with UK water companies, and supply chain partners to strengthen the UK water sector’s capacity for resilient and reliable sewer rehabilitation
WRc Group partnered with leading UK water companies and key suppliers across the sewer-rehabilitation sector to create a new infiltration test specification that defines what constitutes a truly leak-free sewer repair. This initiative addresses growing industry concern about groundwater infiltration, a major contributor to discharges from combined sewer overflows (CSOs). With AMP8 driving increased sewer-renovation investment, the sector needed a modern, reliable, and standardised approach to verifying the performance of Cured-In-Place Pipe (CIPP) lining systems.
with UK water companies, and supply chain partners to strengthen the UK water sector’s capacity for resilient and reliable sewer rehabilitation
a new methodology for verifying the infiltration resistance and leak-tightness of CIPP sewer liners, including end seals and lateral connections
a new fit-for-purpose infiltration test methodology that clearly defines what constitutes a leak-free sewer repair
Groundwater infiltration is one of the primary causes of CSO spills, placing pressure on ageing sewer networks and increasing regulatory, environmental, and customer-service risks. Although existing standards—EN 752:2017, BS EN 13380:2001 and WRc’s SRM Type 2—require leak-tightness, none offer a clear methodology for testing infiltration resistance. Water company experience showed that some CIPP products in the field did not consistently prevent infiltration hence a specification for leaktight lining products was required.
Furthermore, many products assessed under the historic CP308 test (2008) are no longer available, and the sewer-rehabilitation market has evolved substantially. Without an updated, comprehensive, and industry-backed testing framework, water companies lacked confidence in the long-term performance of liners to be used during AMP8 programmes.
The Solution
A collaborative project was launched bringing together multiple water companies, a government body, and a range of major supply chain partners across the industry.
Building on the principles of CP308, the team designed a robust, modernised infiltration test methodology that reflects the materials, construction techniques, and system requirements of today’s sewer-lining market. Key innovations included:
Extensive physical testing was undertaken, ensuring the methodology was practical, repeatable, and applicable to a wide range of lining products. The new methodology will be formalised as a Water Industry Specification (WIS) 4-34-07 and has the potential to form the basis of a future BS EN standard.
WRc will continue providing independent product verification, either as standalone testing or through the WRc Approved scheme, enabling manufacturers to demonstrate compliance to UK and international markets.
The Outcome
The project has delivered the first industry-wide, fit-for-purpose specification for assessing the infiltration resistance of CIPP liners. This gives water companies:
Suppliers now have a clear standard against which to test and validate their products, supporting innovation and ensuring consistent, high-quality performance across the market.
By addressing a long-standing gap in testing standards, the new methodology strengthens the UK water sector’s ability to deliver reliable, resilient, and environmentally compliant sewer-rehabilitation outcomes.
Scott Weston
IMR Water Recycling Alliance