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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).

Water Renewals

Water main and connection renewals have been programmed over the next ten years at a total cost of $19.9 million. This sum includes replacement of a trunk main into town that will be staged over the first five years of the plan at a total cost of $7.6 million. Depreciation reserves will only cover some of this work, so some loan funding is also required. Loan servicing and repayment will be funded by urban ratepayers. This work is consistent with our asset management plan and is based on cost-effective management of the asset now and in the future.

Urban Water Consents

Until now, our summer urban water restrictions have enabled us to stay within our resource consent limits for taking water from the Waingawa River. We expect that future resource consents will reduce the amount of water that we can take from the river during times of low flow. To meet future consents, we expect we will need to install water meters on all users – scheduled for 2019-20, costed at $3.4 million and construct larger untreated water storage dams – scheduled for 2026-27, costed at $7.2 million. It is expected that these costs will be funded by loan with costs spread across the users over the period of the loan.

Water meters have been shown to be the most effective way of reducing water use, reducing demand by around 30%. Water meters would also enable us to measure more accurately the difference between the amount of water leaving the treatment plant and the amount recorded by meters, that can assist us to detect and fix leaks in the system. Introducing water meters may mean we can avoid placing further restrictions on the use of water on gardens. Alternatively, instead of water meters, we could impose more stringent water restrictions in the summer.

Until the Natural Resources Plan is fully implemented, the water treatment plant upgrade timetable and scope creates significant uncertainty for us. The Natural Resources Plan may be more accommodating of urban residential and commercial needs for water during periods of low flow, and we may be able to gain dispensation to continue to meet commercial needs. However, if not, the principal alternative is to restrict supply to commercial users at times of low flow in the rivers. This contradicts our Economic Development Strategy that plans to encourage business.

Rural Drinking Water Supplies

The Ministry of Health has introduced higher standards for rural drinking water suppliers. We expect this will require improvements to infrastructure and treatment systems, and their ongoing maintenance, so that all rural systems comply with potable (drinking) water standards. A provision of $374,000 has been made to assist rural schemes in meeting these standards. It is expected that these upgrades will be funded by loan and costs spread across the users over the period of the loan.

The alternative to meeting drinking water standards is to close the rural water supply schemes, especially those that will cost more than users are willing to invest to meet the required standards. Closure would, however, impose higher costs on individual users to source water for personal and farm use, and may have a higher environmental impact than a group scheme.

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