12.20pm, 2 May 2019

The water supply network at the far end of Martinborough town near Princess Street has been flushed with clean water, following the discolouration event that happened overnight.

Advice to households still experiencing brown water is to run a cold tap (preferably outside tap on your garden) until the water runs clear. This will clear the discoloured water in the pipe to your property and pull in clean water from the main pipe.

Below is some extra information about the incident, which was not included in the initial communication due to the need to get the most important information out quickly this morning.

Further explanation on what and why this discolouration event occurred

The water pipes in Martinborough have biofilm and manganese sediment in them, and when they get disturbed, dislodged biofilm and sediment can mix with the water to turn it a brown/black colour. One cause of this is air getting into the pipes. In this case, it is thought that air entered at the pumps while work was being done on them yesterday afternoon.

Because of the manganese in Martinborough water, the discolouration does occur from time to time. The last time this happened was about 4 weeks ago, during the last boil water notice. It happened in the same area, where the biofilm is at its thickest and the most manganese has settled at the bottom of the pipes.

As has been explained, “air scouring” is being used to dislodge the biofilm from the pipes and then the discoloured water will be released from the pipes by opening the hydrants. Of course, pumped, compressed air has a far greater cleaning effect than air entering at the pumps, as it did yesterday; however it is still enough to discolour the water.