Managing Legionella when returning buildings into operation

Cooling tower systems

The risk of Legionella growth in cooling towers increases if the system has not been used.

It is a requirement of the Public Health and Wellbeing Regulations 2019 that cooling towers must be disinfected, cleaned and re-disinfected if the system has been shut down for greater than one month.

The department recommends that any cooling tower system that has been shut down for any amount of time should be reviewed.  The review should evaluate the critical risks following the process outlined in Section 7 Evaluating the critical risks in the document A guide to developing risk management plans for cooling tower systems

Water Delivery systems (shower systems)

There is an increased risk of Legionella growth in water delivery systems (e.g. shower systems) if they are not used, for example in communal facilities that have remained closed for an extended period. Stagnant (warm) water in unused systems may provide conditions that contribute to Legionella growth. If this has occurred, it is recommended that facilities review their water delivery systems and where required, carry out appropriate actions to manage the risks. The water system should be flushed as follows, prior to use:

  • Flush hot and cold water through all points of use (e.g., showers, sink faucets)
  • Flushing may need to occur in segments (e.g., floors, individual rooms) due to facility size and water pressure. The purpose of building flushing is to replace all stagnant water inside building piping with fresh water.
  • Flush until the hot water reaches its maximum temperature.
  • Care should be taken to minimize splashing and aerosol generation during flushing.

In general, it is recommended that showers that have been unused for 7 days or more are flushed before being used. Precautions should be taken to ensure people are not exposed to water droplets during the flushing process. Care should be taken to ensure droplets are not aerosolised. Wearing a P2/N95 mask may be appropriate in enclosed spaces where aerosol generation is likely.

More information is available in the EnHealth guidelines.

Cooling tower system management during the COVID-19 response

Circumstances related to the coronavirus (COVID-19 response),  such as changes in usual processes or reduced personnel, may mean the risk classification for cooling towers has changed.  Risk classification should be reviewed and revised as appropriate by those responsible for cooling tower safety.

Where the risk classification for the system has not changed, it is essential that cooling towers in normal operation are maintained and tested in line with the recommended operational program. 

Where the risk classification has changed, it is satisfactory to put in place a temporary operational program and this should be reflected in the risk management plan for the system.

Regulation 63 of the Public Health and Wellbeing Regulations 2019 (the Regulations) says that the maintenance and testing obligations in the Regulations do not apply to a cooling tower system that is shut down or otherwise not in use.

Legionella risk management

This section contains information about Legionella risk management for cooling tower systems and water delivery systems, as well as registration of cooling tower systems and auditing for cooling tower systems. The information is useful for:

  • cooling tower system managers and operators
  • land owners and property and facility managers
  • hospital and aged care facility engineers
  • car wash operators.

The following documents relating to legionella risk management are available to download:

Public Health and Wellbeing Regulations 2019

The Public Health and Wellbeing Regulations 2019 commenced on 14 December 2019 and have replaced the Public Health and Wellbeing Regulations 2009.

The Regulations can be accessed via the Victoria Law Today website.

Contact details

  • Legionella team

    Our phone service is available Monday to Friday, from 9.00am to 12.00pm. Postal address: GPO Box 4057, Melbourne Vic 3001