Can you guarantee there’s no risk of Legionnaires’ disease during Hilo challenges?

Only a water heater specifically designed to prevent Legionella could fully eliminate the risk of Legionnaires’ disease at all times. Currently, no such water heater is available on the Québec market.

Legionella is a naturally occurring bacterium that exists in low concentrations in freshwater sources. The risk arises when it finds its way into man-made water systems — like hot tubs, cooling towers, and water heaters — where stagnant, warm water (between 32°C and 45°C) creates the perfect environment for it to grow. Legionnaires’ disease occurs when people inhale tiny droplets of water containing the bacteria, such as those released during a shower.

The risk of exposure to Legionella exists regardless of Hilo challenges, especially in older water heaters where lukewarm water may accumulate at the bottom of the tank. This risk is higher if the water temperature drops too low — particularly during longer showers when hot water runs out.

Hilo challenges are designed to reduce electricity consumption during peak demand periods by temporarily shifting certain energy-intensive activities — like heating water — to off-peak hours. To help prevent hot water shortages during these periods, the Hilo temperature sensor monitors the water at the top of the tank.

If it detects a temperature drop during a challenge, the water heater automatically restarts to bring the water back up to a safe level, reducing the risk of exposure to lukewarm water from the bottom of the tank. Certain precautions (alt : Simple actions) — like limiting shower time to avoid drawing lukewarm water from the bottom of the water heater (alt : tank) — can help minimize (alt : reduce) the risk of Legionnaires’ disease year-round.

The National Plumbing Code recommends maintaining a minimum water heater temperature of 60°C to prevent bacterial growth. However, it’s also recommended not to exceed this temperature, as higher settings increase the risk of scalding.

For more information on how to prevent Legionnaires’ disease, visit: https://www.quebec.ca/en/health/health-issues/a-z/legionellosis