DN250 Hydro-Generator Drain Relining
Recore was brought in to reline a DN250 drain line at the base of Maraetai Dam, servicing one of the hydro-generators.
The existing pipe sits beneath more than 20 metres of concrete, which meant digging it up or replacing it wasn’t really an option. It also needed to handle up to 40 metres of head pressure, so the repair had to be strong, watertight and built to last.
Access was one of the biggest challenges. The work was carried out in a confined space, with all plant and equipment moved to the work area by hand trolley. Access to the upstream end of the pipe was extremely limited, ruling out conventional lining methods that require equipment or access from both ends.
Recore developed a different approach, using UV-inversion CIPP lining, which allowed the team to install the new liner entirely from the accessible downstream end.
This meant there was no need to expose or disturb the existing pipeline beneath the dam structure.
The liner also needed to work around an existing 90-degree bend at the pipe's upper end. Specialist end seals were installed to provide a fully sealed finish and prevent water travelling between the new liner and the existing pipe.
What we did
- Relined a DN250 hydro-generator drain line
- Worked within a confined-space environment
- Installed the liner entirely from the downstream end
- Used UV-inversion CIPP lining
- Relined through an existing 90-degree bend
- Installed specialist end seals
- Completed the work without excavating or exposing the existing pipeline
- Planned the work around a critical generator shutdown window
The result
The drain line was successfully relined and returned to service without major excavation or structural works.
By adapting the installation method to suit the site, Recore rehabilitated a difficult-to-access piece of infrastructure while keeping disruption and generator downtime to a minimum.
A practical trenchless solution for a job where conventional methods simply weren’t an option.
