The brief
Affinity Water called us in to a leak on a 1200mm GRP water main inside Chertsey treatment works. 1200mm sits at strategic-main scale, and GRP (glass reinforced plastic) is its own thing to work with: rigid, brittle in the wrong places, and unforgiving of poor handling during exposure and repair.
The leak was inside a live treatment site, so every part of the job had to work around the operational constraints that go with that: protecting adjacent plant, managing site access, and keeping the wider treatment process running while the repair was carried out.
The challenge
The main was 6 metres deep. At that depth on a main of that diameter, excavation becomes a proper piece of engineering in its own right: shoring, dewatering if groundwater is present, safe access for the crew, and a working face wide enough to actually manage a 1200mm pipe. None of that is easy inside a treatment site where space is already tight.
Our approach
A 5 metre repair section was cut out and replaced. Working on GRP at this scale means careful exposure of the existing main, clean cuts, and jointing back to the parent pipe using methods that match the original material’s performance. The main was returned to normal service on completion.
- Main diameter
- 1200mm
- Material
- GRP (glass reinforced plastic)
- Asset class
- Strategic main
- Excavation depth
- 6 metres
- Repair section
- 5 metres
- Site
- Chertsey treatment works
- Client framework
- Affinity Water R&M
Outcome
Repair completed in challenging conditions, main back in service. First of two separate 1200mm jobs we’ve carried out for Affinity Water at Chertsey treatment works, followed by a 1200mm branch cut out on the same site in July 2024. See our broader water mains repair and maintenance work for water companies for context on how we approach strategic-main repairs.
