Just as the English water industry is requesting permission to further increase bills for both residential and business customers, another sewage discharge controversy has emerged that has the potential to complicate the already tempestuous transitional phase in the industry.
A report by the Bucks Free Press revealed that over 24 hours of raw sewage were discharged into two historic Buckinghamshire chalk streams in a single week in the middle of November 2025.
Two hours of this was in the River Chess running through Chesham, whilst a further 23 hours was in the River Misbourne running through Gerrards Cross, but both are the responsibility of the struggling Thames Water, which has been working on upgrades in the area to reduce the need to discharge sewage.
This has been blamed on Storm Claudia, but it has also tested the government’s new powers to crack down on the abuse of the use of storm overflow discharge systems and continued failures by water companies to protect the water supplies they are responsible for.
But why are UK water companies allowed to discharge sewage in the first place? How is it abused? And what can be done to stop the flow of effluent?
What Is The Sewage Discharge System?
Due to a sewage system that in parts dates back to Joseph Bazalgette and the Victorian age, much of the UK has a combined sewage system, which means that both clean rainwater and sewage wastewater travel through the same sets of pipes.
This is not true everywhere in the UK, and newer parts of the sewage networks use two separate pipes, but large parts of the country use this combined system, which is efficient at redirecting sewage, but because of the risk that the entire system backs up and causes potentially harmful spills in people’s houses, an emergency system was set up.
This system, known as storm overflow, allows for sewage discharges in situations where there is too much water in the system.
Whilst not an ideal solution, it is allowed in certain situations, usually when heavy rainstorms or floods risk causing significant harm. The logic is that in these situations, the raw sewage mixes with rainwater, diluting it enough to stop it from causing serious environmental harm when used occasionally alongside efforts by wastewater treatment works to clean up what they can.
However, whilst this is the way the system is designed, it is not the way in which the system has been used.
How Have Storm Overflows Been Abused?
The Environment Agency has a specific set of criteria for storm overflows that are acceptable, and an increasing number of reported incidents have created significant controversy that has led to extremely loud calls for reforms to the UK water sector.
The biggest offender has been the abuse of storm overflows, particularly when there are no storms. According to a BBC investigation, there were 6000 instances of dry spilling, a clear breach of permit conditions that implicated every water company in England.
The EA also condemns any storm overflows that cause visual impact due to the appearance of solid sewage or the development of harmful fungus, which infamously turned Lake Windermere green in 2022, as shockingly seen in images published by the BBC.
As well as this, damage to the biological and chemical makeup of the water, failures in bathing water quality standards, shellfish quality, coastal and transitional waters or pollution of groundwater are also condemned, something that is more likely with dry spilling.
Whilst part of the reason is straining historic infrastructure or misuse of drains by flushing solid matter down them, an alleged reason for dry spilling is that it is cheaper for water companies to discharge water illegally than to treat it.
What Can Be Done About Sewage Discharges?
Part of the problem has been long-delayed upgrades to historic infrastructure, which will help to avoid the need for storm overflows in the first place, and part of the solution will involve holding the companies that caused the issue accountable.
The ability to stop bad actors and punish harmful behaviour on both a civil and criminal level has been limited, something that has been aided by the passing of the Water (Special Measures) Act in early 2025.
This not only blocks bonuses for executives who pollute and opens the door to potential criminal prosecutions, but it also ensures that every sewage outlet is monitored so that Ofwat and the proposed organisation that is set to replace it have more information about where and when storm overflows are used.
There are options, but the issue is that some water companies want to raise bills in order to pay for it, which has been seen as rewarding failure.
