The process, known as 'swabbing', will take place during the evening and early morning hours from 7:30pm to 3:00am when the demand for water is low.
"The swabbing this week is more complicated than the operation we completed last week and will take longer to finish." says Dora Luo, Water Asset Engineer, Palmerston North City Council.
The work requires a Resource Consent before it can be completed. Cleaning can't be done until the flow of the Manawatū River reaches a certain level and the water is cloudy enough so it is scheduled during the winter months when river levels are at their highest. The consent also requires this work to be carried at night.
"The swabbing process involves pushing a sponge through the pipe. The sponge, which is slightly bigger than the pipe, dislodges any sediment that has adhered to the interior surface of the walls," says Dora Luo. "We will isolate this trunk pipe to prevent the City's water quality from being affected."
However, residents, with the exception of those in the Kelvin Grove area, may find their water is discoloured during the swabbing process and up to 48 hours afterwards should any unforeseen incident occur. As precautionary measures, 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 twice a year. This is the last one scheduled for the year.
Advisory notices about the timing of the 'swabbing' will be posted on the Palmerston North City Council Facebook page and website pncc.govt.nz