Private water supply testing

This page has information on the testing process and interpretation of microbiological analysis of drinking water.

If you are providing or using drinking water not sourced from a reticulated licensed water supply, you should get your water tested regularly. 

This applies if the water comes from a bore, rainwater tank or surface water source.

For more information on testing private water supplies get the following fact sheets:

Contact Environmental Health if you have concerns about lead, uranium, arsenic or cadmium in drinking water.

Why you should test drinking water

Drinking water should be regularly tested to ensure that it is free of harmful bacteria and is safe for drinking.

Disinfection has the greatest impact on the presence of microorganisms in drinking water.

The Australian Drinking Water Guidelines 2011 (ADWG) state the greatest risk health from drinking water is pathogenic microorganisms. 

Pathogenic microorganisms may be in the water as a result of human or animal faecal contamination. 

Drinking water samples are tested for indicator bacteria called E. coli. 

This microorganism is found in very high numbers in the intestines of animals and humans, which makes it a good indicator of recent faecal contamination in drinking water. 

Who can test drinking water

Water can be tested for microbiological contamination by any accredited laboratory. 

You can get analytical services from the Northern Territory Government Water Microbiology Laboratories at Berrimah and Alice Springs. Contact details are below.

They can arrange for the supply of sterile prepared sample bottles, advise on how to collect a water sample and on the best delivery method and time. 

You will need to pay for water sample testing. For analytical services contact:

  • Alice Springs - Arid Zone Research Institute (08) 8951 8110
  • or Darwin - Berrimah Farm (08) 8999 2347.

Reading a microbiological analysis of water

Most microbiological analyses for drinking water will provide the numbers of total viable bacteria, total coliforms and E. coli present in 100ml of water.

Total viable bacteria have no direct relation to faecal contamination and are not a health risk however, they indicate the general content of the water.

Total coliforms refer to a large group of bacteria that can be of faecal or non-faecal origin. 

Many of the non-faecal organisms grow naturally in the environment, including water. 

Total coliforms do not present a direct health risk, but can provide information on the efficiency of drinking water disinfection. The ADWG does not set a guideline value for total coliforms.

E. coli present in drinking water means that human or animal faeces have contaminated the water. 

Faeces can harbour a number of other pathogenic or disease causing organisms. 

The guidelines state that to make sure drinking water is safe to drink, no E. coli should be detected in any 100ml water sample.

Drinking water contaminated with E. coli

If your drinking water sample is positive for E. coli it is recommended that water used for drinking and brushing your teeth is boiled and cooled before use, or that bottled water is used for that purpose, until repeat sampling shows your drinking water is E. coli free.

There are a number of treatment processes that remove E. coli and other pathogenic microorganisms from a drinking water supply, including filtration, UV and chlorine disinfection. 

For more information on making water safe and drinkable, including the disinfection of water tanks with chlorine, read about rainwater tanks.

Contact Environmental Health for more information.

Last updated: 25 July 2017