South West Water is lifting the lid on the work its dedicated teams do every day to identify and tackle drainage misconnections across the region.

A hidden cause of pollution, misconnections occur when wastewater from a property is incorrectly connected into a surface water drain instead of the foul sewer system – meaning wastewater can enter watercourses without being treated.

Misconnections are hard to spot as they are hidden plumbing mistakes in people’s homes.

Pollution alerts, which are often reported by the public, are one of the first clues that something may not be right in the network.

In 2025, South West Water responded to 1,421 pollution alerts across the region, each requiring investigation.

Pollution Technician Cat Chappell is part of the team that responds to these and carries out investigations on the ground.

“When a pollution alert comes in, it isn’t always clear what you’re dealing with,” Cat said. “Not every alert turns out to be a misconnection, but they’re what we use as the starting point to find out what’s happening.”

For Cat, every investigation begins by gathering as much information about the area as possible before the team goes to site.

“I look at network maps, drainage records and any previous work order history to help me to build a picture of the area,” Cat explained. “It gives me a starting point to go from but doesn’t tell me the full story.”

When she arrives at a suspected pollution site, Cat begins by assessing what she can see.

“I look for signs like unusual discharge into a watercourse such as fatty substances, sewage related debris or changes in the colour or smell of the water” she said. “Anything that suggests water is going where it shouldn’t be.”

An example of a pollution in a watercourse.

From there, Cat then works to build an understanding of what may be happening and follow the flow of water through manholes, outfalls and watercourses to see if she can identify any issues.

“I check everything and try to narrow it down step by step to understand the cause of the pollution so we can address it as quickly as possible.

“Sometimes it’s clear quite quickly whether there has been a misconnection but often it takes time as they can be difficult to find.”

As investigations progress, Cat explained that some cases require further detail to understand how the drainage system is connected and where the issue may be coming from.

“If we think the pollution is due to a misconnection but we need more detail to be able to tackle it, we work with specialist contractors for support ” Cat said.

“The contractors then carry out CCTV surveys of the network in the area I’m concerned about to help us pinpoint the areas we need to look at further.”

When a potential misconnection is identified, Cat will contact the property owner to explain what has been found and request permission for further investigations, including dye testing.