TL;DR

Southern Water says machine learning running on its sewer sensors caught a blockage forming near the Lymington, a New Forest river, in time for a crew to clear it before sewage could spill into the water. The Bournemouth Echo reported the case on Thursday 8 October; the report does not say when the incident took place.

What happened

The Lymington runs for 13.5 miles through Hampshire before reaching the Solent, and is home to varied wildlife. When a sensor near the river picked up a blockage beginning to build, the control room was warned and sent a crew. They found wet wipes and other items that should not have been flushed. Had nobody noticed, sewage would have escaped from a manhole and run into the river.

The sensor is one of 34,000 that track sewage levels across the company’s waste network. The machine learning is the part doing the detective work. Daniel McElhinney, Southern Water’s manager for proactive operations control, said the system “learns the normal behaviour of sewers” and can separate the morning and evening peaks and rainfall from a genuine blockage. Instead of arriving after a spill, he said, teams can now clear sewers with high-pressure water jets before one happens.

In the past year, the company says, the system has led to more than 4,000 call-outs to head off trouble. After an alert, staff also call on nearby homes to explain what should and should not go down the drain.

A year on from Folkestone

This is not the first time the system has made the news. In September 2025 The Independent reported that Southern Water’s sensors had flagged unusual levels in a Folkestone sewer, where crews found a fatberg wrapped around a gym weight. Its sensor count then was over 34,000, the same scale it cites now.

Looking forward

The bigger obstacle remains what goes into the pipes. Each year Southern Water pulls roughly one billion wet wipes out of its pipes, and the average suburban sewer has the diameter of a tennis ball. Wipes containing plastic will be banned from spring 2027, but the company warns that wipes sold as “flushable” can still cause serious blockages.

In our view, this is a useful example for other UK utilities. The sensors are not new; the value comes from software that learns each sewer’s normal pattern, which lets crews be sent where a problem is forming rather than where one has already happened.