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Safe Household WaterWai pai mō te kāinga

Safe water is vital for good health.

Water used for drinking, teeth cleaning, hand washing, bathing, showering, food preparation and cooking needs to be free from harmful germs and chemicals. So does drinking water for stock and pets.

Water for washing clothes, toilet flushing and general cleaning should be clear to prevent staining.

If your water comes from a mains supply, your water safety is monitored by your local authority. If your water comes from a water collection tank, it is up to you to keep your water safe.

Water Collection Tanks

Tank water may be collected from:

  • Rain off the roof
  • Natural water e.g. streams or lakes
  • A bore (deep hole in the ground)

Water supplies from all of these sources can become unsafe. For example:

  • Roof water may be corrosive, or may become contaminated from agricultural spraying or bird or possum droppings.
  • River or stream water and shallow bore water may contain harmful germs or chemicals or be discoloured and unpleasant to taste.
  • Bore water can become hard and corrosive.

If you are unsure about the quality of your water, have it tested in a laboratory.

Water Contamination

Water contamination can cause illness (diarrhoea and vomiting) which can be particularly dangerous for infants, very old people or people with damage immune systems.

Contaminants of a collection tank water supply may be caused by:

  • Animal or human faeces entering at the source of the supply. These can carry harmful germs such as Cryptosporidium, Giardia, Campylobacter and E-coli 0157 which can cause serious illness.
  • Bird, possum or other animal droppings on the roof.Sewage etc being flushed the wrong way through the supply system.
  • Chemicals e.g., agrichemical spray drift.
  • Lead flashing on the roof causing high lead levels in collected water.
  • Leaves, volcanic ash, etc entering the tank.

Ways To Keep Your Roof Collection Water Safe

Install the entire system correctly

  • Include a first flush diverter (a device that prevents the first water collected from carrying any debris into the collection tank). Place the pipe directly from your roof if you have an older tank.
  • Use plastic pipes.
  • Use safe roof paint. Check the old paint for lead through your public health service. Choose paint the manufacturer advises is safe for roof water.If possible avoid placing the TV aerial etc on roof for birds to perch on.
  • Avoid planting trees close to the house.

Cover the tank to prevent animals, birds and other matter from entering.

Check the cleanliness of your roof and spouting regularly and if they need cleaning

  • Disconnect the pipe that feeds water to the tank.
  • Use clean water to scrub the roof and spouting to clean off all dirt, animal droppings and paint flakes.
  • Thoroughly flush clean water through the spouting to remove any dirt left from cleaning the roof.
  • Reconnect the pipe that feeds water to the tank.

Clean and disinfect your tank after dry spells or if dirty

Most tanks need cleaning every six to twelve months. Flush the tank out with water using a broom to push sludge out through the scour valve. After cleaning, disinfect the tank using about 167 ml (about 2/3rds of a cup) of household bleach per 1000 litres of water.

Run the mixture through all your household water pipes and taps until it is gone. Then refill the cleaned tank with water for household use.

If you have a water filter (point of use device) it needs regular maintenance too.

Other Ways To Keep Household Water Safe

A water filter or point of use device

A water filter helps prevent contamination of your household water. It can be used to treat all household water and placed where all water entering the house passes through it, or can be used for just one tap. It should be placed where you can get at it for cleaning.

A water filter can:

  • Remove tastes and smells
  • Filter out harmful bugs
  • Remove chemicals

Note: Most filters will only do one or two of these. It is important to get the appropriate filter for your needs.

Water Pipes

Untreated water and water from mixed sources, is often corrosive so plastic pipes should be used to carry cold water.

A backflow prevention device stops contaminated water from flowing back into the home supply. It is needed on:

  • Home made toilet flush cisterns
  • Animal dosing, washing and watering systems
  • Connections for hoses used in mixing sprays, washing down animal or bird droppings.

Disinfecting Unsafe Water

If you are unsure about the safety of your drinking water supply, you can disinfect some by:

  • Using an approved filter or purifier
  • Boiling the water for one minute
  • Adding chlorine. Half a teaspoon of household bleach added to 10 litres of water kills most germs, but only boiling kills Cryptosporidium.

If you are concerned about your water supply contact a Health Protection Officer at your local public health service or an Environmental Health Officer at your local Council. They will recommend a local water testing laboratory. Remember, a master plumber can advise on all aspects of a water supply system.

Information supplied by Ministry of Health and Health Funding Authority.


For more information please contact the Wairoa District Council.

+64 6 838 7309
97-103 Queen Street, Wairoa 4108
PO Box 54, Wairoa 4160


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