Rainwater tank contamination
Water in rainwater tanks on your property can be contaminated during or after a fire or flood, by ash, smoke, debris, bacteria, fire or firefighting activities.
If there is any risk of contamination, do not use water from your rainwater tank for the following activities:
- drinking
- preparing foods
- making ice
- washing and bathing
- cleaning teeth
- watering animals.
How to tell if your rainwater tank is contaminated
Fire contamination
- Your roof is covered by ash or other fire debris
- There are dead animals on your roof or gutters or in your tank
- You think that your roof was covered by fire suppressant water either dropped by aircraft or sprayed from ground units
- The tank has been burnt by fire and the internal lining material is damaged
- The plumbing to or from the tank is damaged
- The water is cloudy, tastes or smells unusual or has an unusual colour
- The water contains debris or ash
- The water level has increased.
Flood contamination
- You think the tank roof was covered by floodwater
- There are dead animals on your roof, gutters, or in your tank
- The plumbing to or from the tank is damaged
- The water is cloudy, tastes or smells unusual, or has an unusual colour
- The water contains debris or mosquitoes.
Using contaminated water
If you think that your water tank has been contaminated in any way, you can still use the water to:
- flush toilets
- water the garden
- wash clothes (providing it will not stain clothes)
- wash cars
- fight fires.
Do not use rainwater contaminated with debris to fill swimming pools or evaporative air conditioners because the debris in the water may clog filters and pumps. Contact the air conditioner, filter or pump manufacturer for advice.
Do not use contaminated water for drinking, cooking, washing your face or cleaning skin wounds.
Non-potable water
Water that may not be safe to drink may be okay for showering, bathing and personal hygiene. It is important to have clean and safe water source personal hygiene.
Tips to keep yourself healthy
- Keep hands clean to help prevent the spread of germs. Wash hands with soap or sanitiser, and water that has been boiled or disinfected.
- Ensure your non-drinking water source is safe for bathing and showering. Be careful not to swallow any water or get it in your eyes or up your nose. If you are unsure that your non-drinking water is safe to use for washing yourself, check with local government or the Department of Health.
- Only use drinking water to brush your teeth.
- Only use drinking water and soap to wash open wounds. Cover with a waterproof bandage and if a wound becomes red, swollen or oozes, get immediate medical care.
- Do not bathe in water that may be contaminated with sewage or toxic chemicals, or in rivers, streams, or lakes that are contaminated by floodwater, sewage, or animal waste.
- For contact lens hygiene (use and storage) follow the guidance on Acanthamoeba and contact lens use.
- For nasal irrigation hygiene, follow the guidance on Nasal irrigation - is it safe?
After fire
Other sources of water
Water drawn from deep bores or wells should be safe to use. Do not obtain water from a creek or stream that has been affected by bushfire as the water may be contaminated.
First rains after a fire
Ensure that all rainwater from the first good rainfall event after the fire is run to waste, as this may be contaminated by ash and other pollutants from the fire.
Can I treat rainwater to a drinking water standard if it has been contaminated by fire?
No, it is usually very difficult and expensive to remove effectively any contamination caused by fire suppressants or any other potentially harmful by-products caused by ash from burnt bush, plastics and metals.
After flood
Electrical safety
If you think your tank's pump or electrical equipment has been impacted by floodwater, you need to have it inspected and declared fit for use by a licensed electrician before reusing pumps or maintaining the tank.
Bore water for drinking
Floodwater may contaminate a drinking water bore system or water storage tank.
If floodwater is suspected to enter the bore casing, the bore water is likely to be contaminated. Do not drink or use this water for cooking, washing your face or cleaning skin wounds.
If you are not sure if the bore has been inundated with floodwater, it is recommended the water is tested to confirm it is safe.
Drink and cook with bottled water.
Drinking water drawn from deep bores where flood waters have not entered the bore casing may be safe to use, though may safest to check.
Following flooding, disinfect the water from the bore pump to the storage tank by following the Emergency treatment of drinking water supplies. Seek specialist advice if required.
If your drinking water tank is supplied by a bore, the same steps to remediate the tank should be followed as those listed for rainwater tanks above.
Bore water – garden purposes
After flooding, do not use garden bore water for drinking, cooking, washing your face or cleaning skin wounds.
You may use bore water to wash clothes or for irrigation.
Emptying, cleaning and sanitising a rainwater tank
- If you have an underground tank, do not empty the tank while the ground is still flooded as it may damage the tank walls and plumbing.
- Once the tank has been emptied, the inside of the tank should be hosed out with clean water to remove soil and debris.
- Cleaning large tanks can be a safety risk. Seek advice from a qualified professional tank cleaner to clean inside your tank.
- Following cleaning, sanitise the tank. Ask your tank supplier for the best sanitation method based on the material the tank is made of.
- Any plumbing, guttering, downpipes and roof surfaces connected to a tank that has been flooded will also need to be cleaned and sanitised.
Refilling your rainwater tank
You may need to drain and refill your tank with water from a commercial water carting company. Before you do, make sure that:
- the tank or any associated pipework has not been damaged
- the tank has been de-sludged and cleaned, if contaminated, by a specialist contractor.
Do not reconnect your down pipes until your roof and gutters have been cleaned or rainwater from the first rains after the fire has been run to waste.
Make sure that the commercial carting company:
- uses the tanker exclusively for drinking water
- gets the water from a scheme drinking water supply
- has treated the water with at least 1 milligram per litre of chlorine while in transit
- follows the Department’s water carting guidelines (external site).
Water testing
If you would like to test the chemical quality of water in your water tank, contact a National Association of Testing Authorities (NATA) (external site) accredited chemical laboratory.
Refer to the Department of Health Publication, Standard Drinking Water Test (external site) for further information.
If you need advice about interpreting the results from any water testing, contact the Water Unit at the Department of Health by emailing ehinfo@health.wa.gov.au or phoning 9222 2000.
Last reviewed: 13-10-2023
This publication is provided for education and information purposes only. It is not a substitute for professional advice. Information about a service, product or treatment does not imply endorsement and is not intended to replace professional advice. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified professional for answers to their questions.