Pipeworks used 400mm diameter thermoplastic polyurethane (TPU) hose as a bypass line to support their trenchless pipelining operation in the Western Hills area of Lower Hutt. Adapting technology used in the oil and gas industry, a more agile and reliable bypass was achieved which saved time, labour, and cost.

CCTV inspections revealed a 589m deteriorated section of a critical trunk sewer at risk of structural failure under State Highway 2 (SH2). Carrying around 300 litres per second of wastewater, it is vital regional infrastructure. To minimise traffic disruption, Wellington Water restricted the work to two weeks during the Easter school holidays. This demanded an innovative solution to quickly fix the pipe without shutting down the highway.

PipeWorks’ trenchless rehabilitation strategy included an Ultraviolet Cured-in-Place Pipe flexible liner that could be installed inside the old sewer and hardened in place with UV light. No major excavation work was needed as the liner could be pulled in through existing manholes. Over 589m of sewer main (including sections of 825mm and 675mm diameter pipe) was successfully relined under SH2 using this UV system.

At the same time, the team set up a robust bypass pumping system to keep sewage flowing. Instead of assembling hundreds of metres of welded rigid plastic pipe, PipeWorks deployed an innovative new thermoplastic polyurethane (TPU) hose solution. Long rolls of 400mm diameter TPU hose were laid out and linked with couplers, creating a nearly 900m temporary pipeline alongside the work zone. The TPU hose could handle about 8 bar of working pressure (with 24 bar burst capacity), easily managing the 300 L/s flow. Using the hose eliminated the 70+ joints and potential leak points that a standard polyethylene pipe setup would have required. This significantly reduced both time on welding and pressure-testing and the risk of leaks or delays. The TPU hose could be deployed and retrieved much faster than rigid pipe, and it performed flawlessly under high flow and pressure (tested up to 350–400 L/s) with no leaks.