Legionella: what is it?
Legionella is the name of a bacterium, resistant to chlorine, that thrives in stagnant water at temperatures between 25°C and 45°C.
Legionella: where is it found?
Legionella can proliferate in household hot-water systems and in air-conditioning systems. Certain types of household equipment and building facilities can cause propagation of the bacteria:
faucets and shower heads fed directly by a typical household water heater;
humidifiers;
spa and hot tubs; and
poorly maintained cooling towers in buildings.
How can Legionella affect my health?
Legionella causes Legionnaires’ disease (also called Legionellosis), which, luckily, is a rare occurrence in Quebec. It is potentially fatal, however. There are a variety of possible symptoms: high fever, chills, cough, fatigue, muscle pain, loss of appetite, diarrhea, nausea, and, unfortunately in about 15% of cases, death.
The risk of contracting Legionellosis is low among the healthy population. Men and people aged over 50 are those must vulnerable, especially those who:
- smoke;
- drink alcohol in large quantities or often;
- sare living with chronic illnesses (diabetes, lung, heart or kidney disease);
- and/or have weakened immune systems.
Good to know
The mere presence of the bacteria in water is not sufficient to cause infection. The contaminated water must be dispersed in the air as tiny droplets (i.e., an aerosol); inhaling the bacteria in the droplets leads to infection.
How do I keep Legionella out of my house?
The Quebec Construction Code stipulates that water-heater thermostats must be set to ensure a temperature of at least 60°C to prevent Legionella from multiplying. To prevent the risk of scalding, however, the Code also states that, for new plumbing installations, the outlet water temperature in a bath or shower must not be higher than 49°C. This is achieved by means of mixing valves (of the thermostatic or pressure-balanced type, depending on the situation) installed on faucets.
Follow these tips to lower the risks related to Legionella:
Never lower the thermostat temperature of your water heater;
If your water comes from a well with hard or ferrous water, drain the water heater once a year;
Ensure proper maintenance of devices that release microscopic drops of water into the air, like shower heads, spas / hot tubs, and humidifiers;
Use an evaporative humidifier instead of an ultrasonic model;
Don’t shut off the water heater if you are leaving home for only a few days;
If you are leaving for an extended period of time (like a long trip), shut off the water inlet to the house, shut off the water heater, and let the taps in the house run to reduce the water pressure. When you return, turn the water back on and let all the taps run to refill the water heater and all pipes.
If you have a spa or hot tub and you are leaving home:
for more than two weeks, it’s best to drain it;
for a few days only, lower the water temperature, but leave the filter running.
Where can I learn more about Legionella?
Health Canada: Legionella
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