The brief
Affinity Water called us in to a leak on a collar joint at Chertsey treatment works. A collar joint is a mechanical junction between two pipe sections, and when one starts leaking on a strategic main inside a treatment site, the constraints stack up quickly: live-service pipework, adjacent plant, and an operational site that can’t be taken offline.
The challenge
The leaking collar sat between two concrete thrust blocks. Thrust blocks are mass concrete anchors cast around pipework at bends and tees to resist the hydraulic forces generated when water changes direction under pressure. They’re deliberately enormous and deliberately immovable. The collar needed access; the concrete was in the way.
Standard excavation around the collar would have risked damaging the main itself. The answer was hydro blasting: a specialist technique using ultra-high-pressure water to cut and remove concrete while leaving the pipe intact. We brought in a specialist contractor to handle that specific element of the works.
Our approach
With the concrete carefully cut away and the collar exposed, the leak was encapsulated. Encapsulation involves installing a bolted-on repair collar around the leaking joint, sealing it against the parent pipe and stopping the leak without a shutdown of the main. The technique is fast, live-service, and well-suited to collar and joint failures where a replacement would mean taking the asset out of service.
- Technique
- Encapsulation
- Leak location
- Collar joint between two thrust blocks
- Specialist subcontractor
- Hydro blasting
- Site
- Chertsey treatment works
- Client framework
- Affinity Water R&M
Outcome
Leak stopped, main still in service, plant still running. One of three separate jobs we’ve carried out at Chertsey treatment works for Affinity Water. See our broader water mains repair and maintenance work for water companies for context on how we sequence specialist subcontractor work into R&M jobs.
