Sewer relining reduces spills by over 50% at Dulford pumping station after South West Water completed targeted infiltration reduction works at one of its highest spilling sites in Devon.
In 2024, the storm overflow at Dulford Sewage Pumping Station near Cullompton was among the region’s highest spilling assets. Following remedial works including relining 134 metres of sewer and sealing 11 manholes, spills fell by 53% in 2025.
Sewer relining reduces spills caused by groundwater infiltration
The primary driver of the excessive spills was groundwater infiltration — subsurface water entering the sewer network through defective joints and manholes. During prolonged wet weather, this additional hydraulic load can overwhelm local systems and trigger storm overflow operation.
Engineers carried out CCTV surveys to identify infiltration points within the network. A cured-in-place pipe lining was then installed, creating a watertight internal seal to prevent groundwater ingress. Follow-up inspections confirmed the integrity of the lining.
Groundwater infiltration is a significant contributor to inflow and infiltration (I&I) pressures across rural sewer networks, particularly in areas with shallow groundwater tables and ageing pipe infrastructure.
Jenny Eamer, Operations Manager at Dulford, said groundwater entering sewers increases system pressure during wet weather and that relining and manhole sealing had strengthened the network.
Part of £16 million infiltration reduction programme
Dulford forms part of South West Water’s £16 million Infiltration Reduction Programme, which targeted 175 high-risk sites following a review of performance across more than 1,600 storm overflows.
Infiltration reduction measures aim to:
- Reduce unnecessary hydraulic loading
- Increase sewer capacity headroom
- Lower storm overflow activation frequency
- Improve compliance performance
Utilities across the UK are increasingly focusing on network sealing and targeted rehabilitation as cost-effective alternatives to full asset replacement, particularly under AMP8 investment planning.
For more coverage on groundwater infiltration and wastewater network management, visit our Wastewater section.
