Legionnaires' disease and reducing the risks

There are many different types of Legionella bacteria found in the environment. Legionnaires’ disease from water is usually caused by the species Legionella pneumophila.

Legionella pneumophila must be inhaled for Legionnaires’ disease to occur and generally infects the lungs causing pneumonia. You can only become infected if you inhale small airborne droplets of water or aspirate drinking water containing the bacteria.

Legionnaires’ disease typically infects the lungs and can cause severe pneumonia. 

See Legionella pneumophila for more information including signs, symptoms and treatment.

Common sources of infection

You can become infected with Legionella pneumophila through various manufactured water systems including: 

  • cooling towers
  • hot and cold water taps
  • showers
  • therapeutic nebulisers and humidifiers
  • chilled water dispensers
  • car washes
  • misting devices
  • spa baths
  • hydrotherapy pools
  • ornamental fountains
  • home birthing pools.

Legionella will grow in devices containing warm water (25oC to 50oC).

Cooling towers and hospital and aged care warm water systems are required to be operated in compliance with strict regulatory requirements to reduce the risk of Legionella growth. However, Legionella pneumophila is often found in common household sources during Legionnaires’ disease case investigations, indicating that many sporadic (single case) infections occur in private homes.

Reduce the risk of Legionnaires’ disease

Below is information on how to control Legionella pneumophila in common sources found in and around the home:

Hot water systems and reducing the risk of legionnaires’ disease

Hot water storage tanks should be set to store water at 60oC or greater to reduce the risk.

If you are unsure of how to set the temperature of your hot water tank, seek advice from the manufacturer or a plumber.

This temperature may be too hot for water to be supplied to showers and taps used for washing, as it may cause an unacceptable scalding risk. This concern applies particularly where children or older people wash.

If it is necessary to lower the water temperature to 45oC to 50oC to reduce the risk of scalding, this can be achieved by installing water temperature controlling devices called thermostatic mixing valves near the outlets.

If the temperature of the hot water system falls, the thermostat may be malfunctioning and may need repair or adjustment.

Hot water systems and filter devices attached to shower heads should be
maintained regularly according to the manufacturer’s instructions.

Hot water taps and reducing the risk of Legionnaires’ disease

All warm water taps that are not used on a daily basis should be flushed weekly.

To flush them, simply turn the tap on at full flow with hot/warm water for at least 15 seconds once they reach correct operating temperature.

Flushing will help eliminate stagnant water and minimise the multiplication of bacteria that may be present.

Spa pools and reducing the risk of Legionnaires’ disease

Spa pools require careful maintenance, disinfection and frequent cleaning because they provide ideal conditions for the growth of Legionella pneumophila, and aerosols can be created when spa pool jets are in

The correct use and maintenance of a spa pool can keep spa pool water in a clean, safe and healthy condition. 

Spa pools and their jets should not be used if:

  • the disinfectant level and / or pH is outside the recommended range
  • the pool water is dirty or cloudy
  • the filtration unit and recirculation pump are not operating correctly.

Refer to Spa pools, maintaining your spa at home for more information on spa pool maintenance.

Spa baths and reducing the risk of Legionnaires’ disease

Spa baths should be drained after each use, inspected frequently, and regularly
cleaned and maintained to ensure hygienic operation. The entire system should be kept dry when not in use.

Therapeutic nebulisers and humidifiers and reducing the risk of Legionnaires’ disease

It is recommended that only distilled or preboiled (sterile) water is used in therapeutic nebulisers and humidifiers to reduce the risk of bacterial growth.

Nebuliser bowls should be rinsed after each use, and the entire chamber and mask washed daily in warm water and dishwashing liquid, rinsed and all components allowed to air dry.

After each use, humidifiers should be emptied and the tank, mask, headgear, tubing and connectors should be cleaned in warm water and dishwashing liquid, then rinsed and all components allowed to air dry.

Pumps should be serviced and filters changed regularly, in accordance with the manufacturer’s instructions.

Fountains and reducing the risk of Legionnaires’ disease

Fountains can create aerosols by splashing water, and are a particular risk if the water is warm or heated intermittently by submerged lighting. Regular draining, cleaning and disinfection is recommended.

Evaporative air conditioners and reducing the risk of Legionnaires’ disease

Although there have been no reported cases of Legionnaires’ disease connected with the use of domestic evaporative cooling systems, correct maintenance is essential to control the accumulation of sediment, bacteria, mould and algal growth inside the unit. Growth of these organisms in the system can cause hay fever or allergic responses. When the system is in
use you should:

  • ensure that an adequate bleed-off rate is maintained to prevent dissolved solids and impurities from accumulating inside the unit
  • dispose of bleed-off water safely by connecting bleed-off water into a sewerage system or, if in an unsewered area, discharge to soakage areas such as flower beds or lawns. Bleed-off water should never be discharged into gutters which run into drinking water tanks
  • inspect and clean the unit regularly to maintain effective and safe operation.

At the end of summer:

  • drain all water in the unit from the tank and pipes
  • clean the tank and pump filter with a cloth soaked with a chlorine-based household bleach solution and flush with clean water
  • dry the internal components, leave the drain-cock open and fit covers to
    exposed units for off-season storage.

Before the start of summer:

  • remove the external covers drain all water in the unit from the tank and pipes
  • remove the filter pads and thoroughly clean the filters by hosing with water
  • renew the filter pads as necessary
  • close the drain-cock and fill with clean water and check that the unit is operating correctly.

Portable evaporative cooling units and reducing the risk of Legionnaires’ disease

Portable evaporative cooling units should be completely drained at least once a week during the summer season.

When units are not being used for an extended period they should be completely drained and cleaned, and left to dry.