Most raw sewage spills in England may be illegal, according to new research that leans on a definition of "heavy rain" buried in secret court papers. UK law states that sewage should not be released during "normal" weather, but until now the regulator had not clarified what that meant — a gap campaigners say let the industry spill routinely with no consequences.
Campaigner Prof Peter Hammond obtained undisclosed documents from a court case against Southern Water for illegal spilling in 2021. They included a previously undisclosed definition of "heavy rain" conditions — the threshold above which water companies may legally spill. Using that definition, Hammond analysed more than 350 storm overflow outlets across all nine English water companies, serving more than 30m people.
His analysis suggests that for more than 80% of the time sewage was spilled, the weather was "normal" — making those spills potentially illegal. The water companies and the Environment Agency rejected the analysis and said they were working to reduce spill numbers. But the research intensifies pressure on an industry already under fire over the state of England's rivers, lakes and seas.
England's sewage problems stem largely from a system that mixes rainfall with household waste in the same pipes; when it rains and capacity is tight, the network overflows. Campaigners argue the lack of a clear rainfall threshold allowed routine discharges. With a damning review already urging stronger regulation, the findings add weight to calls for enforcement rather than promises.
If the analysis holds up, it could trigger a wave of enforcement. Water companies have long argued that spills are unavoidable during storms; Hammond's work suggests many occur in calm weather, where the law is unambiguous. Regulators face a choice between confrontation and quiet remediation. Either way, the secret definition is now public, and with it the means for campaigners, courts and customers to hold the industry to a standard it spent years avoiding.## Why it matters now
The findings arrive as the industry faces a damning independent review and growing political pressure to clean up. Campaigners argue that a clear legal threshold removes the excuse of ambiguity that companies have long relied upon. If regulators act, the result could be enforcement actions and fines that finally give the law teeth. For now, the secret definition is public, and with it the means to hold the industry to a standard it spent years avoiding.
With a damning review already urging stronger regulation, the findings add weight to calls for enforcement.
