Inadequate household plumbing is allowing “disgusting” human waste and pollution to enter London’s rivers and waterways.
Volunteer-led inspections of the capital’s small rivers, brooks and streams found dozens of examples of wastewater being discharged directly into local watercourses rather than the sewer system, as a result of plumbing faults.
For the past decade, the Zoological Society of London – which operates London Zoo – has run the Outfall Safari programme, training volunteers to patrol riverbanks and identify drainage pipes discharging household sewage into the city’s waterways.
Its latest snapshot survey found pollution from plumbing “misconnections” across the rivers 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 who is leading the programme, said the state of some of the natural watercourses is “pretty disgusting”.
“The Brent is a hotspot for poor water quality,” Ms Carbery-Tarrant said.
Raw sewage is being discharged directly into the River Brent
LDRS
“It is pretty disgusting to be honest,” she continued. “There are some pretty bad surface water outfalls that are polluting a lot of watercourse.”
The recent Outfall Safari audit of 22.4km of the River Brent identified 44 so-called “polluting outfalls” – a name for drainage leading into a waterway – among 123 inspected, prompting emergency alerts to Thames Water across 15 high-priority incidents.
While misconnections can be isolated to appliances in a single property, often following home improvements or renovations, they can also affect entire blocks of flats or even whole housing estates.
A full-time enforcement officer was appointed last month by City Hall to tackle misconnections across west London, following persistent pollution problems affecting the River Brent.
Conditions on the River Wandle, one of London’s most biodiverse rivers, were “not too bad compared to other catchments,” said Ms Carbery-Tarrant, but chronic misconnections remain an ongoing issue.
Of the 105 surface water outfalls inspected on the Wandle, 90 showed no visible contamination, but nine were actively polluting, including two severe leaks that triggered immediate alerts to Thames Water and the Environment Agency.
Elsewhere, the audit of the River Ravensbourne identified 18 polluting outfalls, six of which required emergency alerts.
Volunteers during the most recent Outfall Safari programme
ZSL
Volunteers also found 17 polluting outfalls on the River Pinn, with three severe incidents of contamination raised to Thames Water.
Thames Water also runs a Surface Water Outfall Programme, using dye tests and household surveys to identify misconnections along the capital’s rivers.
Its recent focus on the Wandle — a rare 12-mile chalk stream stretching from Carshalton to the Thames at Wandsworth — uncovered 77 household appliances wrongly plumbed into rainwater pipes across just eight properties on Wandle Road.
The Outfall Safari programme is not the only venture of its kind. A citizen-led group called Haringey Water Squad posts regularly about its investigations into the health of the River Moselle, a small and mostly-hidden waterway running through north London.
In a post on Instagram, the group said it had discovered sanitary waste and high chemical readings at the Moselle Brook in Lordship Recreation Ground, Tottenham.
“These findings point to a serious, and sadly widespread, source of water pollution: misconnected plumbing,” they said.
It can take years for a misconnection to be noticed.
Property owners are responsible for correcting misconnections once identified, but resolving them can be more complex when an entire block of flats is affected or residents move into a property unaware of the faulty connections.
Thames Water and the Environment Agency also play key roles in the fight against misconnections.
The water supplier uses containment measures, including floating barriers called booms , to limit the spread of pollution from known outfalls. It aims to investigate all pollution reports within two hours.
It also informs owners suspected of having misconnected properties of their responsibility to fix the issue. If a homeowner fails to correct a misconnection within the voluntary period – typically 12 weeks – Thames Water can refer the case to the local authority, which can serve statutory notices or carry out the work and legally recover the costs.
While individual property-level misconnections are generally addressed by Thames Water or local authorities, the Environment Agency also retains powers under environmental protection legislation to intervene or prosecute in cases of serious or persistent environmental pollution.