It's a Dirty Business

Watch Channel 4's documentary about the state of the water industry, then sign the petition to bring water back to public ownership.

Dorking and Horley - 2025 Sewage

Polluted by sewage 3,021 hours in 2025 , monitoring offline 4,508 hours , potential overflows 2,841 hours

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

Which Year?

Select Another Constituency

Select the constituency from the drop-down
✔ means we have live data (𝑥 if not)

View Annual Sewage Data

You're looking at the totals that we have calculated for sewage in Dorking and Horley 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.

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.

Take Action

Your local MP is Chris Coghlan (Liberal Democrat) - Find out more about their interests, donors, and voting at They Work For You

Share this page, post a message, and tell others about the huge problem of sewage pollution across the UK
Post
Post

Constituencies near Dorking and Horley

Daily Data

Jan - 1,145 hours , 800 offline
Feb - 634 hours , 58 offline
Mar - 29 hours , 304 offline
Apr - 4 hours , 273 offline
May - 61 hours , 121 potential
Jun - 16 hours , 367 potential
Jul - 47 hours , 585 offline
Aug - 15 hours , 640 potential
Sept - 40 hours , 720 potential
Oct - 145 hours , 744 potential
Nov - 137 hours , 248 potential
Dec - 744 hours
Daily data is experimental and data is not guaranteed to be accurate. Please inform us of any issue, we will fix.
Please note: We don't have rainfall data for Wales. If you know where to source it please let us know!
We need your support!

Please consider a one-off or small recurring donation. We need your help to keep this site going.

Donate Now

Totals so far

Company Site Name Receiving Waterway Overflow Days Total Duration (hours) Offline/Potential Pollution
Thames Water Holmwood STW Holmwood Stream 40 524h -
Thames Water Horley (Surrey) STW Mole 35 500h 15m 2,353 h
Thames Water Holmwood STW Holmwood Stream 17 295h 15m -
Thames Water Dorking STW River Mole 20 257h 45m -
Thames Water Stonebridge sso, brockham River Mole 22 240h 488 h
Thames Water Ironsbottom STW River Mole 21 229h 1,256 h
Thames Water Horley (Surrey) STW Mole 18 226h 45m -
Thames Water Ironsbottom STW River Mole 13 116h 15m -
Thames Water Charlwood, surrey Mans Brook 17 114h 265 h
Thames Water Canfold Wood (Ewhurst) SPS Thornhurst Brook 12 73h 45m -
Thames Water Capel SPS Deanoak Brook 9 49h 45m -
Thames Water Ockley Road (Ewhurst) SPS Cobbler'S Brook 5 49h 15m 2,075 h
Thames Water Brockham Bridge XX SPS River Mole 5 48h 30m -
Thames Water Dorking STW River Mole 3 45h 45m -
Thames Water Charlwood, surrey Mans Brook 4 37h 15m -
Thames Water Castle Gardens (Dorking) SPS Mole 7 36h 15m -
Thames Water Salfords SPS Salfords Stream 6 24h 30m -
Thames Water Brockham Bridge XX SPS River Mole 2 23h -
Thames Water Spooks hill, north holmwood Tanners Brook 8 22h 676 h
Thames Water Stonebridge sso, brockham River Mole 3 21h 45m -
Thames Water Canfold Wood (Ewhurst) SPS Thornhurst Brook 3 15h 45m -
Thames Water Commonside (Leatherhead) SPS Bookham Brook 7 12h -
Thames Water Boxhill SPS Into Land 9 11h 15m 235 h
Thames Water Boxhill SPS Into Land 3 10h -
Thames Water Capel SPS Deanoak Brook 3 9h 45m -
Thames Water Ockley Road (Ewhurst) SPS Cobbler'S Brook 1 6h -
Thames Water Spooks hill, north holmwood Tanners Brook 1 5h 45m -
Thames Water Castle Gardens (Dorking) SPS Mole 1 5h 45m -
Thames Water Salfords SPS Salfords Stream 1 5h -
Thames Water River Lane (Leatherhead) SPS Mole 3 5h -
Thames Water River Lane (Leatherhead) SPS Mole 0 0h -
Thames Water Commonside (Leatherhead) SPS Bookham Brook 0 0h -
Thames Water Dean Oak Lane (Leigh) SPS Deanoak Brook 0 0h -

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.

Top of the Poops

Analysing sewage pollution by the Water Industry

Follow on Instagram

Media Queries

Get in touch if you have queries or want to discuss our data.

press [at] top-of-the-poops.org

Please Support Us

We rely on donations to fund our work. Please support us if you can
Yes! Support TOTP!

© 2020-2025 Top-Of-The-Poops CC-BY-SA 4.0,
© 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

Some data reproduced under Open Government Licence

Please don't scrape these pages - we can maybe share our data with you

Full Copyright information available at: our GitHub page