What is water mains flushing and why is it done?

Flushing of Council’s water mains is done to improve water quality, by clearing potentially stagnant water and moving possible sediment deposits that have slowly built up in the pipes over time, due to internal corrosion.  

Without flushing, these deposits would increase in the pipes resulting in: 

• Decreased internal pipe size, affecting flow 

• Inability to deliver fire flows

• Additional disinfectant demand

• Chlorine degradation, low residuals

• Taste, odour and colour complaints

• Lower residual pressure

Each year Tararua Alliance staff carry out a programme of “dead end mains flushing” and “hydrant flow and pressure testing” to ensure these issues do not occur. The process is part of a routine maintenance programme that is necessary to maintain the integrity of the water system, and ensures residents receive the highest quality water possible.

The flushing includes cleaning or “scouring” the interior of water pipes by opening a hydrant and sending a rapid flow of water through them for a short period of time.

Water is sometimes discoloured after watermain cleaning, but this usually does not last long. While not harmful it is recommended that residents do not use discoloured water for any purpose that requires clean water, such as preparing foods and beverages, medical and dental procedures or doing laundry.

In the event residents draw discoloured water into the home, this can be rectified by running a cold tap for 5-10 minutes.

As a precaution, prior to using hot water it is recommended a cold tap is run for a few minutes to ensure discoloured water is not drawn into the hot water system.

Tararua Alliance will be conducting their next round of “dead end mains flushing” later this month followed by “hydrant flow and pressure testing” which will be undertaken in February.


<< Back to News(Posted on: Wednesday, 28 November 2018)