Drinking water

Water from the Turitea catchment is of high quality, but not safe enough to use directly from the source. This is common in natural run-off from bush catchments.

Our treatment plant removes any colour, algae and silt, and ensures the water is free from bacteria and protozoans.

Water is chlorinated to neutralise some naturally forming tastes and odours caused by hydrogen sulphide. Fluoride is added at Turitea and at our bores. The level of fluoride in the water is maintained at between 0.7 and one part per million.

A local accredited laboratory keeps a close eye on the water quality from all our sources. Regular tests and samples are collected daily in different parts of the city for microbiological analysis.

The Turitea Stream has a catchment area of about 2,400 hectares. The average rainfall is 1,400 mm per year. This area is run under the Turitea Reserve Management Plan.

A reservoir has been formed at the lower end of the catchment by constructing a dam across the stream valley. The storage capacity of the dam is 1.7 million cubic metres – which meets the city's average daily use for about 60 days.

Turitea produces water quality equal to the best conventional plants in the world.

The plant was substantially upgraded in 1999 and most of its functions are now automated.

Manual tasks include monitoring production, maintaining and calibrating online technical instruments, and replenishing chemical stocks.

In times of peak demand, like weekday mornings, the main pipes from Turitea aren’t enough to supply the volume of water needed.

To meet this demand, we draw groundwater to boost mains pressure. It comes from wells, or bores, which are up to 250 metres deep. Each bore has its own pumping station. These pump drinking water through the network to your homes after it has been through a treatment process.

Under the New Zealand Building Code, water from the water network must not be able to return – or ‘backflow’ – to the system.

Backflow is dangerous when there is a cross-connection between a drinking water supply and a source of contamination or pollution. For example, a garden hose being left on in a bucket that has chemicals in it. 

There are cases where the public water supply has been contaminated with dangerous chemicals and other pollutants, causing illness. Simply because people weren’t aware of backflow.

How you can stop backflow

At home, you can reduce the risk of backflow by fitting an inexpensive hose tap vacuum breaker on outdoor hose taps. Available from your local plumber. 

Commercial prevention measures

Commercial buildings with potential hazards must have adequate backflow prevention.

This includes:

• hospitals and medical centres
• agricultural and horticultural operations
• points where portable water tankers are filled
• premises with boilers and cooling towers
• hairdressers and barbers
• some food preparation premises

If you’re not sure of the risks at your premises or business, call our Water Technical Officer on 06 356 8199.

Best practice: Backflow protection for hairdressing salons(PDF, 166KB)

Two-thirds of Palmy’s drinking water comes from our two Turitea Dams at the northern end of the Tararua Ranges.

The Upper Dam is a traditional concrete arch dam, which contains the bulk of our stored water. This dam then feeds the lower dam, which is an earth embankment style dam. It is the lower dam that feeds water to the Turitea Water Treatment Plant. It also maintains a constant flow to the Turitea Stream.

In 2001, we commissioned a small 200kW hydroelectric power station on the Upper Dam. Four turbines or generators are powered when water flows between the two dams. They operate at full capacity in winter – when the Upper Dam water level is consistently high. This generates enough electricity to power the entire treatment plant. Surplus electricity is sold back to the national grid.

In summer, the plant is switched to water-saving mode and most electricity is sourced from the grid. During these drier periods, water from the Upper Dam is only released to maintain the water level in the Lower Dam and a minimum flow in the Turitea Stream.

Some plumbing fittings have the potential to allow minute traces of metals to accumulate in any water standing inside them overnight.