Water tanks on your property

Regular maintenance of the whole system, from roof to tank to tap, is the key to good water quality for your home.

• Keep roof catchments, including the gutters and down pipes, clean and clear of leaves.
• Remove overhanging branches of trees, shrubs and potential perches for birds such as wires and TV antennas.
• Cover the inlet and overflow of your tank with a mesh to prevent birds, animals and insects from gaining direct access to the water.
• Make sure your tank has a cover to prevent light from reaching the water, as light encourages the growth of bacteria and algae. The cover should have a tightly sealed hatch, to allow access to the tank for cleaning and inspection purposes.
• Each year allow the first good rains to rinse the roof and gutters and run to waste, by using a first flush diversion device. Using a first flush diversion device will prevent the first portion of roof runoff, which is likely to collect contamination, from entering the tank.
• Ensure that guttering and pipework is self-draining, or fitted with drainage points to prevent corrosion and contamination by metal.
• Maintain your leaf trap, as this will reduce the amount of leaves and debris that enters the rainwater tank through the inlet.

Rainwater can be collected from most types of roofs including:

• cement
• terracotta tiles
• Colorbond®
• galvanised iron
• Zincalume®
• polycarbonate
• fibreglass sheeting
• slate.

It is safe to collect rainwater from asbestos or fibro cement roofs. There is no evidence to suggest that asbestos related diseases occur from drinking this rainwater.

Do NOT collect rainwater from a roof that is:

• made from preservative treated wood (copper chrome, creosote or pentachlorophenol)
• coated with bituminous products
• coated with lead based paints (including any gutters).

Do NOT collect rainwater from parts of the roof with:

• a chimney from a wood burner
• discharge pipes from roof-mounted appliances such as evaporative air conditioners or hot water systems
• chemically treated timbers
• lead-based paints or flashings.

Speak to your water tank supplier about identifying materials on your roof that could contaminate your rainwater.

Rainwater supply

The amount of water required to adequately supply your needs is dependent upon:

• rainfall
• roof area
• rainwater tank size
• the amount of water used in and around your house.

The Perth Residential Water Use Study (external site) and other publications of the Department of Water (external site) provide useful information about the average in-house water use for appliances based on the number of occupants.

Data about rainfall is available from the Bureau of Meteorology (external site).

A reticulated scheme drinking water supply (scheme water) is the safest and most reliable source of drinking water in urban areas in Western Australia.

Rainwater from your roof can contribute to your yearly water needs and help conserve drinking water reserves, when you use rainwater for activities such as:

• watering your garden
• flushing your toilet
• washing your clothes
• washing your car.

If you live in an urban area and you would like to drink rainwater, you should be aware that there might be an increased risk of pollution.

It is also important to protect our reticulated scheme drinking water supply from any risk of contamination through backflow from private water tanks.

To protect the scheme water supply, water tanks that are connected to scheme water must be fitted with an approved backflow prevention device installed by a licensed plumber.

You may need to top up your tank with water from a commercial water carting company. Before you do, consider these points:

• Is the tanker exclusively used for drinking water?
• Has the water come from a scheme drinking water supply?
• Has the water been treated with at least 1 milligrams per litre of chlorine whilst in transit?
• Does the water carting company follow the Department’s water carting guidelines (external site)?

The answer to each of these questions should be “Yes”. If the answer to any question is “No”, or you are not sure, and you choose to top up, then the water in the tank should be regarded as non-potable (i.e. not suitable for drinking or food preparation).

Can you fill your rainwater tank with bore water?

Yes, depending on what the water in the water tank is to be used for.

Depending on local characteristics, bore water may be suitable for uses including stock watering, irrigation, flushing toilets and washing clothes or cars.

Bore water should not be used for drinking, bathing, watering edible plants, food preparation or cooking unless it has been properly tested and treated to make it suitable for the intended use.

For more information about bore water, see our Bore water page.

Solar hot water systems contain heat transfer fluids, corrosion inhibitors (substance that stops the chemical reaction that creates corrosion) and anti-scaling chemicals that can contaminate water in your water tank if they spill or leak.

Do not collect rainwater from parts of the roof with discharge pipes from roof-mounted appliances such as evaporative air conditioners or hot water systems.

When carrying out maintenance on roof-mounted hot water systems, be sure that maintenance personnel:

• follow correct procedures to prevent rainwater contamination for any work conducted on the roof
• disconnect the pipe to the rainwater tank, and only reconnect the pipe once you are certain there is no leakage after maintenance
• contain and dispose of appropriately all heat transfer fluids, corrosion inhibitors and anti-scaling chemicals from solar hot water systems.

Regular disinfection of water in your water tank should not be necessary.

However, if your water is likely to be contaminated you can disinfect it with swimming pool chlorine, in accordance with the table and notes below.

Notes

• Use either granular calcium hypochlorite or liquid sodium hypochlorite. Do not use both at the same time.
• Calculate the amounts of chemical to add based on the volume of water in your tank at the time, not the total capacity of your tank.
• Do not use stabilised chlorine (cyanurate).
• Allow a minimum of 2 hours before drinking.
• Mix the chlorine in a plastic bucket in the open air before adding it to the tank.
• Do not pour water onto chlorine. Always add chlorine to water.
• Always follow the instructions on pool chlorine containers in relation to safe handling and disposal of the product.

Do I need to clean my tank?

Inspect your tank every 2 to 3 years for the accumulation of sediment (sludge) on the tank floor.

The easiest way to remove sludge is by opening the sludge or scour valve located at the bottom of the tank.

Remember that the inside of a tank is a confined space with little ventilation. If you need to clean your tank consider using a professional tank cleaning service.

Do I need to test my tank?

Routine testing of water in your domestic water tank is not normal practice and in most cases would not be necessary.

If tested, your results should be compared with the guideline values contained in the Australian Drinking Water Guidelines (external site).

Refer to the Department of Health Publication, Standard Drinking Water Assay (external site) for further information.

See also the National Association of Testing Authorities (NATA) (external site) for a current list of registered analytical laboratories.

Water tanks can become breeding sites for mosquitoes that can cause severe nuisance and carry serious diseases.

In Western Australia, the mosquito most commonly found to breed in water tanks is a proven carrier of Ross River and other mosquito borne viruses.

To prevent mosquitoes from breeding, make sure that:

• Guttering and pipework is self-draining, or fitted with drainage points.
• Water is not allowed to pool under the overflow outlet or tap as these can become mosquito breeding sites.
• All water tanks are completely sealed. Any holes and spaces will allow mosquitoes to enter your tank.
• The inlet and inspection ports have a fine mesh cover to stop mosquitoes and other insects getting into your tank.
• The overflow is also covered with an insect proof cover, such as plastic insect mesh wired around the pipe.
• Insect mesh is no coarser than 12 x 12 meshes per 25 square millimetres.

A useful short term solution to stop mosquito breeding is to add 1½ cups of liquid food grade paraffin oil (in large tanks greater than 10,000 litres) to the water.

When using food grade paraffin oil:

• add a sufficient amount of food grade paraffin oil to produce a thin film over the water surface
• add the food grade paraffin oil at the end of the winter rains
• add more food grade paraffin oil if the tank overflows
• check the tank several times a year as both food grade paraffin oil and water will evaporate over time.