Bushfires and rainwater quality

Bushfires generate large amounts of ash and debris which have the potential to contaminated rainwater supplies. Although the presence of ash and debris in rainwater does not represent a health risk, it could affect colour, turbidity and taste.

There are some simple steps that can be taken to ensure that your rainwater supply is suitable for drinking after a bushfire.

Reducing the possibility of contamination

  • Where possible, remove any ash and debris deposited on the roof and gutters by brushing or washing. If washing disconnect the inlet to the tank. Care should be taken to avoid accidents through slips and falls.
  • Check the roof and guttering for dead animals and remove if present.
  • Do not collect the first flush of rainwater after the bushfire. Use a first flush diverter between the roof and the tank to prevent ash and other debris from entering the tank and contaminating the water. First flush diverters can be purchased from most hardware stores and rainwater tank suppliers.
  • In the absence of a first flush diverter, disconnect the inlet from the roof to the tank until ash and debris has been removed.

Detecting contamination

  • If ash and debris has been washed into the tank in sufficient quantities by rain occurring before an opportunity to divert the first flush or roof-hosing as part of a fire plan, the quality of the water may be affected.
  • If the rainwater smells, tastes or looks unusual, assume it has been contaminated.

Fire retardants

  • Fire retardants and foams may be deposited on roofs. This material can be washed into tanks when water is hosed on to the roof as part of fire protecting activities, or when it rains after a bushfire.
  • The recommended concentrations of the commonly used retardants and foams should not present a risk to health, but they may affect the taste of the water if washed into the tank. Fire retardants also contain detergents that may cause the water in the tank to froth.

Removing contamination

  • Drain and clean the tank and allow it to refill with clean rainwater or fill with water purchased from a water carter (look under ‘Water Cartage’ in the Yellow Pages® and check for registration with SA Health).
  • Alternatively the water can be used for purposes other than drinking or food preparation such as garden watering.
  • If a dead animal is found, empty and clean the tank. If this process has to be delayed, remove the animal remains and disinfect tank water with chlorine.

Further information

For further information on rainwater tanks and bushfires: