E coli and drinking water quality

The following information provides advice to local government authorities and other sampling agencies about the changes to microbiological analytical techniques, reports and the suitable response requirements to take effect from 1 July 2012.

Thermotolerant Coliforms and E. coli

To date the Department of Health has always required Thermotolerant Coliform analysis for all routine drinking and recreational water quality monitoring. Recent studies have shown that not all Thermotolerant Coliforms are indicators of faecal contamination and that some are naturally present in the environment. However, E. coli (a species within the Thermotolerant Coliforms group) is present in the faeces of all warm-blooded animals. This makes it a more specific indicator of recent faecal contamination.

Indicator value and application in practice

E. coli can be used to assess:

  • source water quality and potential impacts of human and animal waste;
  • inadequate treatment;
  • post-treatment ingress of human and animal waste into distribution systems;
  • the effectiveness of risk management plans in assuring delivery of safe drinking water at consumers’ taps.
E. coli should not be present in any sample of drinking water. Risk management plans should incorporate corrective actions in the event of the detection of E. coli in drinking water. The presence of E. coli indicates faecal contamination of the water supply and the cause should always be investigated. Possible causes include inadequate treatment or ingress of contamination. Investigation will generally require further testing.

Do I need to do anything

No. From 1st July 2012, PathWest will report microbiological results using E. coli as the primary indicator with thermotolerant coliforms as an intermediate result.

Should I change my sampling frequency and method

No. There is no change to the sampling frequency, location, method, labelling, volume or any other procedure that you currently follow. (e.g. Transport time and temperature)

How will the E. coli result be reported.

PathWest will report E. coli in colony forming units/100mL of water 48 hours after processing the sample. Microbiological counts greater than zero will be reported in whole numbers while less than one ( < 1cfu/100ml) will indicate a zero count.

Will the reporting process change?

  • If the sample is negative for both Thermotolerant Coliforms and E. coli, PathWest will issue a final report 24 hours after the sample is processed.
  • If the sample is positive for Thermotolerant Coliforms, PathWest will issue an interim report 24 hours after the sample is processed but will continue testing for a further 24 hours to determine if E. coli is also present. In this case, a final report will be issued 48 hours after initial testing.

Does the reporting process change my response procedure?

No. If you are a licensed water service provider you will have been operating under the ‘confirmed E. coli’ system for some time. Your activation procedures in response to a positive thermotolerant coliform are described in your operational protocols contained within your Memoranda of Understanding that you have with the Department of Health. 

However, local government and other sampling agencies may have to consider reviewing their response systems when thermotolerant coliforms have been identified pending a confirmation of E. coli.

Will the Department of Health continue to follow up on non compliant drinking water supplies?

Yes, the Department of Health will continue to send a fax message to local government sampling agencies seeking information about the cause and response once a confirmed E. coli has been reported in a drinking water supply.

Do you need help with your Site Codes?

If you would like an up to date list of your Site Codes or a copy of the Site Code Manual please contact the Water Unit.

More information

Water Unit, Environmental Health Directorate

Department of Health

Telephone: 9388 4999

Last reviewed: 27-06-2016
Produced by

Public Health