Legislation and guidelines for cooling towers and water systems

Building owners and operators must ensure the correct design, installation, operation and maintenance of air-handling, water systems and cooling towers installed in Western Australian buildings to protect the public from outbreaks of Legionnaires’ Disease and other airborne diseases originating from air-handling and water systems in WA


Air-handling and water systems are managed under the Health (Air handling and Water Systems) Regulation 1994 (Regulations).

The overall objectives of the Regulations are to:

  • Ensure the correct design, installation, operation and maintenance of air-handling and water systems and cooling towers installed in Western Australian buildings.
  • Protect the public from outbreaks of Legionnaires’ Disease originating from air-handling and water systems in WA
  • Enable enforcement agencies to respond to potential outbreaks of Legionnaires’ Disease by enforcing control measures

These Regulations are currently under review as part of the Public Health Act 2016 regulatory review program.

Who is required to comply with the Regulations?

The Regulations apply to all buildings across WA except those classified as a:

  • Class 1 – single dwelling
  • Class 2 – 2 or more sole occupancy units; or
  • Class 10 – non-habitable building or structure (e.g. shed)

under the Building Regulations 2012 regulation 6.

Buildings that must comply include (but not limited to):

  • shopping centres
  • office buildings
  • universities
  • hospitals
  • hotels
  • aged care facilities
  • food processing and industrial facilities
  • drycleaners.
Australian and New Zealand Standards

There are several requirements that industry must adhere to under the Regulations.

These requirements are specified in the Australian Standards 3666:

AS3666 Scope of Australian standard
Part 1 Air-handling and water systems of buildings - Microbial control Design, installation and commissioning
Part 2 Air-handling and water systems of buildings - Microbial control Operation and maintenance
Part 3  Air-handling and water systems of buildings - Microbial control Performance-based maintenance of cooling water systems
Part 4 Air-handling and water systems of buildings - Microbial control Performance-based maintenance of air-handling systems (ducts and components)

Australian Standards must be purchased from the Standards Australia website.

Depending on whether the cooling water system can be shut down for periodic cleaning and maintenance, industry may choose to comply with either AS3666 Part 2 or AS3666 Part 3. Part 2 requires shutdown of cooling water systems for periodic cleaning and maintenance. This may be impracticable for many systems, such as large industrial types serving power stations, co-generation plants, oil refineries and chemical manufacturing plants, who can choose to comply with Part 3 instead.

If water testing for Legionella is undertaken, it should be supplementary to and not in place of, good installation, upkeep and maintenance practices as prescribed by Australian Standard AS 3666. Reliance upon routine sampling for Legionella species as an indicator of the need to initiate maintenance procedures does not comply with the Australian Standard or the existing legislative requirements.

Key requirements of the Australian Standards – operation and maintenance

Part 2: Operation and maintenance [for cooling towers that can be shut down for periodic cleaning and maintenance]

Key requirements include:

  • ensure all equipment and components are serviced and maintained
  • ensure equipment can be easily and safely accessed for cleaning, inspection and maintenance
  • ensure cooling towers are inspected at least monthly as part of a regular maintenance program and cleaned when necessary. Cleaning intervals shall not exceed 6 months
  • require operating and maintenance manuals to be provided for all equipment and systems
  • keep up to date maintenance reports and log book and ensure all records are readily available for inspection by an enforcement agency
  • where a system has not been in operation of more than 30 days an assessment shall be carried out within three to seven days of system operation.

Part 3: Performance‑based maintenance of cooling water systems [for cooling systems that cannot be shut down]

Key requirements include:

  • take a representative sample of cooling water at least once a month when the system is in use and test for legionella
  • take a representative sample of cooling water at least once a month when the system is in use and test for heterotrophic microorganisms counts
  • initiate control strategies when:
    • legionella is detected >10 cfu/ml
    • heterotrophic microorganisms is detected>100 000 cfu/ml
  • produce reports detailing test results.

Water systems

Water systems must be maintained in accordance with the requirements of the regulatory authority.

Health and aged care facilities

The design and function of the water distribution system within a health or an aged care facility can affect the potential health risks posed by Legionella within the facility.

Legionella is therefore of significant concern in health and aged care facilities because of the presence of vulnerable people with clinical risk factors that increase both the likelihood and the potential severity of Legionella infection.

Refer to health and aged care facilities for supporting resources.

Occupational safety and health

The Code of Practice - Prevention and control of Legionnaires’ Disease 2010 (Code of Practice) was issued by the Commission for Occupational Safety and Health (the Commission) and its Mining Industry Advisory Committee under the provisions of the Occupational Safety and Health Act 1984 (WA) (OSH Act) and the Mines Safety and Inspection Act 1994 (WA) (MSI Act).

The Code of Practice provides:

  • practical guidance on how to comply with a general duty under the OSH Act and MSI Act or specific duties under the OSH Regulations and MSI Regulations
  • ·non-prescriptive, practical guidance on safe work practices that can be used to reduce the risk of work-related injury and disease and
  • a practical means of following any code, standard, rule, provision or specification relating to occupational safety and health in WA

For further information refer to the Department of Mines, Industry Regulation and Safety.

Building Code of Australia

The Building Code of Australia (BCA) contains technical provisions for the design and construction of buildings and other structures, covering such matters as structure, fire resistance, access and egress, services and equipment and energy efficiency as well as certain aspects of health and amenity. In WA, the BCA is adopted through the Building Act 2011 and the Building Regulations 2012.

The BCA includes the issue of ventilation and providing healthy air to breathe.

  • Clause F4.5 of BCA Volume One requires a mechanical ventilation or air-conditioning system to comply with AS/NZS 3666.1 (and AS 1668.2), where installed in lieu of natural ventilation complying with Clause F4.6.
  • Clause F2.7 of BCA Volume One also requires hot water, warm water and cooling water systems to be installed in accordance with AS/NZS 3666.1. This does not apply to a system serving only a sole occupancy unit in a Class 2 or 3 building or Class 4.

Where a cooling tower system forms part of the mechanical ventilation system or air-conditioning system, it is necessary to specifically check the location of the cooling tower in relation to air intakes, air exhausts and drift control measures, in accordance with AS/NZS 3666.1.

Risk factors for legionella growth

There are a range of environmental risk factors that affect the presence/growth of Legionella bacteria in cooling towers and warm water systems.

Legionella will enter the system, presumably from the water supply. The bacteria then multiply as a result of one or more of the following scenarios:

  • failure to treat the water to an adequate standard, which can be due to:
    • a lack or breakdown of a regular treatment schedule or system equipment
    • a system being shut down for extended periods of time without following appropriate start-up procedures (e.g. lack of water recirculation when the system is not in use)
    • human error
  • environmental contamination of the cooling tower water, for example, by:
    • airborne dust from nearby construction works
    • nutrient availability and growth (algae or biofilm growth)
  • poor design or location of the cooling tower system (e.g.
    • the presences of dead legs in pipework
    • potential for exposure of people to the aerosols of the system
  • inadequate or non-existent maintenance (including plans for replacement of aging cooling tower systems).
Commissioning and start-up of cooling towers

Several outbreaks of Legionnaires’ Disease worldwide have been due to new cooling water systems having been commissioned without prior chemical treatment or cleaning prior to coming into operation. Therefore, commissioning a new system is an important control in preventing outbreaks.

Additionally, when a cooling tower has not been in use for an extended period, stagnant water can create opportunities for legionella to proliferate. If the cooling tower is then operated following a period of non-operation there is a chance of an outbreak occurring if appropriate action is not taken.

Therefore, specific requirements are needed for both commissioning and start-up of a cooling tower. These requirements are outlined in AS3666 Part 1 (Commissioning) and AS3666 Part (start-up).

Responsibility for system maintenance

Water based cooling systems can be complicated and require a level of expertise to be able to effectively prevent a Legionella growth from occurring. It is recognised that an owner of a building may not necessarily be the appropriate person to maintain and operate a cooling tower.

It is important that the owner of a building ensures a competent person who has had appropriate training or practical experience (or both) is responsible for the management and maintenance of cooling towers to ensure compliance with the Regulations.

Many companies will outsource the operation and maintenance to a third-party contractor, engineer or water service provider.

The Department of Health is unable to recommend third party contractors.
Outbreak investigations and inspections

Local government authorised officers have a legislated role with powers to investigate cooling tower systems and enforce compliance with Health (Air-handling and water systems) 1994.

Local government authorised officers play a crucial role in investigating individual cases and outbreaks of Legionnaires’ Disease.

A Legionnaires’ Disease outbreak should be viewed as an immediate priority by a local district.

Multiple authorised officers may be required to support the investigation of a Legionnaire’s Disease outbreak.

It is often very difficult to pinpoint the source of a Legionnaires’ Disease outbreak with accuracy. The main aim of a public health response is to stop the outbreak by ensuring that cooling towers and other possible sources of infection in a location suspected to be the cause of the outbreak are controlled as quickly as possible.

Refer to the Legionnaires’ Disease outbreak investigation protocol for local government authorised officers.