Keeping rainwater tanks safe in bushfire-affected areas fact sheet

Information including:

• Reducing the risk of contamination from ash and smoke
• Removing contamination

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Keeping rainwater tanks safe in bushfire-affected areas 

Bushfires generate large amounts of ash and debris that can contaminate your rainwater supplies. 

Although ash and debris from burnt vegetation in rainwater does not represent a health risk, it can affect the colour, clarity and taste of rainwater.  

However, there may be other potentially more harmful contaminants, including dead animals and trace chemical residues from burnt treated timber present.

If the rainwater smells, tastes or looks unusual, assume it is contaminated and do not drink it.

Reducing the risk of contamination 

• Check your roof and guttering for dead animals. If it is safe, remove them as soon as possible to avoid contaminants getting flushed into the tank by the next rain.
• If safe and possible, remove ash and debris from the roof and gutters by thoroughly hosing off the roof catchment area if water is available, ensuring that the water does not enter the rainwater tank. 
• First flush devices or diverters are recommended as a routine installation. These operate between the roof and the tank to prevent ash and other debris from entering the tank and contaminating the water. 
• Do not collect this flush water or the first flush of rainwater after the bushfire. You may need to manually divert quite a lot of wash-down water if hosing off the roof, by fully opening the end of the device or propping the diverter to one side.
• If you do not have a first flush diverter, disconnect the inlet from the roof to the tank so the wash-down water runs to waste until the ash and debris is removed.

Removing contamination 

• If your tank inlet is not sealed, animals may enter the tank and drown. Remove dead animals from your tank (wear rubber gloves) and either: 
  • empty the tank
  • Disinfect the tank
  • Boil all water used for drinking and food preparation. 
• If you need to remove other significant contamination, drain the tank.
• You may then allow the tank to refill with rainwater or refill it with water sourced from a Council registered water carter (look under ‘Water Cartage’ in the Yellow Pages).
• Public Health Services recommends that the water used to re-fill the tank be disinfected to remove any residual contamination in the tank. For guidance on managing rainwater tanks and on disinfecting the replacement water in your tank, refer to the 2010 enHealth document Guidance on use of rainwater tanks 
• If draining and cleaning the tank is not possible in the short-term, you can use the water for purposes other than drinking, for example watering vegetation, washing and toilet flushing. 

Fire retardants and foams

• Fire retardants and foams may be present on your roof if they were used to fight the fire at your property. If fire retardant has entered your tank, do not drink the water and do not give it to pets to drink. The water can still be used for fire-fighting and irrigating your garden. If fire retardant has landed on your property or car, remove it with water by scrubbing.
• Fire retardants will often be evident by the water foaming when filling a container.