Chlorinated drinking water

Safe drinking water supplies are critical to our health and wellbeing. Water from untreated sources such as streams, bores, dams and rainwater tanks can sometimes contain harmful micro-organisms that cause serious illness or, in some cases, death.

Chlorine has been used around the world for more than 100 years to disinfect drinking water supplies. As a result many water-borne diseases such as cholera, dysentery and typhoid have been effectively controlled.

Why is chlorine used?

Chlorination of drinking water is a proven public health measure with an excellent track record of safety and effectiveness.

Chlorine is a safe way to protect drinking water supplies from contamination against harmful micro-organisms.

In addition to being safe to use, chlorine is:

  • simple to use
  • reliable
  • effective
  • inexpensive.
As it has been used for so many years worldwide, the methods and equipment needed to chlorinate water are well designed and effective. 

Another important benefit of using chlorine in drinking water is that once the water is treated, a small amount of chlorine remains in the water distribution system.

This remaining chlorine provides continued protection from bacteria and other organic contamination while the water is delivered to your tap.

What else is chlorine used for?

Chlorine is one of the most widely used disinfectants found in homes, industry and health care facilities.

Chlorine based products are also used to sterilise baby feeding bottles, to disinfect swimming pools, spas and hydrotherapy pools and to disinfect equipment in food premises. It is also used in a wide variety of sanitation, water and wastewater treatment processes, both as a disinfectant and as an oxidant.

Is chlorine effective against all micro-organisms?

When used in drinking water, chlorine is effective against micro-organisms that are likely to pose a threat to your health if consumed, including bacteria such as Escherichia coli, Listeria, and Salmonella and amoeba such as Naegleria species.

How much chlorine is in our drinking water?

Normal chlorine concentrations in scheme drinking water supplies in Western Australia usually range from 0.5 to 1.5 milligrams per litre.

Chlorine levels may vary due to the flow rate of the water in the system, your proximity to the water treatment plant and during maintenance periods.

Most people will be able to smell chlorine in drinking water from about 0.6 milligrams per litre, but some people are particularly sensitive and can detect amounts as low as 0.2 milligrams per litre.

The Australian Drinking Water Guidelines (external site) requires that the level of chlorine in drinking water should not exceed 5 milligrams per litre (5 parts per million).

For more information on the chlorine level in your drinking water supply, please contact your local water supplier.

What if I can taste or smell chlorine in my water?

Drinking water providers in Western Australia supply water that is chlorinated to a level that maintains an effective disinfectant residual.

This means that drinking water supplies in Western Australia can sometimes taste or smell of chlorine, particularly if the water is warm.

The chlorine smell will evaporate simply by leaving a jug of uncovered water in the fridge for a short period of time. Alternatively you can use a simple jug filter fitted with an activated carbon filter cartridge, or just pour water from one jug to another several times.

Does chlorine cause any negative health effects?

No. Negative (adverse) health effects have not been seen in people drinking water chlorinated.

Long term animal toxicity studies have revealed no carcinogenic (dangerous) effect from drinking chlorinated water. More detail about this aspect can be found in the Australian Drinking Water Guidelines (external site).

Does chlorine produce by-products in drinking water?

When water containing organic matter is treated with chlorine it is possible that small amounts of chemical by-products known as trihalomethanes can be formed.

Many scientific investigations have been conducted around the world over the past 40 years to determine if a health risk exists. To date no conclusive evidence has been found.

Even so, as a precaution, the Australian Drinking Water Guidelines (external site) limit the total amount of trihalomethanes in drinking water to no more than 0.25 milligrams per litre.

What is chloramination and can it affect fish?

Chloramination is a disinfection process that involves the addition of ammonia as well as chlorine. These two chemicals react to form chloramines, which are effective disinfectants which persist in the water supply system for longer periods.

This is a major advantage in maintaining the high microbiological quality of water supplies that travel over long distances.

However, it can lead to problems for owners of fish ponds and aquariums because chloramines, like chlorine, are toxic to fish. Free ammonia, which may be present in chloraminated water, is also toxic to fish.

In Western Australia water supplied to the Goldfields and Agricultural Supply Scheme is chloraminated from Mundaring Reservoir, where the water travels over long distances to a number of regional wheat belt communities. To find out if this water is supplied to your property please call the Water Corporation on 13 13 75.

For advice on how to make water safe for fish, please refer to the Water Corporation (external site) or seek advice from your aquarium or fish supply shop.

Who makes sure that your scheme drinking water is safe?

The Department of Health continually monitors the microbiological and chemical quality of drinking water supplied by all licensed scheme drinking water providers to ensure that it is safe to consume.

Drinking water providers in Western Australia are also required to monitor and report the residual level of both chlorine and trihalomethanes in drinking water and to publish annual reports that provide detailed information about the quality of drinking water supplied to consumers.

If you are concerned about the quality or safety of your drinking water please contact us or your local drinking water provider.

Should I treat my water?

There is no need for householders to further chlorinate drinking water that is supplied by a licensed drinking water supplier.

However, if you obtain your drinking water from a rainwater tank, bore or other private water source, or if you store drinking water in large tanks on your property, it is possible that it could be contaminated with harmful bacteria and may need to be disinfected before use.

The Department of Health recommends that any water that is not provided by a licensed drinking water service provider be professionally tested and treated before it is used for domestic purposes such as drinking, bathing or cooking.

How can I get my water tested?

Water testing can be done by any accredited National Association of Testing Authorities (NATA) (external site) laboratory.  The Department of Health has arranged with a number of Western Australian NATA accredited laboratories a uniform testing process called a standard drinking water test that will test for microbiological and chemical contaminants of most interest.

Remember

  • Chlorination of drinking water is a proven public health measure with an excellent track record of safety and effectiveness.
  • Chlorinated drinking water is safe to drink.
  • You can reduce chlorine smell or odour by placing a jug of water in the fridge uncovered.
  • It is not necessary to treat scheme drinking water as it is continually monitored by the Department of Health.
  • Bore, rain water tank and other water sources should be professionally tested and treated before the water is used for drinking or food preparation.

More information

Water Unit, Environmental Health Directorate

Department of Health

Telephone: 9388 4999

Last reviewed: 27-06-2016
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Public Health