Any water system, with the right environmental conditions, could be a source for Legionella bacteria growth. There is a reasonably foreseeable Legionella risk if your water system:
• has a water temperature between 20–45 °C,
• creates and/or spreads breathable droplets, e.g. aerosol created by a cooling tower, or water outlets,
• stores and/or re-circulates water,
• is likely to contain a source of nutrients for the organism to grow, e.g. rust, sludge, scale, organic matter and biofilms.
The most common sources of Legionella are in man-made water systems including:
• cooling tower and evaporative condensers,
• hot and cold water systems,
• and spa pools.
There are also a number of other potential risk systems that may pose a risk to exposure to Legionella, e.g. humidifiers, air washers, emergency showers, indoor ornamental fountains etc.