• If the water in your tank looks, tastes or smells unusual, assume it is contaminated.
  • Water can be disinfected by bringing it to a rolling boil or by adding accurate amounts of chlorine.
  • If your tank needs cleaning, it is recommended that you contact a specialist contractor, as working in a confined space is dangerous.
  • Water that is not suitable to drink may be used to fight fires or water the garden.
If you live in a bushfire-affected area, you should be aware that your private water source could become contaminated from debris, ash, fire retardants or dead animals. Also, you should not source water from a creek that has been affected by bushfire as the water may be contaminated.

Water drawn from deep bores or wells should still be safe to use. If you suspect contamination, use an alternative water supply for drinking and food preparation. Contact your local council for a list of water carting contractors.

Preventing water tank contamination

The most effective way to prevent contamination of your water tank is to make sure it is properly sealed and to disconnect the downpipes to the tank as soon as there is a bushfire risk. Do not reconnect the downpipes until the roof has been cleaned after the bushfire, either manually or after a flush of rain.

Detecting tank water contamination

If your water looks, smells or tastes unusual, then it is likely to be contaminated. Do not use the water for drinking or food preparation, and do not give it to animals.

Water that is not suitable for drinking can still be used on the garden. Water testing is not necessary, as contamination is easily identified by a change in taste, smell or clarity.

Debris or dead animals on your roof or in the gutters should be removed. Use gloves and place in a plastic bag for disposal. Your tank water should be disinfected before re-using.

Disinfecting tank water

Water can be disinfected by bringing it to a rolling boil or by adding chlorine. For every 1,000 litres of water in the tank, you can safely add either:
  • Approximately 125 ml or 125 g of 4 per cent household bleach. Avoid using bleaches that contain detergents or other chemicals, such as perfumes
  • Approximately 40 ml or 40 g of 12.5 per cent chlorine liquid swimming pool chlorine or dairy factory chlorine
  • Approximately 8 ml or 8 g of 65 per cent granular ‘swimming pool’ chlorine.

After chlorinating, you should wait at least 24 hours before using the water to allow for harmful microorganisms to be treated.

What do I do if my roof and tank is affected by firefighting water or fire retardant? 

Firefighting activities can use any available source of water, such as farm dams and rivers. This water is not suitable for drinking, if it enters your water tank do not drink the water. 

Fire retardants have been used in Victoria for the past 30 years to slow the spread or intensity of a fire. They help firefighters on the ground and are sometimes dropped from aircraft.

If deposited on your roof, these chemicals should not enter your tank if the down pipes are disconnected. Prior to reconnecting your down pipes, hose off the roof catchment area or wait for a heavy rain to prevent possible fire retardant entering your tank. 

If fire retardants have entered enter your water tank, do not drink the water. High levels of ammonia and sulfate in water will make the water smell terrible and taste salty. It will not be suitable as drinking water for humans or animals (pets or livestock). 

Fire retardant contaminated water can still be used for irrigation and firefighting purposes.

Boiling water does not remove fire retardants or other chemicals from your water. 

If your water tank has been contaminated it is strongly recommended that you get it professionally cleaned prior to re-using it for drinking purposes. 

When to resume using your rainwater tank for drinking

If the water in your tank has not been contaminated, the water should be safe to use. However, do not reconnect your downpipes until your roof has been cleaned.
Only clean the ash and debris from your roof and gutters when it is safe to do so.

Do not use the water for drinking if it looks, smells or tastes unusual. The water and tank should be disinfected prior to use.

It should not be necessary to clean your tank after a fire unless it is grossly polluted or smells and tastes unusual as a result of aerial fire retardants.

Alternatively, you can arrange for your tank to be professionally cleaned. Where cleaning involves entering a tank, consider employing a professional tank cleaner. Tanks are confined spaces and can be dangerous to work in. Refer to your local business directory for water tank cleaners.

Where to get help


More information

Environmental health

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Environmental health basics

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Chemical and metal pollutants

Air and water quality

Food quality and safety

Bushfires, floods and extreme weather

Public health and disease control

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This page has been produced in consultation with and approved by: Department of Health and Human Services - Emergency Management

Last updated: February 2019

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