Three major water companies have been accused of illegally discharging sewage on days when it was not raining.

A BBC investigation suggests that Thames, Wessex and Southern Water have all taken part in the practice, known as “dry spilling”, which is banned as it can lead to a higher concentration of sewage in waterways.

Water UK has called for the spills to be investigated.

Between the three companies, the BBC’s investigation suggests sewage was released in dry spills for 3,500 hours in 2022.

 

Companies are allowed to release sewage into rivers and seas in the UK in order to prevent pipe systems from becoming overwhelmed. However, it has to have been raining in order for it to be legal.

If it has not been raining, the sewage becomes less diluted and can lead to a build up of algae and toxins in the waterways.

Environment Secretary Therese Coffey told BBC News: 'It does seem extraordinary on the hottest day of the year that there may be releases. The EA is the regulator; they are the people who do the detailed investigation of why that has happened."

The BBC says that it requested information from the six other water companies in England, who all said they could not provide the information because they were already being investigated for potential illegal spilling by the EA and industry regulator Ofwat.

John Penicud, Southern Water’s head of wastewater operations, told The Independent: “We work with the Environment Agency and stakeholders to cut these so-called ‘dry spills’ – and all forms of water and wastewater releases.”

He added that “so called dry spells are a complex issue” and the company had to report some incidents as “spills” even if they were caused by rising groundwater entering pipes.

Responding to the BBC investigation, a Wessex Water spokesman said it only focused on these three companies “because other water companies refused to provide information.”

They added that the spills identified by the BBC were due to groundwater rising, and contested claims on other spills.

A Thames Water spokesperson said: “There are a number of methodologies for defining and calculating why and how dry day spills occur. The Environment Agency’s methodology for calculating dry day spills is still being determined and we will continue to work with our regulators as they define this.

“We regard all discharges of untreated sewage as unacceptable, and we have planned investment in our sewage treatment works... Stopping discharges altogether will take time and sustained investment, however each step we take on this journey is a move in the right direction.”