The duration of sewage spills into England’s rivers, lakes and seas almost halved last year, reaching the lowest level ever recorded.
Raw sewage was discharged for about 1.9 million hours in 2025, down by 48 per cent on the year before. Regulators called the fall “a clear win for people and the environment” but ministers said the level remained unacceptably high.
There were huge differences between water companies, with some cutting the duration by 40 per cent and others as much as 70 per cent. The Environment Agency, which published the data on Thursday, said the weather was the main reason for the dramatic decline rather than improvements by companies.
England experienced a very wet 2024, triggering a record length of sewage spills. However, 2025 was the driest spring in more than half a century, with widespread drought, meaning a huge swing from one extreme to another.
The figures are strongly influenced by the weather because heavy rainfall is typically what triggers sewage dumping from about 14,300 outfalls known as storm overflows.
The figures represent the lowest absolute number of spills since officials started releasing data in 2020, though complete monitoring of all the overflows was only achieved at the end of 2023. The average number of spills per overflow was also the lowest yet, down from 31.8 in 2024 to 20.5 in 2025.
The water industry has boasted of spending a record £104 billion between 2025 and 2030, with £12 billion allocated for tackling the sewage discharges.
However, the Environment Agency said such improvements were only just getting under way and were a minimal reason for the fall last year. It said the weather was the overriding factor, and its internal modelling supported that view.
“It is good to see that storm overflow spills are down since the previous year, but there is still an unacceptable amount of sewage entering our waterways and a long way to go in cleaning up our rivers, lakes and seas,” Emma Hardy, the water minister, said.
Under the government’s storm discharge reduction plan, the 2050 target is for overflows to operate an average of no more than ten times per year — a level where they are considered to have been effectively halted. In 2025 just under half of storm overflows met the target.
While most of England experienced dry conditions last year, Cumbria, Devon, and Cornwall had slightly above-average rainfall. That led South West Water to report a smaller cut in spills than firms further east, including Southern Water, Anglian Water, Wessex Water and Thames Water.
Those companies historically struggle with groundwater creeping into their sewage networks. Because the summer of 2025 was exceptionally dry, groundwater levels were unusually low, significantly cutting the number of discharges.
The absolute number of sewage spills fell 35 per cent to 291,492. The fall was even steeper than the roughly 25 per cent decrease suggested by sources this week before final validation of the figures.
“While these numbers are heavily influenced by rainfall levels in 2025, substantial reductions in spill duration and events are a clear win for people and the environment,” said Alan Lovell, chair of the Environment Agency.
James Wallace, chief executive of the charity River Action UK, said the dry weather meant lower spills “were inevitable, not evidence of real change”.
A spokesman for Water UK, the industry body, said: “Sewage spills are awful and we are working to end them as fast as we physically can. While the dry weather in 2025 will have led to fewer spills, we are also starting to see the effect of a tripling of water company investment.
“By building bigger storm tanks and expanding capacity at sewage treatment works, we will halve spills over the next five years.”
The Times recently revealed that about 15,000 of the spills last year were almost certainly illegal, as they happened on dry days. Its Clean it Up campaign is calling for stronger regulations to improve Britain’s waterways, as the government prepares to pass reforms for the water sector.
