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 household 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 household water safe.

Water Collection Tanks

Tank water may be collected from:

• rain off the roof;
• natural water, e.g. streams or lakes; and
• 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, we recommend you have it tested in a laboratory.

Water contamination

Water contamination can cause illness (diarrhoea and vomiting), which can be particularly dangerous for infants, the elderly or people with damaged 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, or sewage 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 or debris entering the tank.

Safe roof collection water

Ensure your roof collection water is safe to use by following these installation and maintenance tips:

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 any old paint for lead through your public health service. Choose paint the manufacturer advises is safe for roof water collection and if possible, avoid placing television aerials etc. on the 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 your roof and spouting regularly and clean if necessary

• 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 2/3 cup) of household bleach per 1,000 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 Household Water Safety Measures

A water filter or point of use device

A water filter helps prevent contamination of your household water and can remove tastes and smells, filter out harmful bugs and remove chemicals - although most filters will only do one or two of these so it is important to get the appropriate filter for your needs.

Water filters 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.

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:

• homemade toilet flush cisterns;
• animal dosing, washing and watering systems; and
• connections for hoses used in mixing sprays, and washing down animal or bird droppings.

Disinfecting Unsafe Water

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

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

If you are concerned about your water supply, contact a Health Protection Officer at your local public health service or call us anytime on 06 857 8060 to speak to one of our Environmental Health Officers. They will recommend a local water testing laboratory. A master plumber can also advise you on all aspects of a water supply system.