The process, known as 'swabbing', will take place between 6:00pm on Tuesday night and 3:00am on Wednesday morning when water demand is low.
"We carry out this procedure to reduce the likelihood of residents finding discoloured water in their homes," says Dora Luo, Water Asset Engineer, Palmerston North City Council.
The work is controlled by a resource consent so needs to be carried out when the Manawatu River flow rate reaches a certain level and the river water turbidity is high, so it is scheduled during the winter months when river levels are highest.
"The swabbing process involves pushing a sponge which is slightly bigger than the pipe diameter through the pipe. It dislodges any sediment that has adhered to the interior surface of the pipe walls," says water asset engineer Dora Luo. "We will isolate this trunk pipe to avoid the city water quality being affected. Doing this work at nigh time when water demand is low will also reduce the possibilities of discoloured water."
Residents, with the exception of those in the Kelvin Grove area, may find discoloured water during the swabbing process and up to 48 hours following it. As a precautionary measure, the Council advises residents to:
- Reserve plenty of drinking water for the night and the following morning.
- Minimise your water use during the swabbing night to avoid discoloured water getting into the pipe system within your property.
- Check water clarity before using hot water on Wednesday morning to stop discoloured water getting into your hot water cylinder.
- Check water clarity before running your washing machine to prevent discoloured water staining your washing.
- Run your cold water taps for up to 15 minutes. If you do find the water is discoloured after swabbing, and ring the Council on 356 8199 if water is still not clear.
The Council cleans two trunk water pipes annually, and cleans the two pipes separately.
Updates about the timing of the 'swabbing' will be posted on the Palmerston North City Council Facebook page and website at pncc.govt.nz. An update will also be posted on Wednesday 26 August.