Drinking water

• Supply is available to all serviced properties 99% of the time.
• Flow at point of supply generally exceeds 15 litres per minute.
• Pressure at point of supply generally ranges from 20m to 60m static head. It is the pressure that forces water through the pipes.
• Water is treated with chlorine at Westmere and Kai iwi and with chlorine and ozone at Aramoho.
• Information is available on request to assist with locating pipes electronically through BeforeUDig. Onsite service / toby locations are also available on request.
• Ongoing maintenance and operation of the network and facilities ensures functionality and availability of service.
• Quality, quantity and pressure complaints and/or enquiries are responded to within 24 hours.

Services provided to rural users vary between schemes. Services provided to rural users vary between schemes.  You can find information about approved contractors here(PDF, 37KB) .

Mains flushing, hydrant flushing, scouring and aeration are essential parts of our routine maintenance programme and have the following benefits:

• Ensures fire hydrants and valves are working properly
• Removes sediments in water supply mains and improves water quality
• Helps to identify weaknesses in the water reticulation system
• Ensures different parts of the reticulation network can be isolated if required

In June 2023, a city-wide mains flushing was done throughout Whanganui to remove any sediment build-up as well as ensure the fire hydrants are operating properly. This work involved forcefully releasing water through the pipes via the hydrants.

City-wide flushing is a new initiative (usually this routine maintenance is done on a smaller scale, based on a particular suburb or grouping of streets) and is likely to become an annual event as continuous flushing helps maintain water quality. While the water entering the system is of very high quality, it can deteriorate ie with sediment build-up, so it’s best to clean out the mains on a regular basis.

During the flushing, the hydrants are open for between 15 and 20 minutes. It’s recommended that you don’t use your washing machine or dishwasher during this time if possible. More information under the 'discoloured tap water' section.

There are no restrictions on the use of automatic garden sprinklers. Hand-held hoses can also be used at any time.

We are committed to ensuring all our supplies provide safe drinking water that is compliant with the quality assurance rules issued by the drinking water regulator Taumata Arowai. 

We test for a range of microbiological contaminants (E.coli, total coliforms), chemicals (chlorine, metals, nitrates etc) and physicochemical parameters (pH, conductivity) in the source and treated water and in the reticulation network. This helps the operations team to make decisions about how they operate the treatment plants and any changes or potential upgrades that might be required. 

We report on the performance of our water supplies to Taumata Arowai regularly (monthly, 3-monthly and annually). If something goes wrong (i.e. contamination found or people in the community are getting sick) Taumata Arowai may become involved in the council's response – by issuing instructions or sending its representatives to Whanganui.

Find out more about where, when and what we test(PDF, 503KB) 

Chlorine is a disinfectant that kills many water-borne bacteria and viruses that could cause sickness and diseases. Our water supply bores are deep and less vulnerable to contamination at the source, however contamination can occur as the water is delivered to your home through underground pipework.

Chlorinating the water as it leaves the treatment plant provides a protective residual in the water to kill any bacteria and viruses which could enter the water through broken pipes or back flow from private connections.

We dose chlorine at a concentration of around 0.5 to 0.8 milligrams per litre of water (0.5 parts per million parts) to ensure the residual remains throughout the extent of the reticulation network. Taumata Arowai require a minimum chlorine residual of 0.2 milligrams of chlorine per litre of water to provide protection in the network. The New Zealand drinking water standards allow a maximum of 5 milligrams of chlorine per litre of water (5 parts per million parts) to prevent any adverse health effects over a lifetime of consumption.

The chlorine concentration in the treated water is measured by calibrated instruments at one-minute intervals 24-hours a day and seven days a week. The chlorine concentration is monitored every day by our operational staff and alarms will notify them (day or night) if the chlorine is approaching a high or low limit so they can take immediate action.

If the water coming out of your tap becomes discoloured (brown / yellow) this is most likely caused by sudden changes in the direction or flow of water in the reticulation dislodging sediment that has accumulated in the pipes over time. The changes in flow or direction are due to regular activities such as re-instating flow after maintenance or repair work, regular flushing activities or high flows due to firefighting activities.

Where possible the council will notify you if planned work is being carried out in your area (by leaflet drop and other methods) and advise you of the actions to take when the water comes back on. Discoloured water is generally safe but may stain clothes, so we would recommend waiting until the water is clear before putting on a load of laundry.

If your water is discoloured, run the OUTSIDE tap for 10-15 minutes to see if it clears.

If it doesn't clear, please report it by calling our 24-hour phone line: (06) 349-0001.

If the water is cloudy, white or milky in appearance this is likely caused by air trapped inside pressurised pipes after maintenance or repair work.

If your water is cloudy, allow the water to stand in an open container and it will become clear after a few minutes. The bubbles will clear from the bottom upwards.

Again, if it doesn’t clear, please report it to usl on our 24-hour phone line: (06) 349-0001.

Whanganui’s water is considered 'hard' because it is relatively high in dissolved minerals such as calcium and magnesium. The water becomes hard because of the path it takes from the surface down and through the underground aquifer. It picks up minerals as it moves through layers of soil, rock and shell.  Hardness is not a risk to health and at approximately 175 mg/L (as CaCO3) in the Whanganui supply, is within guidelines limits set by the drinking water regulator Taumata Arowai.

Hardness can, however, become a nuisance when it causes scale on elements and plumbing fittings and water stains on surfaces.

If hard water has caused scale and water stains, here are some handy tips (please check the manufacturer's recommendations before cleaning):

• Soak the inside of your kettle in vinegar and then rinse well before use. If the build-up is thick, you may need to repeat this several times. Same for your steam iron
• For taps and shower heads, soak an old cloth in vinegar and then wrap it around the tap/shower head and leave it for two or three hours, then remove and rinse. Repeat if necessary. • Stains on glassware, tiles, showers: wipe with a vinegar-soaked cloth, then rinse
• Brown staining (caused by Iron) can be removed by using Epsom salts or other readily-available products.

All water supplies in New Zealand are assumed to be plumbosolvent meaning the water is capable of dissolving trace amounts of heavy metals such as lead and copper out of some household plumbing and fittings.

Although the health risk is small, we recommend 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. This simple precaution is recommended for all households, including those on public and private water supplies.

A boil water notice is an instruction, put in place by a water supplier when the drinking water supply contains, or could contain, bugs or microorganisms that could make you sick. Boil water notices are put in place when E. coli is detected in the water or when the supplier has identified a risk of contamination such as a problem with the treatment system or damage to pipework.

If the council does issue a boil water notice, details of the affected areas and what to do will be widely available on the council's website, social media channels, Antenno and via Whanganui media outlets.

A do not drink water notice is issued when the water supply is, or could be, contaminated with harmful chemicals and toxins. In this case boiling water will not make it safe.

If the council does issue a do not drink water notice, details of the affected areas and what to do will be widely available on the council's website, social media channels, Antenno and via Whanganui media outlets.