Drinking water

Water from the Turitea catchment is chemically high quality, but not high enough to use directly. This is common in natural run-off from bush catchments as the water is slightly coloured, sometimes has large numbers of algal cells, and after heavy rain may contain silt and protozoans such as Giardia and Cryptosporidium.

The treatment plant removes the colour, algae and silt, and ensures the water is free from bacteria and protozoans. Ongoing monitoring shows that the treatment plant provides an effective barrier to these issues.

The quality of the artesian supplies is excellent, with the only treatment required being chlorination to neutralise hydrogen sulphide that is present naturally, and to provide residual disinfectant protection in the reticulation.

Fluoride is added at Turitea and the artesian stations. The level of fluoride in the water is maintained at between 0.7 and one part per million.

The Council's laboratory maintains a close check on the water quality from all our sources. Bacteriological and general chemical quality is regularly tested and samples are collected daily in different parts of the city for microbiological analysis.

Flush water before drinking

Some plumbing fittings have the potential to allow minute traces of metals to accumulate in water standing in the fittings for several hours.

Although the health risk is small, the Ministry of Health recommends that you flush a mugful of water from your drinking-water tap each morning before use to remove any metals that may have dissolved from the plumbing fittings.

Palmerston North City Council backs this simple precaution for all households, including those on public and private water supplies.

The Turitea Stream has a catchment area of about 2,400 hectares, largely covered in bush. 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.

The plant is a full conventional alum-flocculation, rapid gravity dual media (pumice and sand) filtration type. It can also be operated in direct filtration mode during periods of low raw water turbidity, where the clarification process is by-passed.

The plant was substantially upgraded in 1999 and is now partly automated, requiring only one eight-hour shift a day to ensure a continuous supply. Most of the plant functions are automated with the manual tasks mostly being cleaning and calibrating equipment, and replenishing chemical stocks. Turitea now produces water quality equal to the best conventional plants in the world, with final water turbidity typically at 0.02 Turbidity Units.

In times of peak demand, like weekday mornings, the mains 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 artesian wells, or bores, which are between 300mm and 450mm diameter and up to 250 metres deep.

Each location has its own pumping station. The pumps are controlled automatically, starting when local pressures fall below set levels.

Under the New Zealand Building Code, water from the water network must not be able to return – or ‘backflow’ – to the system. Backflow can be especially dangerous if there is also a cross-connection between a drinking water supply and a source of contamination or pollution.

Backflow can happen as a result of something as simple as 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 injury and illness because people weren’t aware of backflow.

Residential prevention measures

At home, you can reduce the risk 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 whilst maintaining a constant flow to the Turitea Stream.

In 2001, we commissioned a small 200kW hydroelectric power station on the Upper Dam to provide electricity to the treatment plant located 2 kilometres downhill.

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 – and generate enough electricity to power the entire treatment plant. Surplus electricity is sold back to the national grid. Excess water is flushed via the Turitea Stream to the Manawatū River.

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.

In the year to March 2021, the total electricity generated at the hydro station was 2,107 gigajoules, while the total energy consumed at the treatment plant was 876GJ. This means we injected 1,230GJ back into the national grid.

Since February 2018, we have made more than $145,000 from selling electricity to the national grid.