South West Water has reduced storm overflow spills at its top spilling site in the village of Salcombe Regis in Devon after making improvements to remove misconnections and boost its treatment capacity.
In 2024, the storm overflow at Salcombe Regis Sewage Treatment Works was operating every day, and South West Water knew it needed to act.
Wastewater engineers investigated how the network was behaving to understand what was adding extra water to the system.
Monitoring showed that, in addition to surface water from rainfall entering the network, there were significant misconnections adding extra water into the sewer system.
Misconnections occur when rainwater drainage or other surface water flows are connected into the foul sewer instead of a separate surface drain, increasing the volume entering the network.
South West Water found that several misconnections in the Salcombe Regis catchment, including highway gullies with extensive road run-off, were carrying water straight into the sewers.
This extra water had been dramatically increasing the levels in the network and causing the storm overflow to operate.
Engineers also found that water held in the surrounding soil was entering the sewer network – a process known as groundwater infiltration.
Work has been completed to reduce this infiltration by relining sewers and sealing manholes to remove additional flows from the network.
From January to August 2025, before works to make improvements were completed, the area continued to be impacted by these additional flows, resulting in 213 spills at Salcombe Regis.
A key turning point came in August 2025, when the team removed some misconnections and installed a new wastewater treatment unit at the treatment works, tripling the site’s capacity.
Between September and December 2025, following the completion of the upgrades, spills at the site reduced significantly. During this period, the site recorded 11 spills, a 94% reduction.
Jenny Eamer, South West Water’s Operations Manager for Salcombe Regis, explained the thinking behind the upgrades.
“When more water enters the system than the treatment works can handle, it causes the storm overflow to operate.
“That can happen during heavy rain, but here we also saw water entering the sewers through misconnections and groundwater infiltration.
“By increasing capacity and tackling those misconnections, we’ve been able to treat far more wastewater and cut the number of spills. It’s a great example of how focused improvements like this can make a real difference to communities and the environment.”
The site is now more resilient, and work to tackle the remaining misconnections will continue throughout 2026.
South West Water continues to invest in storm overflow reduction across the region, committing around £760 million over the next four years.
The company aims to be the first in the sector to meet the government’s target of fewer than 10 spills per overflow per year by 2040 - a decade ahead of schedule.