What we're doing to minimise discoloured water in the city, and what to do if your water is discoloured.
Palmerston North residents sometimes experience discoloured water coming out of taps. This is for two reasons: the slightly high iron and manganese content in our water, and the city's aging water main infrastructure, which retains the built-up sediment in the pipes.
We're fighting the problem on a number of fronts.
Every year we clean the two main water supply pipes that gets water from Turitea Dam to Palmy homes and businesses, to ensure our city's water stays pristine. This process is called swabbing and usually happens in winter because we need to do it when the Manawatū River is in high flow.
We do this because the water from the dam is slightly rich in manganese. We remove most of this during the treatment process but over time the minimal remaining amounts can build up in the pipes. While this doesn’t affect the quality of the drinking water, it can cause it to become discoloured. Cleaning the pipes ensures this isn’t a problem.
The cleaning is done late at night when less water is being used.
In 2022, we plan to clean the pipe overnight on Wednesday 10 August.
We're also replacing the old cast iron pipes in the water main network with plastic ones.
Leave the cold tap running for 10 minutes to see if the water runs clear. If not then call us on 06 356 8199 and we will flush the pipes around your property. The discoloured water may stain clothes, so we advise postponing doing the laundry until the water is clear again.
Yes, you can still use water while we clean the pipes. We do this work at night so fewer people are using water. Try not to do your washing overnight though, as your clothes may be stained if the water is discoloured.
Some residents in Turitea won’t be able to use water, but those homes will have received a letter from Council.
The water that goes through these pipes came from our Turitea Dam. Manganese is a mineral that naturally occurs in rocks and soil. We remove almost all of it during the treatment process, but tiny amounts still get through. Over time that can build up in the pipes. We remove it to ensure the city’s water supply isn’t discoloured. The Ministry of Health has a health guide of manganese of less than 0.4mg/L. Palmerston North’s is 0.01mg/L and we test it often.
We start by shutting off certain valves (or doors) to the main pipe. This causes the water to be stuck behind these doors. We insert a giant sponge into the pipe. Then we open those doors and the pressure of the water pushes the sponge through the pipes. As it moves through the pipes it cleans them. Near the river, we remove the sponge so it doesn’t end up in our precious awa. The water and any sediment is then flushed into the Manawatū River. Our consent conditions have very strict rules about when we can do this work to ensure the effects on our river are as minimal as possible.