23km of 1,575mm OD and 1,965mm OD concrete lined steel pipe

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Hunua 4 Water Main

Watercare’s new large diameter water main at Hunua was installed to cater for population growth and to increase the security of the water supply to
the Auckland region.

Now completed, the Hunua No.4 (Hunua 4) water transmission pipeline runs for 28km from Redoubt North Reservoir in Manukau Heights to Campbell Crescent in Epsom, connecting to the existing local water supply network along the way.

Steelpipe was awarded the contract to supply the pipe late in 2011 and the first 12m, 1,965mm diameter concrete lined steel pipes were manufactured in May 2012.

The spiral welded steel pipe is manufactured in compliance with NZS 4442:1998 and the steel is sourced locally from New Zealand Steel, complying with AS/NZS 1594. After welding, the pipes are 100% pressure tested and the hemispherical socket joint (HSJ) is formed. This joint allows easier installation and a slight deflection which, in some cases, reduces the need for fabricated fittings.

A new tape coating plant was commissioned to manufacture the 1,575mm OD and 1,965mm OD pipe which uses the Polyken® YGIII multilayer coating tape system. This is a highly effective, cold applied anti-corrosion system for in-ground pipelines. An anti-corrosion inner wrap and either one or two layers of outer wrap make up the secondary components of YGIII.

For the majority of the route, open trenching methods have been used to lay the water main, although in sensitive areas such as busy intersections, tunnelling or pipe bridges have been used.