This fact sheet provides information about what to do to protect your rainwater supply before and after a bushfire.

Last updated: 09 January 2020

Preparing for the bushfire season

  • Keep roof catchment clear of overhanging branches and remove vegetation surrounding the tank.
  • Install first flush diverters, leaf stoppers on downpipes, and gutter guards to help keep roof dirt and debris out of your rainwater tank.
  • Make sure your rainwater tank is properly sealed against the entry of vermin, including rodents and mosquitoes.
  • If there is a bushfire nearby, disconnect the downpipes from your tank.

Rainwater quality after bushfires

Rainwater may be contaminated by debris, dead birds or animals, fire retardants, or large amounts of ash.

The water may also be contaminated if:

  • the tank has been burnt by fire and/or the internal lining material is damaged
  • the plumbing to or from the tank is damaged
  • the water level has increased due to water bombing.

The presence of ash and debris in rainwater is unlikely to be a health risk, but could affect the appearance and taste. Fire retardants currently used in Australia are of low toxicity, but may also affect the appearance and taste of rainwater.

Using contaminated rainwater

If you are concerned that your rainwater tastes, looks or smells unusual, or you suspect your rainwater has been contaminated, an alternative safe water supply, such as bottled water, should be used for drinking, preparing food or ice, cleaning teeth and given to animals until your tank can be cleaned and refilled.

Depending on the degree of contamination, the rainwater may be suitable for toilet flushing, garden watering, washing clothes, fire-fighting or washing down surfaces.  

In an emergency, when no other drinking water is available, rainwater can be disinfected by boiling or using household bleach (see below). This may not improve the appearance or taste of the water.

Using any rainwater contaminated with ash or other debris to fill swimming pools or in evaporative air conditioners may clog filters and pumps. Contact the air conditioner, filter or pump manufacturer for advice.

Disinfection of rainwater

Rainwater can be disinfected by bringing to a rolling boil. A kettle with an automatic shut off switch can do this. Leave the water to cool before drinking.

If you cannot boil the water, unscented household bleach (containing 4% – 5% available chlorine) may be used. Add 4 drops of bleach to 1 litre of contaminated rainwater, mix well, and allow to stand for 30 minutes before use.

You should be able to smell the chlorine faintly 30 minutes after treating the water. If you can’t, you may need to add a similar amount of bleach again. 

After a bushfire

You may find that windblown ash, debris, dead animals or fire retardants have affected your rainwater tank when returning home after a bushfire.
  • If you haven’t already done so, disconnect the down pipes from your tank. The first rainfall after the fire should be run to waste, if the roof has not been cleaned.
  • Clean your roof to remove ash and debris, if this can be done safely.
  • Check your roof and guttering for dead animals and remove if present.
  • Water testing is usually not necessary, as contamination is usually obvious.
  • If the water is contaminated the tank should be drained, cleaned and refilled. Working inside a tank can be very dangerous. Professional tank cleaners are available in some areas.
  • Filters and other water treatment equipment could be affected by debris. Refer to the manuals for your equipment or seek advice from the supplier on responding to problems.
  • After drinking water has been captured or delivered, flush taps in the property to bring through the new clean water from the tank.

Where can I get more information?

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Page Updated: Thursday 9 January 2020
Contact page owner: Environmental Health