There are two risks inherent with the temperature of household hot water scalds and bacteria.
For many years in Canada the standard setting for hot water heaters has been 60°C (140°F). The problem with the 60°C setting is that it can scald adults in six-seconds and the delicate skin of children in half that time. Persons with disabilities and the elderly are also susceptible.
As a way to prevent scalds, injury prevention advocates have lobbied to have settings on domestic hot water tanks reduced to 49°C. The problem with setting the tank to 49°C is that it is low enough to promote bacteria growth.
Exposure time at given temperatures that cause second-degree burn injury in adults
°C °F Exposure time
49 120 9 minutes
51 124 2-6 minutes
52 125 2 minutes
55 131 20-30 seconds
60 140 5-6 seconds
Most people reduce the temperature of the water as it comes out of the tap by mixing hot and cold water. The basic precautions are common sense
The B.C. Building Code mandates that direct hot water equipment be capable of heating water at least to 45°C but not above 60°C.
To find out what temperature your hot water is, wait two hours after your last hot water use. Turn on the hot water tap in your bathroom and let it run for 3 minutes. Fill a cup with the hot water and place a thermometer in it that can show high temperatures.
While the standards for domestic hot water temperatures should consider scald prevention, they should also address health and safety issues. To minimize bacteria contamination, water must be stored at 60°C or higher.
Temperatures under 50°C promote bacterial growth in water and may increase the risk of diseases. Temperature is a critical factor for Legionella bacteria growth. The risk of colonization in hot water tanks is significant between 40 and 50 C.
What is the best advice?
Keep the temperature of stored water at 60°C and reduce the temperature at the tap to 49°C.
If the water that comes out of your tap is too hot for your liking, you can install valves in the plumbing lines to reduce the temperature to the taps while keeping the tank at the right temperature. Another option is to install anti-scald devices at individual taps they slow the water to a trickle if it gets too hot.