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Polyweld NZ carried out the HDPE welding and fitting supply for a major wastewater pipeline expansion in Rolleston — 20km of 355mm SDR13.6 PN12.5 pipe plus a further 7.5km of 125mm pipe, designed by Beca. It was the largest project in Polyweld NZ’s history, and called for full-face flanges, tees, stub flanges, backing rings, and saddles, all welded to the AS/NZS 4129:2020 standard.
Live tapping avoided a full shutdown, removing the need for round-the-clock vacuum trucking.
Service continued uninterrupted for more than 31,600 Rolleston residents.
Minimal excavation kept the project’s environmental footprint low.
Polyweld NZ’s first live tap at this diameter, completed without a hitch.
Close coordination between Polyweld NZ, Asmuss, and Plasson kept the project on track.
The new DN355 PE line needed to tie into an existing, live DN630 wastewater main without shutting the system down. The original design called for a 630×355 reducing tee joined by electrofusion welding — but a full shutdown would have meant running around 20 vacuum trucks continuously to manage the wastewater load, an impractical and costly approach.
Allows pressure testing before coring. The internal cold zone is removed afterward, leaving a connection that matches or exceeds the strength of the host pipe.
A PE-to-PE, full-face connection that avoids the risks that come with a PE-to-ductile-iron flange joint.
Carried out directly on the active DN630 main, with no interruption to service.
Plasson provided pre-weld training and on-site field support throughout the tie-in.
Operations Manager Leighton Read credited the project’s success to a specialised welding team able to respond quickly under pressure, backed by trusted partners in Plasson and Asmuss — a combination of technical know-how and strong partnerships that let the team take on infrastructure of this scale with confidence.
Leighton Read — Operations Manager, Polyweld NZ
Download the complete PDF for the full technical breakdown and project timeline.
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