Thames Water

was responsible for at least 23,061 sewage overflows in 2024
On average 63.2 times a day

These lasted for 298,080 hours (That's 34.5 years!) - in 525 different locations across their service area

Thames Water has 9 CSOs dumping sewage right now

Here are the ones that have been overflowing for the longest, without interruption

We are getting more data collated for each of the CSOs... right now we just have the Constituency. Unfortunately, the water companies use different names for the CSOs in their live data than in the annual returns, so it will take a bit of time to link all the data up....

1. ThW0146

Harpenden and Berkhamsted

Started 4 months ago

2. ThW0183

Didcot and Wantage

Started 13 hours ago

3. ThW0198

Brentwood and Ongar

Started 2 hours ago

4. ThW0229

Chingford and Woodford Green

Started 3 hours ago

5. ThW0232

Cities of London and Westminster

Started 4 weeks ago

6. ThW0240

Cities of London and Westminster

Started 3 weeks ago

7. ThW0391

East Grinstead and Uckfield

Started 2 weeks ago

8. ThW0461

Newbury

Started 2 weeks ago

9. ThW0805

Mitcham and Morden

Started 8 hours ago

How many Sewage Overflows are dumping sewage?

We have live data for Thames Water so we can track what happens every day - given that overflows are supposed to happen on an 'exceptional' basis only - does the chart indicate that?

The red line indicates the number of CSOs that overflowed for at least 30mins, the grey, the number of CSOs that were offline for at least 30mins, and the blue line is the total number of CSOs that we can get information for.

There is daily updated information on all constituencies covered by Thames Water

2024 - By Water Company

How does each water company compare? These are the totals by company for each. The totals are really high, counting things in hours doesn't make it very easy to think about. Here we show how many years of continuous sewage dumps happened in a single year, by water company.

2024 - Asset Spill Duration Comparison

It isn't like there are just a few outliers... the problem exists across the entire estate of water assets. Here we show a 'cumulative frequency diagram' - where the number of CSOs that dumped sewage for a time, or longer, is shown. You can see that many CSOs dumped sewage into a river for months and months.

Thames Water is highlighted in the plot below

2024 - Worst Locations Thames Water

1. South Moreton

Didcot and Wantage polluted for 5,353 hours, into Mill Brook

261 incidents

That's 7.43 months.

5 times a week, on average

2. WINTERBOURNE STW, WINTERBOURNE, BER

Newbury polluted for 5,062 hours, into Winterbournestream

219 incidents

That's 7.03 months.

4.2 times a week, on average

3. Amersham Balancing Tanks

Chesham and Amersham polluted for 4,842 hours, into Misbourne

210 incidents

That's 6.72 months.

4 times a week, on average

4. STEWKLEY WASTEWATER TREATMENT WORKS

Buckingham and Bletchley polluted for 4,482 hours, into Hardwick Brook

217 incidents

That's 6.22 months.

4.2 times a week, on average

5. CIRENCESTER WWTW

South Cotswolds polluted for 4,459 hours, into Shorncote Ditch

236 incidents

That's 6.19 months.

4.5 times a week, on average

6. BODDINGTON WWTW

Daventry polluted for 4,433 hours, into Boddington Canal Feeder

235 incidents

That's 6.16 months.

4.5 times a week, on average

Water Companies

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. This 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.