Top of the Poops | Constituency Sewage Map

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You're looking at the totals that we have calculated for sewage in Ynys Môn so far for 2026. It is an estimate, based on very poor quality live data from the Water Companies. The water companies report their sewage to the Environment Agency every year in April. You can see the last reported year in the other page

What's a potential overflow? If the CSO goes 'Offline' while its Overflowing, we don't know if it stopped overflowing until we get a 'Stop' event.

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Your local MP is Llinos Medi (Plaid Cymru) - Find out more about their interests, donors, and voting at They Work For You

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Company	Site Name	Receiving Waterway	Overflow Days	Total Duration (hours)	Offline/Potential Pollution
Dwr Cymru Welsh Water	Bryngwran WwTW Overflow	Crigyll	51	1,177 h 35m	-
Dwr Cymru Welsh Water	Llanfachraeth WwTW Overflow	River Alaw	55	1,168 h 49m	-
Dwr Cymru Welsh Water	Llangaffo WwTW Storm Overflow	Unnamed Stream	56	700 h 51m	-
Dwr Cymru Welsh Water	Green Terrace Llangaffo Storm Overflow	Unnamed Ditch	20	422 h 44m	-
Dwr Cymru Welsh Water	Brynsiencyn WwTW Storm Overflow	Menai Strait	43	397 h 3m	-
Dwr Cymru Welsh Water	Talwrn Llangefni Storm Overflow	Unnamed Ditch	24	390 h	-
Dwr Cymru Welsh Water	Craig Y Don Storm Overflow	Afon Goch	25	291 h 30m	-
Dwr Cymru Welsh Water	Llandegfan Menai Bridge Storm Overflow	Afon Cadnant	23	286 h 53m	-
Dwr Cymru Welsh Water	Menai Llandegfan Storm Overflow	Menai Strait	15	253 h 27m	-
Dwr Cymru Welsh Water	Llanfechell WwTW Storm Overflow	Afon Meddanen	15	240 h 59m	-
Dwr Cymru Welsh Water	Train Station Gaerwen Storm Overflow	Tributary of Afon Braint	16	180 h 15m	-
Dwr Cymru Welsh Water	Bull Bay Storm Overflow	Bull Bay	14	124 h 45m	-
Dwr Cymru Welsh Water	Hermon Malltraeth Storm Overflow	Afon Frechwen	7	112 h 45m	-
Dwr Cymru Welsh Water	Aberffraw WwTW Storm Overflow	Aberffraw Bay	9	99 h 20m	-
Dwr Cymru Welsh Water	Lon Sardis Bodffordd Storm Overflow	Cefni Reservoir Bypass Channel	19	89 h 15m	-
Dwr Cymru Welsh Water	London Road Valley Storm Overflow	Unnamed Watercourse	12	87 h 30m	-
Dwr Cymru Welsh Water	Holyhead Porth Y Felin Storm Overflow	Unnamed Ditch draining to New Harbour	9	77 h 30m	-
Dwr Cymru Welsh Water	Rhosybol Gorslwyd Storm Overflow	Unnamed Watercourse	21	76 h 30m	-
Dwr Cymru Welsh Water	Star Gaerwen Storm Overflow	Afon Braint	9	68 h 30m	-
Dwr Cymru Welsh Water	Copperfield Close Four Mile Bridge Storm Overflow	Holy Island Straits South	6	65 h 15m	-
Dwr Cymru Welsh Water	Llanfair Pwllgwyngyll WwTW Storm Overflow	Menai Strait	19	65 h 15m	-
Dwr Cymru Welsh Water	Llanfaelog Storm Overflow	Llyn Maelog	6	54 h 28m	-
Dwr Cymru Welsh Water	Pont Y Crug Llanddaniel Storm Overflow	Afon Braint	9	37 h 41m	-
Dwr Cymru Welsh Water	Gorad Beach Road Storm Overflow	Estuarial Waters of Afon Alaw	5	33 h 58m	-
Dwr Cymru Welsh Water	Gorsllwyd Llanddona Storm Overflow	Afon Cadnant	6	30 h 49m	-
Dwr Cymru Welsh Water	Newborough WwTW Storm Overflow	Afon Braint	9	24 h 38m	-
Dwr Cymru Welsh Water	Benllech WwTW Storm Overflow	Coastal Waters - Benllech	8	20 h	-
Dwr Cymru Welsh Water	Menai Bridge Faelog Causeway 1 Overflow	Menai Strait	7	16 h	-
Dwr Cymru Welsh Water	Menai Ville Storm Overflow	Menai Strait	7	16 h	-
Dwr Cymru Welsh Water	Afon Goch Lon Parys Amlwch Storm Overflow	Afon Goch	3	13 h 15m	-
Dwr Cymru Welsh Water	Holyhead Turkey Shore Storm Overflow	Old Harbour Holyhead	7	12 h 30m	-
Dwr Cymru Welsh Water	Lon Sardis Storm Overflow	River Cefni	9	10 h 6m	-
Dwr Cymru Welsh Water	Llangoed Lleiniog Overflow	Menai Strait	4	9 h 42m	-
Dwr Cymru Welsh Water	Beaumaris & Llanfaes WwTW Storm Overflow	Menai Strait	3	9 h	-
Dwr Cymru Welsh Water	London Road Valley no.2 Storm Overflow	Unname Watercourse	6	8 h 45m	-
Dwr Cymru Welsh Water	Holyhead Bae Trearthur No1 Storm Overflow	Estuarial Waters of the Inland Sea	5	6 h 45m	-
Dwr Cymru Welsh Water	Menai Bridge Suspension Storm Overflow	Menai Strait	4	5 h 30m	-
Dwr Cymru Welsh Water	Menai Suspension Bridge No 3 Overflow	Menai Strait	4	5 h 30m	-
Dwr Cymru Welsh Water	Rhosneigr Overflow	Irish Sea	1	5 h 15m	-
Dwr Cymru Welsh Water	Prince of Wales Road Storm Overflow	New Harbour, Holyhead	6	5 h	-
Dwr Cymru Welsh Water	Waterside Holyhead Storm Overflow	New Harbour, Holyhead	3	4 h 45m	-
Dwr Cymru Welsh Water	Ffordd Y Traeth Cemaes Bay Storm Overflow	Cemaes Bay	1	3 h 45m	-
Dwr Cymru Welsh Water	Moelfre Car Park Storm Overflow	Coastal Waters of the Irish Sea	1	2 h 45m	-
Dwr Cymru Welsh Water	Fryars Bay Llanfaes Overflow	Menai Strait	1	2 h 30m	-
Dwr Cymru Welsh Water	Rhosneigr Storm Overflow	Coastal Waters - Irish Sea	1	1 h 45m	-
Dwr Cymru Welsh Water	Holyhead WwTW Overflow	Unnamed Watercourse	1	1 h 30m	-
Dwr Cymru Welsh Water	Fford Cae Sel Storm Overflow	Drainage Ditch	2	1 h 14m	-
Dwr Cymru Welsh Water	Pont y Brenin Overflow	Afon y Brenin	2	1 h 14m	-
Dwr Cymru Welsh Water	Gwalchmai WwTW Storm Overflow	Nant Cwyrtai	2	1 h 3m	-
Dwr Cymru Welsh Water	Malltraeth WwTW Inlet Storm Overflow	Cefni Estuary	1	1 h 2m	-
Dwr Cymru Welsh Water	Llandegfan Rhianfa Overflow	Menai Strait	2	0 h 59m	-
Dwr Cymru Welsh Water	Glyn Garth Overflow	Menai Strait	1	0 h 33m	-
Dwr Cymru Welsh Water	Cycle Way Llangefni Storm Overflow	Afon Cefni	2	0 h 27m	-
Dwr Cymru Welsh Water	Holyhead Morawelon Storm Overflow	Outer Harbour, Holyhead	7	0 h 22m	-
Dwr Cymru Welsh Water	Beaumaris West End Overflow	Menai Strait	1	0 h 15m	-
Dwr Cymru Welsh Water	Lon Fain Dwyran Storm Overflow	River Braint	1	0 h 15m	-
Dwr Cymru Welsh Water	Gaerwen WwTW Storm Overflow	Afon Cefni	0	0 h	-
Dwr Cymru Welsh Water	Gorwelion Road Newlands Beach Storm Overflow	Estuary Afon Alaw	0	0 h	-
Dwr Cymru Welsh Water	Llanfaes Overflow	Unnamed Watercourse	0	0 h	-
Dwr Cymru Welsh Water	Unknown	Unknown	0	0 h	-
Dwr Cymru Welsh Water	Beaumaris Green Storm Overflow	Menai Strait	0	0 h	-
Dwr Cymru Welsh Water	Llangefni WwTW Storm Overflow	Afon Cefni	0	0 h	-
Dwr Cymru Welsh Water	Benllech Old Tidal Tanks Storm Overflow	Coastal Waters - Benllech	0	0 h	-
Dwr Cymru Welsh Water	Beaumaris Green Overflow	Estuarial Waters	0	0 h	-
Dwr Cymru Welsh Water	Menai Bridge Porth Wrach No 2 Overflow	Menai Strait	0	0 h	-
Dwr Cymru Welsh Water	Aberffraw Storm Overflow	River Ffraw	0	0 h	-
Dwr Cymru Welsh Water	High Street Malltraeth Storm Overflow	Afon Cefni	0	0 h	-
Dwr Cymru Welsh Water	Bae Trearthur Lon Isallt Storm Overflow	Adjacent Ditch	0	0 h	-
Dwr Cymru Welsh Water	Malltraeth Overflow	Afon Cefni	0	0 h	-
Dwr Cymru Welsh Water	Penrhos Beach Holyhead Storm Overflow	Beddmanarch Bay	0	0 h	-
Dwr Cymru Welsh Water	Unknown	Unknown	0	0 h	-
Dwr Cymru Welsh Water	Brynsciencyn Overflow	Menai Strait	0	0 h	-
Dwr Cymru Welsh Water	Pentraeth Tan Y Graig Storm Overflow	River Nodwydd	0	0 h	-
Dwr Cymru Welsh Water	Llanfair PG Anglesey No 2 Storm Overflow	Menai Strait	0	0 h	-
Dwr Cymru Welsh Water	Bodedern Main Storm Overflow	River Alaw	0	0 h	-
Dwr Cymru Welsh Water	Llansadwrn Anglesy Storm Overflow	Afon Cadnant	0	0 h	-
Dwr Cymru Welsh Water	Millbank Storm Overflow	Unnamed Watercourse	0	0 h	-
Dwr Cymru Welsh Water	Llangoed Cynlais Overflow	Coastal Waters	0	0 h	-
Dwr Cymru Welsh Water	Arosfa Road Dwyran Storm Overflow	Afon Braint	0	0 h	-
Dwr Cymru Welsh Water	Unknown	Unknown	0	0 h	-
Dwr Cymru Welsh Water	Llansadwrn Anglesey Storm Overflow	Tributary of Afon Cadnant	0	0 h	-
Dwr Cymru Welsh Water	Bae Trearthur Isallt Bach Overflow	Caernarfon Bay North	0	0 h	-
Dwr Cymru Welsh Water	Lon Gardener Valley Overflow	Unnamed Watercourse	0	0 h	-
Dwr Cymru Welsh Water	Llanerchymedd WwTW Storm Overflow	River Alaw	0	0 h	-
Dwr Cymru Welsh Water	Unknown	Unknown	0	0 h	-
Dwr Cymru Welsh Water	Holyhead Hibernia Row Storm Overflow	New Harbour, Holyhead	0	0 h	-
Dwr Cymru Welsh Water	Holyhead Bae Trearthur No2 Storm Overflow	Unnamed Watercourse	0	0 h	-
Dwr Cymru Welsh Water	Llangefni Main Storm Overflow	Afon Cefni	0	0 h	-
Dwr Cymru Welsh Water	Brynsiencyn Main Storm Overflow	Menai Strait	0	0 h	-
Dwr Cymru Welsh Water	Plas Y Ffrwd Rhosybol Storm Overflow	River Alaw	0	0 h	-
Dwr Cymru Welsh Water	Gwalchmai Isaf Storm Overflow	Unnamed Watercourse	0	0 h	-
Dwr Cymru Welsh Water	Unknown	Unknown	0	0 h	-
Dwr Cymru Welsh Water	Malltraeth WwTW Storm Overflow	Cefni Estuary	0	0 h	-
Dwr Cymru Welsh Water	Amlwch Port Storm Overflow	Coastal Waters - Amlwch Harbour	0	0 h	-
Dwr Cymru Welsh Water	Llaneilian Storm Overflow	Coastal Waters	0	0 h	-

It's a Dirty Business

Ynys Môn - Live Sewage

Polluted by sewage 6,726 hours in 2026 so far..

Ynys Môn - Live Sewage

Which Year?

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View Annual Sewage Data

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Constituencies near Ynys Môn

Daily Data

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Totals so far

Data Sources & Accuracy

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It's a Dirty Business

Ynys Môn - Live Sewage Polluted by sewage 6,726 hours in 2026 so far..

Ynys Môn - Live Sewage

Which Year?

Select Another Constituency

View Annual Sewage Data

Take Action

Constituencies near Ynys Môn

Daily Data

We need your support!

Totals so far

Data Sources & Accuracy

Media Queries

Please Support Us

Ynys Môn - Live Sewage

Polluted by sewage 6,726 hours in 2026 so far..