Could Your Home Be Secretly Polluting Cornwall’s Rivers?

Thousands of properties across the South West may be quietly sending untreated sewage straight into local rivers and streams, and most homeowners have no idea it’s happening.

South West Water estimates there are around 16,000 misconnected properties across the region, each one a potential source of pollution that can harm wildlife, damage water quality and affect entire ecosystems downstream.

What is a misconnection?

Most homes are connected to two separate drainage systems: a foul sewer, which carries wastewater from toilets, sinks and appliances to treatment works, and a surface water drain, which takes rainwater from roofs, driveways and roads directly to nearby rivers or streams.

A misconnection happens when these two systems are incorrectly linked. If a foul sewer pipe is connected into a surface water drain, untreated sewage can flow directly into local watercourses with no treatment whatsoever. The reverse problem, where surface water drains feed into the foul sewer, can overwhelm the network and trigger storm overflows.

Even a small misconnection can affect plants, wildlife and water quality in local rivers and streams.

The scale of the problem

In 2025, South West Water teams identified and worked to resolve 539 properties with misconnections, at a cost of over £200,000. While that represents significant progress, it is a fraction of the estimated 16,000 misconnected properties thought to exist across the region.

The team on the ground

Cat Chappell, South West Water’s Pollution Technician, is part of the team working to track down and resolve these hidden plumbing faults.

“To tackle these hidden plumbing issues we start by carrying out careful investigations in areas we’ve received reports of a pollution to check for debris, odours and discolouration in the water,” Cat explained.

Once a pollution is identified, the team reports it to the Environment Agency and takes water samples to assess the severity and identify the cause. From there, engineers use specialist cameras to trace contamination through the pipe network.

“They then contact those property owners to request access to do a dye test and further investigations to confirm whether they have a misconnection,” Cat said.

If a misconnection is confirmed, the property owner is informed and encouraged to fix the problem through a reputable plumber. It is worth noting that misconnections are classed as private issues, and the legal responsibility to put them right sits with the property owner, not the water company.

How misconnections happen

Misconnections are not always the result of careless work. They can occur when a property is first built, during home renovations such as adding an extension, or when plumbing is updated without drainage connections being properly checked.

“Identifying misconnections can be challenging as they are often hidden. That’s why working alongside our customers and the communities to do this important work is crucial,” Cat said.

What you can do

South West Water is asking residents to take a few simple steps to help prevent the problem from spreading.

Before any renovation or plumbing work, check your drains and use qualified, reputable tradespeople. If you are contacted by South West Water about a potential misconnection, cooperate with the investigation.

“Taking early action helps us to resolve these issues faster and helps us to protect the environment,” Cat added.

Residents can also help by keeping an eye out for signs of pollution in their local area, including:

• Fatty substances and sewage-related debris in streams or rivers
• Bright white foam or soap bubbles on the water’s surface
• Sewage fungus, which looks like grey, feathery growths on riverbeds
• Discoloured water near outfalls or surface water drains
• Detergent smells such as washing powder or laundry liquid near waterways

If you spot any of these signs, or want to find out more about misconnections and what South West Water is doing to address them, visit southwestwater.co.uk/misconnections.