Thames Water

was responsible for at least 16,990 sewage overflows in 2023
On average 46.5 times a day

These lasted for 196,414 hours (That's 22.73 years!) - in 494 different locations across their service area

Thames Water has 12 CSOs dumping sewage right now

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

1. CSO AT UPPER RICHMOND ROAD

Richmond Park into Beverley Brook

Started 2 months ago

2. Chesham

Chesham and Amersham into Chess

Started 2 months ago

3. Wealdbridge, North Weald

Brentwood and Ongar into Cripsey Brook

Started 1 month ago

4. STEWKLEY WASTEWATER TREATMENT WORKS

Buckingham into Hardwick Brook

Started 1 month ago

5. WINTERBOURNE WWTW

Newbury into Winterbourne Stream

Started 1 month ago

6. MARKYATE WASTEWATER TREATMENT WORKS

Hemel Hempstead into River Ver

Started 1 month ago

7. CUDDINGTON WWTW

Buckingham into River Thame

Started 3 weeks ago

8. South Moreton

Wantage into Mill Brook

Started 3 weeks ago

9. CLANFIELD WWTW

Witney into Halfacre Brook

Started 2 weeks 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

2023 - 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.

2023 - 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

2023 - Worst Locations Thames Water

1. FAIRFORD STW, FAIRFORD, GLOS

The Cotswolds polluted for 3,391 hours, into River Coln

162 incidents

That's 4.71 months.

3.1 times a week, on average

2. MORTIMER (STRATFIELD MORTIMER) WWTW

Wokingham polluted for 3,304 hours, into Foudry Brook

150 incidents

That's 4.59 months.

2.9 times a week, on average

3. STEWKLEY WASTEWATER TREATMENT WORKS

Buckingham polluted for 3,166 hours, into Hardwick Brook

162 incidents

That's 4.4 months.

3.1 times a week, on average

4. CLANFIELD STW, CLANFIELD, OXON

Witney polluted for 3,156 hours, into Halfacre Brook

150 incidents

That's 4.38 months.

2.9 times a week, on average

5. CIRENCESTER WWTW

The Cotswolds polluted for 2,870 hours, into Shorncote Ditch

165 incidents

That's 3.99 months.

3.2 times a week, on average

6. BURGHFIELD STW, BURGHFIELD, BERKS

Wokingham polluted for 2,861 hours, into Clay Hill Brook

132 incidents

That's 3.97 months.

2.5 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.