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About The House
Newer hot water heater thermostats are not calibrated for exact temperature, they rely on general settings.  (Photo: Contributed)
Newer hot water heater thermostats are not calibrated for exact temperature, they rely on general settings. (Photo: Contributed)

How hot should your hot water be?

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I took advantage on the long weekend to do a little hot water tank temperature research. I asked several people what the temperature of their hot water was. None of them knew. Next, I asked them what the temperature should be. They didn’t know that either.

There are two risks inherent with the temperature of household hot water scalds and bacteria.

Scalding

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

  • Turn the cold water on first, then add hot water until the temperature is comfortable
  • Never leave a child alone while drawing water in a bathtub, and check the water temperature before putting your child in.
  • Test the water temperature before bathing or showering.

    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.

    Bacteria 

    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. 


  • Read more About the House - Hugh Cairns articles

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    About the Author

    When you need advice or guidance with for DIY home improvement and repairs, Hugh Cairns can help you with the answers.

    Home improvements can be rewarding and turn your home a nicer comfortable place to live and increase its value. Whether you are renovating your kitchen, converting a loft, giving a room a lick of paint or making improvements to your home’s energy efficiency this column is here to guide you with some useful information and key things to remember.

    Do you have a renovation question or concern? Please feel free to send Hugh your questions. Contact him through www.subject2homeinspections.com





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    The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet presents its columns "as is" and does not warrant the contents.


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