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Area of Outstanding Natural Beauty

Llyn - 2025 Sewage

Polluted by sewage 8,943 hours in 2025 - That's 1.04 years

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

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Totals for 2025

Sewage8,943 hours
Monitoring offline0 hours
Potential pollution0 hours
Storm overflows13

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Daily Data - when it rained, and when they spilled

Square = rainfall none → heavy
Drop = sewage minutes → all day
Potential pollution Monitoring offline
Jan - 0 hours
Feb - 269 hours
Mar - 73 hours
Apr - 152 hours
May - 70 hours
Jun - 83 hours
Jul - 42 hours
Aug - 26 hours
Sept - 553 hours
Oct - 606 hours
Nov - 2,980 hours
Dec - 4,059 hours

Storm overflows in and around Llyn

Company Site Name Receiving Waterway Overflow Days Total Duration (hours) Offline/Potential Pollution
Dwr Cymru Welsh Water Llanaelhaearn WwTW Overflow Unnamed Watercourse 197 1,923h 37m -
Dwr Cymru Welsh Water Trefor WwTW Relief Discharge Point Storm Overflow Unnamed Watercourse 124 1,651h 59m -
Dwr Cymru Welsh Water Nefyn Storm Overflow Caernarfon Bay 106 1,610h 28m -
Dwr Cymru Welsh Water Llithfaen WwTW Storm Overflow Rhyd Hir 78 1,552h 44m -
Dwr Cymru Welsh Water Lôn Goch Edern Storm Overflow Afon Geirch 60 681h 33m -
Dwr Cymru Welsh Water Llanbedrog Long Nant-Iago Storm Overflow Tremadog Bay 35 534h -
Dwr Cymru Welsh Water Nefyn WwTW Settled Storm Overflow Unnamed Tributary of Afon Geirch 25 327h 32m -
Dwr Cymru Welsh Water Clynnog Fawr Storm Overflow Unnamed Stream 54 313h 44m -
Dwr Cymru Welsh Water Aberdesach Storm Overflow Afon Desach 57 153h 11m -
Dwr Cymru Welsh Water Abersoch Harbour Storm Overflow Afon Soch Estuary 10 101h 17m -
Dwr Cymru Welsh Water Aberdaron Storm Overflow Afon Daron 20 53h 39m -
Dwr Cymru Welsh Water Trefor Storm Overflow Unnamed Stream 14 25h 44m -
Dwr Cymru Welsh Water Aberdaron WwTW Storm Overflow Afon Cylch-y-Felin 12 13h 59m -

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.