Thames Water sewage spills set for record high, despite inflation-busting bill hikes

Thames Water is on course to dump more raw sewage into its polluted rivers than at any time this decade, according to the stricken supplier’s own data.

The revelation comes as public anger about the state of the privatised water industry reaches boiling point after the TV drama Dirty Business highlighted the industrial scale of untreated effluent spewing into Britain’s waterways and wreaking havoc on the environment. It has led to renewed calls for the privatised water industry to be taken back into public ownership.

Thames Water, which is drowning in £20 billion of debt and is being kept afloat by creditors led by US hedge funds Elliott Capital Management and Silver Point Capital, is seen as the most vulnerable to being re-nationalised.

Latest figures show it has recorded almost 79,000 hours of sewage discharges so far this year – more than in any corresponding period since 2020.

The findings suggest that Thames Water’s creaking network of sewers, pipes and water treatment works was once again overwhelmed by recent heavy rainfall – despite the company promising to upgrade its wastewater system, which supplies 16 million customers in London and the Thames Valley.

Clean water campaigner and former Undertones singer Feargal Sharkey said he was ‘not surprised’ that Thames Water was ‘well on its way to beating its own record’ but ‘we should be outraged and appalled’.

Sewage discharges are allowed when it rains heavily because combined sewer outflows act as a ‘safety valve’ to prevent effluent backing up and flooding homes, roads and businesses.

But water firms have been criticised for also dumping raw sewage on dry days, which is illegal.

Thames Water was last year fined £123 million for breaching rules over sewage spills and dividend payments to shareholders.

Peter Hammond, ‘a former professor of computational biology at UCL, who was played by Jason Watkins in the Channel 4 docudrama, said it was ‘impossible to say’ how many of the latest spills were illegal based on available data.

But in a recent study, he found that Thames Water made at least 8,499 illegal discharges from its sewage treatment works between 2021 and 2025, representing 22 per cent of all spills.

Hammond’s report also found that some of the company’s sewage works were pushing effluent through too fast for it to be properly treated, meaning even higher levels of illegal pollution could be going undetected.

‘Thames Water’s continuing insolvency issues and [my] illegality findings are strong grounds for invoking a special administration regime,’ Hammond said referring to a temporary form of nationalisation.

‘Potential lenders providing a lifeline to the ailing Thames Water have demanded the company be spared prosecution for illegal sewage spills in order to ensure future funding.’

A spokesman for London & Valley Water, the creditor consortium, said there was ‘no such request and there will be no immunity from prosecution’.

In 2024, water companies in England discharged raw sewage into waterways for a record 3.6 million hours, according to The Environment Agency.

The average length of a spill at Thames Water was 13 hours, the highest of any supplier.

It comes as average water bills across England and Wales are set to rise by an inflation-busting 5.4 per cent to £639 a year from April. They have doubled in real terms since privatisation in 1989, when the industry was sold to shareholders debt-free.

Since then the ten water firms in England and Wales, which are monopolies with no competition, have racked up £60 billion of debt while showering shareholders with £85 billion in dividends.

More than a third of water bills are spent on servicing debt and paying dividends rather than fixing leaks and preventing spills, a recent analysis by the University of Greenwich found.

Thames Water said it was reviewing Hammond’s report and could not comment, but added: ‘Taking action to improve the health of our rivers remains a key focus for us and, over the next five years, we are delivering the most significant upgrade to our wastewater network in 150 years. Farming, industry, road runoff, wildlife, and increasingly extreme weather also play a role in river health.’