Cooling Towers and Warm Water Systems are a high risk manufactured water system and must be operated in accordance with the SA Public Health (Legionella) Regulations 2013, Australian and New Zealand Standard (AS/NZS 3666) and Guidelines for the Control of Legionella.
Owners of Cooling Towers and Warm Water Systems are required to register their system within one month of commissioning and registration must be renewed annually.
In accordance with the Public and Environmental Health (Legionella) Regulations 2008, owners of high risk manufactured water systems (HRMWS) must report to their local Council within 24 hours of receiving a report indicating the presence of Legionella:
- at or greater than 10cfu/ml in a warm water system
- at or greater than 1000cfu/ml in a cooling water system
Cooling towers act as a component of some air-conditioning systems or as cooling devices for some plant processes and equipment.
Large quantities of organic material and other debris may accumulate in the water as a result of the air being scrubbed as it passes through the plant.
Films containing different micro-organisms form on surfaces and provide food and shelter for the growth of Legionella.
The Legionella bacteria can multiply and flourish in this artificial habitat and are then widely dispersed by aerosol, possibly causing infection.
Almost all Legionella outbreaks have involved air-conditioning plants or warm water systems which have been incorrectly commissioned or have been poorly maintained.
Illnesses attributed to Legionella (covered by the general term 'legionellosis") may take two forms:
- Pontiac Fever - a non life-threatening 'flu-like illness lasting several days; and
- Legionnaire's Disease - a severe, often fatal form of pneumonia.
- Construction material should be able to withstand high-pressure cleaning and corrosion.
- Towers should have easy and safe access for maintenance.
- Air inlets should be located away from sources of contamination, eg kitchen exhausts, and airflow should be unrestricted.
- Air exhaust should be located away from occupied areas, eg pedestrian thoroughfares.
- Drift eliminators should be fitted with an efficiency that will reduce drift below 0.02%.
- Towers should be easily drained and refilled.
Cooling towers operated only seasonally shall be thoroughly cleaned and flushed before start up.
Towers should be inspected at least monthly and cleaned as necessary. The cleaning interval shall not exceed six months.
All internal wetted surfaces of the tower, particularly the sumps and fill, shall be cleaned by high pressure water, steam, or other pressure water, steam, or other effective method.
Biocides should provide a broad-spectrum control of micro-organisms.
Records kept by the owner on the premises should include information on:
- Layout of system.
- Operating procedures.
- Maintenance, cleaning and disinfection procedures, and their frequency.
- Name and contact number of person or company responsible for servicing the tower.
Cooling Tower Waste Water
It is important that all cooling tower water be stopped from entering the stormwater system because it is a breach of the:
- South Australian Public Health Act, 2011.
- Environmental Protection Act, 1993.
- Environment Protection (Water Quality) Policy 2003.
The stormwater system leads straight to our rivers and environmental harm can result from the extremely high levels of chemicals in the cooling tower water.
Possible sources of water from cooling towers are:
- Bleed-off valves.
- Drainage pipes.
- Overspray (drift).
- Overflow (faulty ball valves).
- High pressure cleaning.
- Leaking cooling tower.
- Undersized tundishes.
To protect the stormwater system you can temporarily block relevant stormwater drains and then use a wetvac to remove the excess water and or re-engineer the system so that overflows are less likely.
It is also important that any chemicals used are stored to prevent leaks or spills into the stormwater system.
For more detailed information refer to
- AS/NZS 3666 parts 1, 2 & 3 'Air-handling and water systems of buildings - Mircrobial control'.
- HB32 - 'Control of microbial growth in air-handling and water systems of buildings'.
or visit the Department of Health website.
Warm Water Systems
Warm Water Systems are usually located in childcare centres, primary and secondary schools, nursing homes and other health care facilities. They operate with the use of a temperature controlling device that allows the system to distribute or recirculate water through the pipework at approximately 45oC. Whilst the cooler water temperature reduces the risk of burns and scalding, it can increase the risk of Legionella in the distribution system.
Owners of warm water systems will be issued with a annual notice from Council requiring that they engage a competent person to inspect the system and undertake microbiological testing.
Further information can be obtained from SA Health or from Council's Environmental Health Services Division on 8372 8816.