This bacterium, responsible for Legionnaires’ disease, can develop in hot water systems when certain conditions are favorable: inadequate temperature control, stagnant water and the presence of rust, scale or limescale deposits.
Legionellosis is a respiratory infection that can cause fever, coughing, breathing difficulties and, in some cases, serious complications in more vulnerable individuals, such as the elderly or immunosuppressed people. It is important to understand that the bacterium is transmitted mainly by inhalation of fine droplets of contaminated water, which can be generated by showers and faucets, and not by drinking water.
Although Quebec regulations only govern the management of Legionella in water-cooled cooling towers (WCTs), domestic and institutional hot water systems are also environments conducive to its development.
Contrary to popular belief, water heated to 50°C is not sufficient to effectively control bacterial growth in such equipment. To limit its proliferation, water heaters should be maintained at at least 60°C, particularly in retirement homes, hospitals and other establishments catering to vulnerable clientele.
Many people turn down the temperature of their water heaters to reduce the risk of scalding or energy consumption. However, the use of thermostatic mixing valves makes it possible to maintain a safe temperature in the system while reducing the temperature at points of use. As a result, point-of-use water temperatures can be adjusted to no more than 49°C for domestic systems and no more than 43°C for healthcare establishments or private homes for the elderly.
Proper system maintenance also helps to reduce risks:
– draining, cleaning and periodic maintenance of water heaters;
– limiting scale and corrosion build-up;
– reducing water stagnation in little-used pipes.
Lab’eau-air-sol offers analysis of Legionella in drinking water to support building managers, healthcare institutions and commercial and industrial organizations in their efforts to prevent and control water quality.