Update on discoloured water in Morrinsville

We have resolved the issue at the Water Treatment Plant that was causing dirty water, and finished flushing the pipes. People may still see some discolouration as the water works its way through the pipes to their houses, but we expect to see this clear by the end of today (Friday 17 November).

The water discolouration was caused by an increase in manganese and iron compared to normal. The increased level of manganese can cause staining to laundry or porcelain e.g. your bath tub and toilets.

Stain removal using Oxalic Acid

A solution of oxalic acid can help remove iron and manganese stains from clothing. It is available from businesses such as Bunnings or Mitre 10, generally in 500g packs, at a cost of around $18.

If the recent discoloured water has stained your washing, you should:

  • Ensure that your water supply is clear prior to using oxalic acid
  • Keep stained washing wet/damp
  • Add 75g of oxalic acid per litre of warm, clear water
  • This should be done in a large plastic bucket (NOT metal)
  • The stained clothing should be soaked in this solution for approximately five minutes
  • If a large quantity is stained it may be better to soak several smaller loads in succession so the solution is brought into contact with all parts of the affected clothing
  • Once the stains have been dissolved the clothing should be rinsed thoroughly in clear, cold water. The washing solution can be discarded by flushing down an outside drain

NOTE: Oxalic acid cannot be used as a measure to prevent the washing from being stained and therefore should never be added to the washing machine.


  • Correct usage and handling of this product should not result in any problems or health issues. While the acid is not corrosive like other acids, it is poisonous if swallowed. Consequently, should any spillage or splashing occur, ensure that it is wiped up immediately.
  • The oxalic acid must be kept out of reach of children. As an extra precaution, children should be kept out of the laundry while the cleaning operation is carried out. In the event of poisoning or suspected poisoning, immediately implement the first aid treatment outlined on the packaging.
  • Any Material Safety Data Sheet that may be provided by suppliers should be read and understood.