Every year since 2020, the Environment Agency has released data which shows the number and duration of so-called storm overflows, when a sewer overflows into a river, stream, lake or the sea because otherwise it would flood into streets and houses. This behaviour is by design, but now we know that this happens far more often than it should, especially in the north-west region served by United Utilities. Despite signs of improvement this year, upgrading the region’s water treatment system is going to mean higher water bills for decades to come.
Sewage seeps into the Archers
Sewage overflows have become a political issue. Campaigners such as Feargal Sharkey and Surfers Against Sewage keep the issue at the forefront of public attention. It has even become a storyline in the long-running Radio 4 programme The Archers. The Government has a ‘storm overflows discharge reduction plan’ and all the water companies have committed to major investment to solve the problem.
We pay the price
Fixing the problem is expensive and it is clear who is going to pay. In the north-west, United Utilities bills are rising rapidly: after an average 8% rise in 2024/25 they go up more than 25% for customers in 2025/26). People are infuriated that shareholders still receive hundreds of millions of pounds in dividends, and water company executives continue to be handsomely rewarded. Many people question the market model that sees privately owned companies making a profit from providing a fundamental human need – and incredibly in the case of Thames Water, losing so much money doing it that they risk financial collapse. Others point out that it’s not possible for a customer of United Utilities to switch to South West Water, so normal market mechanisms do not work.
What did we get for our money in 2024?
We now have five years of data for storm overflows. All 2270 United Utilities overflows are now monitored and the results published annually by the Environment Agency. The data include the number and duration of the times when the overflow is discharging. The charts below show that the number and duration of spills has followed the total rainfall in the north-west, until last year. The more rain, the higher the chance that the sewer will become overloaded.
Source: Environment Agency, charts by the author
Source: Met Office, chart by the author
Signs of improvement?
It appears from these charts that United Utilities made progress in 2024, as even though rainfall last year was similar to the year before, the number and duration of spills fell quite sharply. Indeed, the company claims:
“United Utilities’ multi-million-pound investment plan to reduce spills from storm overflows is moving at pace across the North West.”
“Despite another wet year in 2024 and nine named storms, official figures released by the Environment Agency (EA) have today confirmed the company’s annual event duration monitoring (EDM) submission reporting a 31% reduction in spill duration, with the number of spills from storm overflows falling by 20%. That’s 19,720 fewer spills compared to the prior year.”
However, it seems unlikely that the limited number of projects completed in 2024 could account for the reduction observed; there are 2270 storm overflows (as reported in the Environment Agency data, United Utilities themselves use a slightly lower figure) and only a handful could have been impacted by the projects highlighted by United Utilities.
How do United Utilities compare to their peers?
United Utilities appear to have improved the most of all 10 water companies if you compare 2024 to 2023.
Source: Environment Agency, charts by the author
Source: Environment Agency, charts by the author
Still a lot of work to do
However, despite this apparent improvement, they had more spills than anyone else in 2024, and were in the top three for duration of spills.
Source: Environment Agency, charts by the author
Source: Environment Agency, charts by the author
United Utilities’ planning extends over the next 25 years, with £3bn capital investment in the first phase to 2030. This is the highest amount among the 10 water companies in England, according to the national plan. They acknowledge it will take time and, for that reason, their good performance in 2024 looks odd – much better than can be explained either by rainfall patterns or by the new investments paying off.
A deeper dive into the sewage
The map below shows the 150 most improved storm overflows – accounting for about 85% of the total reduction in duration across the north-west.
Source: Environment Agency, map by the author
To illustrate the difficulty in getting a clear picture, in the far north of the region, near Carlisle, are two overflows that both reduced markedly in 2024 – in each case by more than 2000 hours compared to 2023.
Source: Environment Agency, map by the author
The Cargo wastewater treatment plant has benefited from the United Utilities investment programme. It’s actually featured on their website as a case study for the work they are doing – “we installed a new tank to provide temporary storage for spills and an additional storm tank to add a further 75m3 capacity.” Spills have been reduced to virtually zero. It’s genuine progress.
A few miles away, Newton Arlosh pumping station shows similar improvements. The duration of spills reduced from over 2300 to just 25 hours. While this is also good news, there’s no obvious reason for it – no investment was made and there was no unusual weather. There are many similar examples in the region.
Consumers face a future of rising bills
There was some positive news in the north-west in 2024, but the euphoria in United Utilities press release is overdone. Progress is being made, but there are 2270 storm overflows and about 500 wastewater treatment plants in our region. Expect many more years of rising water bills before this issue is truly fixed.
The National Audit Office has reported on the water industry recently and its conclusions make depressing reading: “The Department for Environment, Food and Rural Affairs (Defra) and water regulators have failed to drive necessary investment for the sector, which now faces significant environmental, supply and infrastructure challenges”.
To put in another way, in a drive to keep water bills low, regulators have allowed many years of under-investment. A growing population and climate change – more intense rainfall for example – has led to a slow decline in water quality. Making the duration and number of spills public is a great example of how transparency can enable citizens to monitor and to some extent change how the water companies and their regulators behave. But as this article shows, the picture that emerges from the data, like our water, is often cloudy.
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