We clean the pipes 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.
What to do if your water is discoloured
One of the potential side effects of cleaning the pipes is that it can cause the water to discolour for a brief period. That’s caused by the sediment in the pipes being moved.
If you find your water isn’t clear after the pipes have been cleaned, run your cold tap for 20 minutes. If the water isn’t clear in that time, then please call us on 06 356 8199 and we’ll flush the pipes near your home.
The discoloured water may stain clothes, so we advise postponing doing the laundry until the water is clear again.
Can I still use water while the pipes are being cleaned?
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.
Why can’t you give us more notice?
When we clean the pipes, we need to discharge a lot of extra water into the Manawatū River. We have a resource consent to do this, but we need the river to be in certain conditions to ensure the environmental impacts are minimal. Mainly this is about the flow of the river, and how murky it is.
We will know with 24 hours’ notice and will let you know on our website and Facebook page.
Why does the water go dirty?
Our dam has slightly higher levels of manganese. We remove almost all of it during the treatment process, but we can never get it all. Over time this can build up in the water pipes. We remove it so that you don’t have discoloured water often.
Why can’t I wash my clothes that night?
Try not to do loads of washing overnight on the night we clean the pipes. If the water does become discoloured it might stain your clothes – and we don’t want that to happen.
Will I get dirty water?
Sometimes when we clean the pipes it can cause the water to change colour briefly. We can never predict if this will happen.
If you live in Ashhurst, Bunnythorpe, Kelvin Grove or Longburn you have your own water supply so won’t be affected.
Why does our water have manganese in it?
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.
How do you clean the pipes?
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.