River Ceidiog Llandrillo STW PS CSO 64 238 99.9
Dwr Cymru Welsh Water Rhyd CAERNARFON - GLANRHYD SSO NO. 63 220 96
Dwr Cymru Welsh Water River Geirch MORFA NEFYN PUMPING STATION CSO (B) 80 207 98.7
Dwr Cymru Welsh Water Coastal Waters Llwyngwril SPS 32 202 99.9
Dwr Cymru Welsh Water River Wnion STAYLITTLE LANE CSO 51 198 99.9
Dwr Cymru Welsh Water River Aber Glesyrch Ceinws SPS 20 197 99.8
Dwr Cymru Welsh Water Gwyrfai CAERNARFON - RHOSTRYFAN CSO NO 56 197 99.5
Dwr Cymru Welsh Water Cadnant - Caernarfon SSO AT MILL LANE CAERNARFON 87 194 99.9
Dwr Cymru Welsh Water Tremadog Bay MORFA BYCHAN WWTW 58 184 99.9
Dwr Cymru Welsh Water River Dysynni Abergynolwyn STW (Settled Storm) 38 181 99.9
Dwr Cymru Welsh Water Desach ABERDESACH PS 72 171 99.9
Dwr Cymru Welsh Water Glaslyn Estuary PORTHMADOG STW STORM STORAGE PORT 56 164 99.9
Dwr Cymru Welsh Water Tref Y Nant Brook CEFN PS 46 157 99.5
Dwr Cymru Welsh Water River Llifon Caernarfon - Llwyn Gwalch CSO Groes 59 149 99.9
Dwr Cymru Welsh Water Menai Strait FELINHELI PS (QUAY COTTAGE) , , 23 148 99.9
Dwr Cymru Welsh Water Tremadog Bay CRICCIETH WEST PS 30 147 93.7
Dwr Cymru Welsh Water Glanyrafon Brook Rhostyllen Bersham Colliery CSO 52 145 99.5
Dwr Cymru Welsh Water River Llyfni PONTLLYFNI STW 28 142 99.9
Dwr Cymru Welsh Water River Henddol FAIRBOURNE PUMPING STATION 22 139 99.9
Dwr Cymru Welsh Water Un-Named Watercourse BRYNCOCH SEWAGE PUMPING STATION 13 131 99.9
Dwr Cymru Welsh Water River Glaslyn BORTH Y GES PS 41 125 99.7
Dwr Cymru Welsh Water River Gwyrfai Bontnewydd CSO Ysgol Gynradd Bontne 47 124 99.9
Dwr Cymru Welsh Water Ffos Ddu Marian Mawr Splitter Chamber CSO 22 111 99.8
Dwr Cymru Welsh Water River Hwch Llanberis CSO NO. 2 45 104 97.8
Dwr Cymru Welsh Water River Seiont Peblig Industrial Estate CSO 37 97 98.2
Dwr Cymru Welsh Water Menai Straits CROSSVILLE CSO 67 95 99.9
Dwr Cymru Welsh Water Nant Brisgyll CSO at Llanffestiniog STW 15 95 100
Dwr Cymru Welsh Water River Goch Afon Eitha CSO 52 88 98.9
Dwr Cymru Welsh Water Coastal Waters - River Daron ABERDARON PS 25 86 99.8
Dwr Cymru Welsh Water Groundwater Via Infiltration System WESLEYAN TERRACE SEWAGE PUMPING ST 8 86 99.9
Dwr Cymru Welsh Water Garsiwn River Dovey Machynlleth - Doll Street CSO 62 86 99
Dwr Cymru Welsh Water River Dysynni Abergynolwyn SPS 36 83 99.9
Dwr Cymru Welsh Water River Prysor Trawsfynydd Maesgwindy Est CSO 55 82 99.9
Dwr Cymru Welsh Water River Glaslyn BRITANNIA PS 10 80 99.9
Dwr Cymru Welsh Water Ditch Idris Villas Sewage Pumping Station 40 76 99.9
Dwr Cymru Welsh Water River Llan CAERNARFON - PENYGROES SSO NO. 53 75 99.9
Dwr Cymru Welsh Water River Penrhos PENRHOS CAMP STW - SCREENED ST 31 74 99.8
Dwr Cymru Welsh Water River Ceiriog DOL Y WERN - CSO 32 69 99.6
Dwr Cymru Welsh Water River Cadnant BETHEL CSO BETHEL NEAR CAERNARFON 31 67 99.2
Dwr Cymru Welsh Water River Eitha Penycae SPS 17 66 99.9
Dwr Cymru Welsh Water River Rhyd Hir Estuary Y MAES CSO 32 61 99.8
Dwr Cymru Welsh Water Tref Y Nant Brook Cefn Monsanto CSO 28 58 99.5
Dwr Cymru Welsh Water Black Spool Johnstown Combined Sewerage System CSO 32 55 99.9
Dwr Cymru Welsh Water Stream Leading To Cyt Stre TREMADOG SSO 16 54 99.9
Dwr Cymru Welsh Water River Goch Bersham Colliery CSO 36 53 99.9
Dwr Cymru Welsh Water River Bradley CHIRK PS (SCREENED STROM) 24 52 99.8
Dwr Cymru Welsh Water Eitha Ruabon PS 20 51 99.9
Dwr Cymru Welsh Water Cadnant BETHEL SSO NO. 3 15 51 99.9
Dwr Cymru Welsh Water Unnamed Watercourse Fford Offa CSO 31 48 99.2
Dwr Cymru Welsh Water River Dyfi MACHYNLLETH WWTW (STORM OUTFALL) 9 47 99.3
Dwr Cymru Welsh Water Llyn Padarn LLANBERIS PS , , 15 47 98.9
Dwr Cymru Welsh Water River Dee Chirk O/S 24 Offa St CSO 14 45 99.6
Dwr Cymru Welsh Water River Wen AFONWEN WASTEWATER TREATMENT WORKS 10 40 99.9
Dwr Cymru Welsh Water Unnamed Ditch GLASFRYN TERRACE STW ARTHOG 5 36 99.9
Dwr Cymru Welsh Water Unnamed Watercourse CAERNARFON MARGARET STREET SSO 57 36 98.7
Dwr Cymru Welsh Water Artro LLANBEDR WWTW 12 35 99.8
Dwr Cymru Welsh Water River Ceiriog Glynceiriog Y Gammer - CSO 45 33 98.7
Dwr Cymru Welsh Water Cardigan Bay BARMOUTH WWTW OUTFALL TO MLWS 23 32 99.9
Dwr Cymru Welsh Water Dwyryd PENRHYNDEUDRAETH OUTFALL-SCREE 5 30 99.8
Dwr Cymru Welsh Water River Seiont Caernarfon WWTW Inlet Pump ST 6mm SPS 18 28 99.8
Dwr Cymru Welsh Water Un-Named Stream PORTHMADOG - LOMBARD STREET SS 52 20 99.9
Dwr Cymru Welsh Water Eitha Ruabon Paddock Row CSO 7 20 96.9
Dwr Cymru Welsh Water Glanyrafon Brook CSO at COLLIERY ROAD RHOSTYLLEN 19 19 99.7
Dwr Cymru Welsh Water Unnamed Stream FRIOG SEWAGE PUMPING STATION 9 18 99.9
Dwr Cymru Welsh Water Black Brook Aberderfyn CSO, Rhosllanerchrugog 13 18 84.4
Dwr Cymru Welsh Water Unnamed Stream Trefor CSO 17 17 41.7
Dwr Cymru Welsh Water River Y Llan LLANFACHRETH WWTW 26 16 95.4
Dwr Cymru Welsh Water River Dee Rhosymedre Park Rd CSO 11 16 99.2
Dwr Cymru Welsh Water River Daron ABERDARON WASTEWATER TREATMENT WKS 15 15 99.4
Dwr Cymru Welsh Water River Laen CSO at Llanbrynmair STW Llanbrynmair 3 14 100
Dwr Cymru Welsh Water Tremadog Bay CSO at Llandanwg SPS 2 14 99.8
Dwr Cymru Welsh Water River Prysor CSO at Trawsfynydd Near Bron Gwyndy 23 14 97.5
Dwr Cymru Welsh Water Cadnant MIN-Y-NANT CSO 27 14 99.7
Dwr Cymru Welsh Water River Dee Newbridge SPS 7 14 99.7
Dwr Cymru Welsh Water Barlwyd BLAENAU FFESTINIOG NO2 12 13 98.6
Dwr Cymru Welsh Water Unnamed Stream HARLECH OUTSIDE LAUNDRY 17 12 99.9
Dwr Cymru Welsh Water Un-Named Watercourse LLANERCH CSO 25 9 99.6
Dwr Cymru Welsh Water Tremadog Bay MORFA BYCHAN WWTW 2 9 100
Dwr Cymru Welsh Water Angell Aberangell No1 PS 1 8 97.4
Dwr Cymru Welsh Water Garsiwn Ditch Heol Penrallt CSO 14 8 99.9
Dwr Cymru Welsh Water River Dee Corwen Corner Station Yard CSO 4 7 99.6
Dwr Cymru Welsh Water Un-Named Watercourse Machynlleth - Popular Road CSO 21 7 91.1
Dwr Cymru Welsh Water Tremadog Bay CSO ON SEWER (CRICCIETH BEACH) 6 7 99.9
Dwr Cymru Welsh Water Unnamed Stream CSO Rear Of Prysor Filling Station Traw 17 7 99.9
Dwr Cymru Welsh Water River Penrhos CSO at Penrhos WwTW 6 7 100
Dwr Cymru Welsh Water River Mawddach Llanelltyd CSO 13 7 97.3
Dwr Cymru Welsh Water Mawddach Estuary BARMOUTH HARBOUR PUMPING STATION 16 7 99.9
Dwr Cymru Welsh Water River Soch Estuary ABERSOCH HARBOUR PUMPING STATION 4 6 99.9
Dwr Cymru Welsh Water Glaslyn Estuary Within Glaslyn PORTHMADOG STW STORM STORAGE PORT 7 6 99.9
Dwr Cymru Welsh Water River Caledffrwd CSO at Pen yr Olchfa Clwt Y Bont Deiniolen 4 3 98.1
Dwr Cymru Welsh Water Esturial Waters River Erch GLAN Y DON PS PWLLHELI 6 3 99.3
Dwr Cymru Welsh Water Dulas North Minffordd St CSO, Corris 5 3 96.6
Dwr Cymru Welsh Water River Dwyryd Harlech Rum Hole CSO 12 3 99
Dwr Cymru Welsh Water Nant Y Cyt CHAPEL STREET/MADOG STREET PORTHM 9 3 99.5
Dwr Cymru Welsh Water River Dee CSO at Rear Hamden Way Plas Madoc 4 1 99.6
Dwr Cymru Welsh Water River Dwyryd MAENTWROG CSO 5 1 100
Dwr Cymru Welsh Water River Eitha Penycae West End School Field Land CSO 5 1 99.5
Dwr Cymru Welsh Water River Cyll-Y-Felin CSO at Aberdaron WwTW 2 1 99.5
Dwr Cymru Welsh Water River Ceiliog DOLYWERN STW 2 1 99.9
Dwr Cymru Welsh Water River Glaslyn AMMANDA TERRACE BORTH Y GEST PORTHM 3 0 100
Dwr Cymru Welsh Water Cadnant BETHEL SSO NO. 2 3 0 99.9
Dwr Cymru Welsh Water River Fathew BRYNCRUG PS 2 0 99.6
Dwr Cymru Welsh Water River Bowydd Blaenau Ffestiniog CSO No 3 2 0 99.9
Dwr Cymru Welsh Water Mawddach MAWDDACH CRESCENT PUMPING STATION 2 0 99.8
Dwr Cymru Welsh Water Menai Straits BALACLAVA ROAD SEWAGE PUMPING ST 1 0 99.8
Dwr Cymru Welsh Water Unnamed Flowing To Bradley Brook Chirk Chapel Lane CSO 1 0 96.3
Dwr Cymru Welsh Water River Siont ANGLESEY ARMS PUMPING STATION 0 0 100
Dwr Cymru Welsh Water Nant Y Cyt BAKERS LANE/CHANDLERS PLACE PORTH 0 0 99.7
Dwr Cymru Welsh Water River Erch BRIDGE GARAGE PWLLHELI 0 0 99.6
Dwr Cymru Welsh Water River Bowydd Blaenau Ffestiniog WWTW Settled Storm (B) 0 0 100
Dwr Cymru Welsh Water Menai Straits CAERNARFON BANK QUAY PS 0 0 99.9
Dwr Cymru Welsh Water Dee Via Surface Water Sewer And Culvert Corwen Clawdd Poncen PS 0 0 99.9
Dwr Cymru Welsh Water River Mawddach Dolgellau Main PS 0 0 99.9
Dwr Cymru Welsh Water Menai Strait FELINHELI PS (ADJ TO QUAY TOILETS) 0 0 99.9
Dwr Cymru Welsh Water Menai Strait FELINHELI PS (OPP SEA CADET CORPS) 0 0 99.9
Dwr Cymru Welsh Water Esturial Waters Of River Erch GIMBLET ROCK TIDAL TANK CSO 0 0 99.9
Dwr Cymru Welsh Water Unnamed Culvert To River Artro Llanbedr CSO 0 0 100
Dwr Cymru Welsh Water Un-Named Stream MORFA BYCHAN WWTW 0 0 100
Dwr Cymru Welsh Water Esturial Waters Of River Erch MORFA GARREG PS PWLLHELI 0 0 99.9
Dwr Cymru Welsh Water Groundwater Via Infiltration System ST MARY'S SEWAGE PUMPING STATION 0 0 99.1
Dwr Cymru Welsh Water Menai Strait WATERLOO PORT SEWAGE PUMPING ST 0 0 99.2
Dwr Cymru Welsh Water River Bradley CHIRK PS (SCREENED STORM) 0 0 99.8
Dwr Cymru Welsh Water River Goch CSO at Ruabon Combined Sewerage System 0 0 99.9
Dwr Cymru Welsh Water River Twymyn LLAN LLANBRYNMAIR PS CSO 0 0 99.9
Dwr Cymru Welsh Water Garsiwn Ditch MACHYNLLETH STW 0 0 98.7

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

Annual figures up to and including 2025 come from official water company returns. The 2026 figure is our own estimate, derived continuously from the companies' live data feeds.

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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