Emergency treatment of drinking water supplies

If disaster strikes, it is possible that the normal supply of water will be affected.

When the safety of the normal water supply cannot be guaranteed, the Department of Health or your water supplier may issue advice to boil or treat it with chemicals prior to use.

Your local government and/or local or district emergency management committee are usually the best people to advise you on the availability of emergency drinking water and other essential services.

This information is normally given out:

• on the radio
• on television
• on emergency management websites
• via printed material.

Extreme caution should be exercised before drinking water from bores, wells and dams. It is likely that contamination may have occurred, especially during times of flooding.

If unsure, disinfect all water to be used for drinking, food preparation, cooking, baby food and for brushing teeth.

Short-term actions

Where clean drinking water is not immediately available it is possible to obtain limited amounts of safe drinking water by:

• draining your hot water tank
• melting ice cubes you have in the freezer.

You can disinfect small quantities of water in 2 ways:

• boiling (the simplest and best)
• chemical treatment.

Boiling water

Vigorous boiling for at least 1 minute will kill any disease-causing micro-organism present in the water.

The flat taste of boiled water can be improved by pouring it back and forth from one clean container to another.

Alternatively, allow it to stand for a few hours with a loose fitting cover.

Chemical treatment

When boiling is not practical, chemical disinfection can be used.

The simplest, most effective chemicals are chlorine and iodine.

Chlorine is generally more effective than iodine.

However, while they are both effective against most micro-organisms, including giardia, they may not be effective against cryptosporidium.

Chlorine disinfection

Water may be disinfected using household bleach containing chlorine (but not containing added perfumes or detergents).

Look for the percentage of available chlorine on the label and use the information in the following table as a guide to disinfect the water.

The treated water should be mixed thoroughly and allowed to stand for 30 minutes.

The water should have a slight chlorine odour. If not, repeat the dosage and allow the water to stand for an additional 15 minutes.

The chlorine taste can be objectionable in treated water.

The taste can be made more pleasant by allowing the water to be exposed to the air for a few hours.

Alternatively, pour it several times from one clean container to another.

Granular calcium hypochlorite

Another option is to use swimming pool grade granular calcium hypochlorite.

Add, and completely dissolve, 1 heaped teaspoon of calcium hypochlorite in 7.5 litres of water.

This mixture will produce a concentrated chlorine solution of approximately 500 mg/L (milligrams per litre).

The concentrated chlorine solution can then be used to disinfect water in the ratio 1 part concentrated chlorine to 100 parts of water.

If using swimming pool grade granular calcium hypochlorite, always follow the instructions on the container in relation to safe handling and disposal of the product.

Chlorine tablets

Chlorine tablets containing the necessary dosage for drinking water disinfection can be purchased from pharmacies and sporting goods stores.

The tablets should be used in accordance with the manufacturer’s instructions.

Tincture of iodine

Common household iodine from a first aid kit may be used to disinfect water.

Add 5 drops of 2 per cent tincture of iodine to 1 litre of clear water.

If the water is cloudy add 10 drops of the tincture.

Let the solution stand for at least 30 minutes before drinking.

Iodine tablets

Commercially prepared iodine tablets containing the necessary dosage to treat drinking water can be purchased at a pharmacy or sporting goods store.

Iodine tables should be used in accordance with the manufacturer’s instructions.

Iodine is only suitable for short-term emergency use.

It should not be used repetitively or for longer than 1 week in any single emergency situation.

Containers for treated water should, if possible:

• be clean
• have covers
• be stored above ground
• be in a cool place
• be cleaned periodically
• be mosquito proof.

Swimming pool chlorine can be used to treat large quantities of water in containers, such as rainwater tanks and vehicle mounted water tanks.

The initial dose of chlorine required to treat any potential contamination is:

• 14 grams (1 level teaspoon and 1 level dessertspoon) of calcium hypochlorite (60 to 70 per cent) per 2000 litres

or

• 40 millilitres (8 teaspoons) of sodium hypochlorite (12 per cent) per 1000 litres.

The water should be stirred then left to stand for at least 24 hours to allow the chlorine taste and smell to dissipate.

To maintain a safe water supply after the initial dosage, each week add:

• 5 grams (1 level teaspoon) of calcium hypochlorite (60 to 70 per cent) per 5000 litres

or

• 8 millilitres (1 dessertspoon) of liquid sodium hypochlorite (12.5 per cent) per 2000 litres

Allow the water to stand for a minimum of 2 hours before drinking.

Note

• Do not pour water onto chlorine.
• Always add chlorine to water.
• Always mix chlorine in the open air.
• Always follow the instructions on the pool chlorine container in relation to safe handling and disposal of the product.