Water quality

Compliance with the Drinking Water Standards for New Zealand

Nelson’s water supply system is assessed every year against the Drinking Water Standards for New Zealand 2005 (Revised 2008) (DWSNZ) by a Drinking Water Assessor for the Ministry of Health.

They look at two things:

  • Treatment plant: That treatment requirements have been met, and the subsequent quality of the water leaving the treatment plant meets the DWSNZ (for bacteria, protozoa, cyanotoxins and chemicals).
  • Distribution zone: That water quality monitoring requirements have been met, and the quality of the water when it arrives at your tap meets the DWSNZ (for bacteria and chemicals).

For the 2017/2018 compliance year, Nelson’s water supply system achieved full compliance against the DWSNZ for both the treatment plant and the distribution zone. 

For more information on Nelson's water planning, see the Water Supply Asset Management Plan. You can also learn about Nelson's water treatment plant.

Flush your taps

Some plumbing fittings have the potential to allow minute traces of metals to accumulate in water standing in the fittings for several hours.

Although the health risk is small, the Ministry of Health recommends that you flush a mugful of water from your drinking-water tap each morning before use to remove any metals that may have dissolved from the plumbing fittings.

We recommend this simple precaution for all households, including those on public and private water supplies. 

Changes in water clarity

There are a number of factors that can result in the water coming out of your tap looking discoloured. These include seasonal temperature changes, water mains repairs or replacement work, which can all cause this issue.  In almost all cases, this is temporary and will quickly settle down.

Here’s what to do if your water isn’t clear

The first thing to try if you are concerned about discoloured water is to run your tap for around 10 minutes. You can stop sooner if the water runs clear.

If you are still concerned after 10 minutes of running the tap please call our Customer Service Centre on 03 546 0200 and we will arrange for a contractor to flush pipes in your area.

Or you can fill out a Fix-a-gram form to report the issue here

When we are aware of problems with discoloured water in a certain area we also carry out proactive flushing of the water mains in an effort to resolve the problems as quickly as possible.

Stain removal using Oxalic Acid

If your washing has been affected by discoloured water, oxalic acid can help to remove any stains caused by the water. Read more here (92KB PDF).

Water Quality Monitoring Programme

Council has an ongoing water quality monitoring programme to ensure the safety and quality of drinking-water throughout the network that involves the following:

  • 10 sample points in the reticulation are tested for chlorine, turbidity, pH and temperature every week. Five of these have a bacteriological sample taken (for E.coli and total coliforms).
  • 15 sample points at tanks and reservoirs are tested for chlorine, turbidity, pH and temperature every week. Five of these have a bacteriological sample taken (for E.coli and total coliforms).
  • Anytime a watermain is shutdown for a repair or new connection, a sample is taken for chlorine, turbidity, pH, temperature and bacteria (E.coli and total coliforms).