Drinking Water

Masterton’s Water Treatment Plant was opened in September 1983, and supplies a population of almost 20,000 mainly residential consumers. It is located about 10 km west of Masterton, on the north side of the Waingawa River, from which water is extracted for town supply.

Daily consumption varies from about 9 million litres per day during winter, to a high of 25 million in summer.


How is my water treated? 

Water is extracted from the river by siphon to draw the flow into a concrete main. This feeds the Water Treatment Plant 5 kms downstream. The flow is gravity assisted as it goes, with air being taken out of the pipe at several points along the line, to help maintain a full pipe.

Storage Ponds
At the treatment plant, raw (river) water is stored in three holding ponds until required. In the event of flooding and dirty river water, the flow can be shut off and the plant can run on its stored capacity for 3-4 days.

From the ponds, water is let into a large concrete vessel or clarifier, where the chemical coagulants PAC (poly aluminium chloride) and polyelectrolite are added to form small floc particles, which attract the fine suspended silt and clays present in the water. These drop to the bottom of the clarifier as sludge.

Five sand filters are used to “polish” the water to a high degree of clarity and remove any residual floc particles. The filtered water is then piped to a covered clear water pond.

Chlorine, Fluoride & Lime
Metered dosing is carried out at the clear water pond, using chlorine (disinfectant to give protection from micro-organisms which may enter the distribution system), fluoride (prevention of dental cavities in children), and lime (to raise the pH of the water making corrosion of pipes less likely).

The last storage point before water enters the town mains is the Upper Plain Reservoir, supplemented by smaller reservoirs on Lansdowne hill. The supply is almost all gravity fed from our reservoirs, with only a limited amount needing to be pumped to the highest point.


Fluoride free drinking water tap

Council also provides fluoride free water from a dedicated tap installed outside the Manuka Reserve in Manuka Street, Masterton. Details of the MDC and Opaki Water Scheme water supplies are available in the Assessment of Water and Sanitary Services 2018 (PDF, 5,585KB).


Using water during an emergency

Read more about ensuring your water is safe for use during an emergency (PDF, 2,142KB).


How do I ensure my private water supply is safe?

If the water your household drinks, bathes in and uses for food preparation comes from a private water supply, you are responsible for making sure that the water is safe for use.

This means if you have a ground water well, roof rainwater collection tank or get your water from a stream, river, lake or spring, you need to understand how to make sure it is safe.

Drinking unsafe water can cause illness (such as vomiting and diarrhoea). This can potentially be life-threatening for infants, the elderly or people with weak immune systems.

Visit the Greater Wellington Regional Council website to learn more about how to look out for your private water supplies.

You can also read more about private water supplies – testing and treatment (PDF, 355KB).

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