Department of Health

Key messages

  • Drinking water must not contain harmful levels of disease-causing microorganisms (bacteria, viruses or parasites) or chemicals.
  • Private drinking water supply systems consist of everything from the source water to the point of use, and should have a regular monitoring and maintenance program.
  • If you suspect that your private drinking water supply is contaminated, immediately stop using it. Do not drink from the source, or use the water for food preparation, washing or to brush teeth.

All private drinking water supply systems should be regularly monitored and maintained. Some supplies will need treatment systems to address water quality risks.

Property owners are responsible for maintaining their water supply. This requires an understanding of the supply system to address any potential hazards and risks.

Private drinking water at private properties

Home owners, landlords and estate agents have an obligation to keep their properties in good repair. This may include providing a safe water supply if there is no mains water. For more information, see Are you supplying safe water to your rental property?’

Private drinking water at commercial and community facilities

Some rural areas rely on private water for drinking and food preparation, either commercially or communally. These water supplies should comply with the Australian Drinking WaterExternal Link Guidelines.

The Guidelines for private drinking water supplies at commercial and community facilities provides guidance on using alternative water sources for these purposes.

Legislation that may be relevant includes the Food Act 1984 and the Public Health and Wellbeing Regulations 2009. Contact your local council for more information.

Private drinking water in schools

Some schools use private drinking water supplies. Schools should develop a water supply management plan to help identify hazards and address potential risks.

A guide to completing a water supply management plan – for schools using private drinking water supplies can help schools manage their private drinking water supplies.

Contaminated private drinking water supplies

If you suspect that your private drinking water supply is contaminated, immediately stop using it.

Do not:

  • drink from the source
  • use the water for food preparation, washing or to brush teeth.
  • give this water to animals to drink.

If other people use the system, notify them of the possible contamination immediately.

Check the water supply system to identify the source of contamination. For microbial contaminants, temporary treatment measures (such as chlorination or bringing water to a rolling boil) can be put in place. Chemical contaminants, however, cannot be addressed this way.


Bushfires can generate a great deal of smoke, ash and debris, which can settle on your roof. This may affect the colour, taste and smell of roof-harvested rainwater. If your drinking water tastes, looks or smells unusual, stop using it.

If your area has been affected by a bushfire:

  1. Remove ash and debris from the roof.
  2. Ensure that the first flush of rainwater is not collected in your tank.

Affected creeks may be contaminated, and should not be used as a source. Deep bores and wells should be unaffected.


If your area has been flooded, your water may be contaminated.

Floodwater can contain harmful microorganisms, debris and chemicals from overflowing sewerage systems, septic tanks and agricultural or industrial wastes.

If your water supply tastes, looks or smells unusual, stop using it.

It you suspect it may have been subjected to floodwater, such as a shallow groundwater source (like a well) or an underground tank, you should consider it contaminated.

Roof-collected rainwater, water stored in above-ground tanks and properly cased deep bores with an above-ground well-head should still be safe, provided the structure has not been damaged.

For more information see Private water sources in flood-affected areas.

Dead animals in tanks

Dead possums, birds and other animals in your tank may not necessarily cause illness, but it is best to drain all water from the tank as a precaution.

You should:

  • Wash out any sludge and animal remains from your tank.
  • Repair any holes in the roof and either scrub the inside with a household bleach solution or employ a professional tank cleaner.
  • Refill your tank with quality water and disinfect it with chlorine.

If quality water is in short supply and you cannot drain and refill the tank, remove as much of the animal carcass as possible and disinfect the water with chlorine.

If your tank needs to be cleaned, get a professional tank cleaner. Never enter a tank. Tanks are confined spaces and are very dangerous; the risks include loss of consciousness, asphyxiation and death.

For more information, see the enHealth Council’s Guidance on use of rainwater tanksExternal Link .

Cleaning tanks

If you tank needs to be cleaned, get a professional tank cleaner. Never enter a tank. Tanks are confined spaces and are very dangerous; the risks include loss of consciousness, asphyxiation and death.

For more information, see the enHealth Council’s guidance on use of rainwater tanksExternal Link , contact WorkSafe Victoria or refer to the tank cleaning section of your local business directory.


Water that is cloudy or dirty will not be suitable for drinking without treatment. It is usually more cost-effective to obtain your water from a quality source than to treat poor-quality water.

If your drinking water supply needs filtration, make sure the filter complies with the relevant Australian standards, and follow the maintenance instructions.


You should disinfect groundwater from shallow bores, and any water supply that you suspect has been contaminated by harmful microorganisms.

However, in most rural areas you do not need to disinfect rainwater from a clean roof and securely piped into a well-maintained above-ground tank, or groundwater from cased deep bores.

Disinfecting water usually involves boiling and chlorinating. Ultraviolet light systems can also be used, but these require very clear water to work effectively, and must be carefully designed, maintained and operated.


Bringing water to a rolling boil and then letting it cool to room temperature should inactivate any pathogens.

Electric kettles with an automatic shut-off are useful for this. After the water cools, store it in a clean container until it is needed.


Chlorinating your water supply is cheap and effective. Be sure to follow safety and handling instructions on all chlorine containers, especially for granular pool chlorine, and wear proper hand and eye protection when handling or preparing chlorine solutions.

Add enough chlorine so that chlorine levels are around 0.5 milligrams per litre (mg/L) 30 minutes afterwards. An initial level of 5 mg/L will usually suffice.

To work out how much chlorine to add to your tank to produce 5 mg/L:

1. Calculate the volume of water in your tank (in kilolitres):

  • For a cylindrical tank, the volume of water (in kilolitres) = D × D × H × 0.785,
    where D = diameter of the tank (in metres) and H = depth of water in the tank (in metres).
    To check your calculation, compare this volume with the maximum capacity of your tank.

2. For every kilolitre (1000 litres) of water in your tank, add either:

  • 40 mL of liquid pool chlorine (sodium hypochlorite, 12.5% available chlorine) or
  • 8 grams of granular pool chlorine (calcium hypochlorite, 65% available chlorine).

Test the residual in your water tank with a swimming pool test kit or dip strips, which are available from pool shops and suppliers.

After chlorinating, wait at least 24 hours so that the microorganisms can die. Chlorine may leave a harmless taste and odour in the water, which should disappear in around 10–14 days. Boiling the water will remove most of this taste and odour.

Potential problems


Mosquitoes often breed in water tanks. Screening inlets and overflow outlets with fine mesh is the best way to keep mosquitoes out.

If mosquitoes are already breeding in your tank, you can add a small amount of domestic kerosene or liquid paraffin. Use one of the following options:

  • 1 teaspoon of kerosene in a 1-kilolitre water tank
  • 3 teaspoons of kerosene in a 10-kilolitre water tank
  • 2 teaspoons of liquid paraffin in a 1-kilolitre water tank
  • 6 teaspoons of liquid paraffin in a 10-kilolitre water tank.

Do not use industrial or commercial kerosene. Kerosene may not be suitable for use in tanks that are constructed of, or lined with, plastic. If in doubt, check with your tank manufacturer.


Zinc from a newly galvanised tank might give an unpleasant metallic taste to the water for a while, but is not harmful.


Water pH tends to rise when the water is stored in new concrete tanks, as the concrete’s lime leaches into the water. These tanks may need to be flushed before their first use.


Your drinking water supply should not need to be tested if it is well managed and well maintained.

If you want to test your water, many analytical laboratories can provide this service. Look in a business telephone directory under ‘Analysts’. They can advise you on how to collect and submit water samples.

Laboratories can test for a range of microbial and chemical contaminants. For advice on what to test for, refer to the guidelines for private drinking water supplies at commercial and community facilities.

Reviewed 02 October 2023


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