Broken plumbing is causing “horrendous” levels of raw sewage and pollutants to be dumped into the Thames, a study has found.
A survey of London waterways found foul waste from toilets, sinks and washing machines was ending up in rivers without passing through sewage treatment plants.
The filthy water, ultimately carried into the Thames, is threatening aquatic ecosystems, say the researchers.
Poorly connected plumbing is said to be the chief culprit.
Joe Pecorelli, project manager for the Zoological Society of London (ZSL) estuaries and freshwater team, said: “We’re calling on home and business owners across the capital to have their plumbing checked for misconnections.
“We’re also asking local authorities to ensure the plumbing systems of new developments meet correct standards, and that funding is increased for industry-wide awareness schemes like ConnectRight.”
For the study more than 100 trained volunteers assessed 1,177 outfalls – drains that send surface water into rivers.
Signs of contamination including sewage fungus were found in 356 locations. For every kilometre of river surveyed, there were two to three polluting outfalls on average.
Mr Pecorelli said: “Approximately 600km of rivers and streams flow through Greater London into the tidal Thames.
“Together, these waterways represent an invaluable habitat for wildlife, from eels and water voles, to kingfishers and dragonflies.
“But a history of poor water quality, badly-designed flood defences and adaptations for navigation has prevented many of them from achieving their full ecological potential. As a result, just one of the 39 rivers in Greater London has so far qualified as having ‘good’ ecological status or potential.”
The findings are contained in a new report published by ZSL.
Debbie Leach, chief executive of the waterways charity Thames21, said: “There is a massive environmental accident happening across London, and it is devastating our rivers.
“But because it is happening day after day, it isn’t making the news. That has to change.
“Each day, more and more waste water pipes from our houses are being connected up to rainwater drains going straight into rivers, and the result is horrendous.”