The number of suspected illegal discharges of raw sewage into rivers and seas by water companies during dry weather increased significantly during the first five months of 2026.

Dumping raw sewage into waterways during dry spells via overflows amounts to pollution. It is considered a breach of the permits given to water companies and is illegal. Discharging during dry weather increases the toxicity of the sewage pollution entering waterways. Rivers have less flow and volume, and there is no rainwater to dilute the sewage pollution entering the waterway.

Last year, in what regulators said was tougher action on sewage pollution, water companies in England were for the first time required to report to the Environment Agency the number of times they discharged raw sewage from combined sewer overflows during dry weather. A dry day spill is flagged when an overflow operates despite little to no rainfall that day and the previous day.

In 2025, water companies in England and Wales reported 8,576 dry spill pollution discharges. But according to freedom of information requests submitted by Environment Agency whistleblower Robert Forrester, the pollution is getting worse, not better, despite the regulator’s promise of tougher action.

Between January and May this year alone, water companies discharged raw sewage into rivers and seas during dry weather 7,280 times. The data is comparable as it is based on the same instruction and taken from the same data recording system.

The water industry said the figures were as yet unverified and it was too early to describe them as dry spills.

Forrester, an Environment Agency officer for more than 20 years, revealed failures by the agency to take on water companies’ illegal practices before leaving his job.

“Dry day spills will almost always be deliberate and illegal, otherwise there would be non-stop raw sewage spilling from pipes,” said Forrester.

“The huge increase in a much drier year appears to show that water companies have quotas of sewage to dump and will do whatever the weather, and whatever the risk to the public and the environment. Making money is the primary focus.” He said the regulator was no deterrent to the actions of the water companies.

“This level of criminality shows that water companies do not believe they, or the government, will ever do anything meaningful to stop them.”

Combined sewer overflows are an emergency system designed to be used in extreme weather to relieve pressure in the sewage system. But decades of underinvestment by the privatised water industry have led to the outflows being used regularly to discharge sewage.

In the first five months of 2026, South West Water, which operates across Devon, Cornwall and parts of Dorset and Somerset, discharged raw sewage on dry days 1,299 times. This compares with 2,451 times during the whole of 2025.

Water companies are facing outrage across the country for discharging raw sewage via storm outflows in August following the first moderate spell of rain after more than six weeks of drought. Public mapped data revealed water companies including Southern Water and South West Water discharging raw sewage from storm overflows within hours of the first significant rain.

In the south-west, after weeks of drought, the company’s own data suggested it discharged sewage into rivers and the sea for a combined total of almost 300 hours in the third week of August.

Ed Tyldesley, a Liberal Democrat county councillor in north Devon, said the company’s own figures showed 664 separate spills across 184 sites despite just 16.5mm of rain across the south-west.

“They are using a storm system when there are no storms. It is unbelievable. The worrying thing is that this all seems to be getting worse,” he said.

Tyldesley said he had been told by the water company that its live monitoring data could sometimes contain false readings. “That leaves two possibilities. Either the South West Water data is correct and sewage was discharged into our rivers and seas for 299 hours in a single week, or their legally mandated monitoring system is so unreliable that hundreds of apparent sewage spills are being reported to the public, which may not actually have happened.”

A spokesperson for Water UK, the trade association for the water industry, said: “These are unverified figures, and it is too early to describe them as dry day spills. Nonetheless, no spill is ever acceptable. Water companies are working to end them as fast as possible by tripling investment. Companies are investing £12bn to halve spills from storm overflows by 2030, including relining and sealing sewers to prevent groundwater infiltration – one of the main causes of dry day spills.”

South West Water has said the company publishes near real-time monitoring data, which has to be validated before being used for regulatory reporting.

“Storm overflow activations can happen for a range of reasons and aren’t determined by rainfall figures alone.

“We continue to invest in our monitoring and are spending record amounts to reduce storm overflow use across the region. We’re reviewing the locations raised by the councillor so we can provide a full response.”

A Defra spokesperson said: “It is totally unacceptable that some water companies are failing to deliver value for money for customers and polluting our rivers, lakes and seas.

“After years of failure, we have taken immediate action to make water companies more accountable, and, for the first time ever, they are now required to report dry day spills as pollution incidents, providing the government with the evidence to go after water companies where performance falls short.”