Plumbing faults send human waste into London rivers

Inadequate household plumbing is allowing human waste and pollution to enter London’s rivers and waterways. Volunteer-led inspections of the capital’s smaller rivers, brooks, and streams have identified numerous instances of wastewater being discharged directly into local watercourses instead of the sewer system, due to plumbing faults.

Outfall Safari identifies widespread pollution

The Zoological Society of London (ZSL), which operates London Zoo, has been running its Outfall Safari programme for a decade. The initiative trains volunteers to patrol riverbanks and identify drainage pipes that are discharging household sewage into the city’s waterways. The latest survey from the programme has found pollution from plumbing misconnections across several rivers, including the Wandle in south London, the Brent in north and north west London, the Ravensbourne in southeast London, and the Pinn in west London.

Ella Carbery-Tarrant, a project officer at ZSL leading the programme, described the condition of some watercourses as “pretty disgusting”. She noted that the River Brent is a particular concern for poor water quality, with many surface water outfalls polluting the water. An audit of 22.4km of the River Brent identified 44 polluting outfalls among 123 inspected. This led to 15 high-priority incidents prompting emergency alerts to Thames Water.

Misconnections can affect individual properties, often following home improvements, but can also impact entire blocks of flats or housing estates. A full-time enforcement officer was appointed by City Hall last month to address misconnections affecting the River Brent.

Wandle Road properties found to have misconnected appliances

While conditions on the River Wandle were described as “not too bad compared to other catchments”, chronic misconnections remain an issue. Of the 105 surface water outfalls inspected on the Wandle, nine showed contamination, including two severe leaks that triggered immediate alerts to the Environment Agency and Thames Water. Separately, Thames Water’s own Surface Water Outfall Programme identified 77 household appliances wrongly plumbed into rainwater pipes across just eight properties on Wandle Road.

Similar issues were found on the River Ravensbourne, where 18 polluting outfalls were identified, six of which required emergency alerts. The River Pinn had 17 polluting outfalls, with three severe contamination incidents reported to Thames Water.

Citizen groups also report pollution

The Outfall Safari programme is not the only initiative investigating river health. A citizen-led group known as Haringey Water Squad has been monitoring the River Moselle in north London. In a social media post, the group reported finding sanitary waste and high chemical readings in the Moselle Brook at Lordship Recreation Ground in Tottenham. They stated these findings indicate a widespread source of water pollution from misconnected plumbing.

Responsibility and next steps for misconnections

Resolving misconnections can be complex, especially when entire buildings are affected or new residents are unaware of existing faults. Property owners are responsible for correcting misconnections once identified. Thames Water aims to investigate all pollution reports within two hours and informs suspected owners of their responsibility to fix the issue. If a homeowner does not correct a misconnection within a voluntary period, typically 12 weeks, Thames Water can refer the case to the local authority. Local authorities can then issue statutory notices or carry out the necessary work and recover the costs. The Environment Agency also has powers to intervene or prosecute in cases of serious or persistent environmental pollution under environmental protection legislation.