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Heated Debate About Hot Water

Feb 2, 2005 | Home & Community Safety

This archived article is from June 2005. Although every effort has been made to make sure the information presented is accurate, please note that it may contain information that is out-of-date.

In most Canadian homes, hot water heaters are set at 60 C (140°F). For many years that temperature has been the standard. However, water at 60 C can cause third-degree burns in most adults in six seconds. Third-degree burns are the most serious kind; they damage all layers of the skin.

Tap Water Scalds

Young children, with their delicate skin, can suffer a serious hot water burn in as little as one second. The elderly and those with disabilities are also more susceptible to severe scalds. Scald injuries can be agonizingly painful. For a toddler, a serious scalding can require years of skin graft surgery. An elderly person may even die in the aftermath of a scalding.

The Canadian Hospitals Injury Reporting and Prevention Program (CHIRPP) analyzed 830 cases of scald injuries among children who visited participating hospitals in 1999. While CHIRPP does not detail the severity of injuries, the treatment data indicate scald injuries were often serious. A much higher than average number of the scald patients required follow-up (66 percent, compared with 34 percent for all injuries in the 1999 database). Admissions were also significantly higher (10 percent, compared with seven percent for all injuries).

Hot beverages and hot food accounted for 73 percent of all scalds. Hot tap water was responsible for seven percent, and children under five sustained three-quarters of those injuries.

As a way to prevent scalds, injury prevention advocates have lobbied to have settings on domestic hot water tanks reduced to 49 C from the accepted 60 C standard. A few jurisdictions outside Canada mandate the 49 C setting, and have seen a decrease in scalding injuries.


In 2000, the Walkerton disaster had sent a wake-up call about the safety of Canada’s drinking water. While standards for domestic hot water must consider scald prevention, they must also address the broad spectrum of public health and safety issues. To minimize bacteria contamination, water must be stored at 60 C or higher.

For example, temperatures under 50 C may increase the risk of Legionnaires’ disease, a form of pneumonia, due to bacterial growth in the tank. That disease is caused by Legionella bacteria, which live in water. Temperature is a critical factor for Legionella to grow. The risk of colonization in hot water tanks is significant between 40 and 50 C.

Legionella bacteria most often enter the lungs due to aspiration. (Aspiration means choking such that secretions in the mouth bypass the choking reflexes and enter the lung.) Drinking contaminated water is not a major cause of Legionnaire’s disease.

The Centers for Disease Control and Prevention estimates 8,000 to 18,000 Americans contract the disease annually. Five to 30 percent of the cases are fatal. While Canada has no national statistics, Hydro-Québec says about 100 people a year are hospitalized in that province for pneumonia caused by contaminated residential water heaters.

Plumbing Code Changes on Hold 

In 2001, the Canadian Commission on Building and Fire Codes (CCBFC) was informed that the Canadian Medical Association had passed a resolution urging provincial and territorial governments to amend existing building and plumbing codes to require the default setting of new residential hot water heating devices to a maximum of 49 C in order to address the safety of children and elderly who were being scalded in significant numbers.

The CCBFC asked the Standing Committee on Building and Plumbing Services to examine the scalding issue and to recommend changes to the National Plumbing Code of Canada.

The Standing Committee on Building and Plumbing Services has the responsibility to balance concerns about all known risks into its decisions. The Code process must scrupulously examine every possible impact of proposed changes. This level of precaution and consensus is critical to the health and safety of Canadians.

The Standing Committee did not recommend the lower maximum temperature for hot water heaters. Instead, it proposed a maximum 49 C hot water temperature at fixture outlets in residential occupancies with the exception of installed dishwashers or clothes washers. Automatic compensating mixing valves at each fixture, or a master mixing valve, could be installed to meet the objective. The change, which would only apply to new construction, was to appear in both the National Plumbing Code (NPC) and the National Building Code (NBC) in 2005.

In 2003, during the public consultation on proposed changes for the 2005 NBC and NPC, industry and some provincial governments opposed the committee’s proposal. Those most likely to be held responsible for illness from contaminated water still had concerns.

In October 2004, after much discussion and consultation, the CCBFC withdrew the proposed change. It requested a national task group be set up to examine the health and safety risks associated with hot water delivery in buildings. The task group has reviewed the medical knowledge, statistics and circumstances of Legionella contamination, as well as information about injuries related to scalding. Its recommendations and a proposed course of action have been submitted to the Standing Committee on Building and Plumbing Services for consideration.  That committee meets at the end of June 2005 to review the proposals of the task group, and will make recommendations on this matter to the CCBFC.

Tips for Taps

The country’s top experts, represented on the CCBFC, have rejected the lower maximum hot water tank temperature of 49 C. In spite of this, trusted organizations are telling homeowners to lower their hot water tank temperature to 49 C as a precaution against scalds from tap water. Some even offer tips on how to find the thermostat so you can adjust it yourself.

The issue is controversial and confusing. What is the best advice?

The bottom line is that water must be stored at a high temperature as a precaution against bacteria. It can be delivered from the tap at a lower temperature to prevent scalds.

Most people reduce the temperature as the water comes out by mixing hot and cold water.  The basic precautions are common sense.

  • 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.
  • Turn the cold water on first, then add hot water until the temperature is comfortable.
  • Teach children to turn the cold water on first, and the hot water off first.

If the water that comes out of your tap is too hot, you can install valves in the plumbing lines to reduce the temperature of the water delivered at the tap by mixing in cooler water. Another option is to install anti-scald devices at individual taps; they slow the water to a trickle if it gets too hot.

In homes with small children or elderly occupants, it may be appropriate to turn down the temperature of the hot water tank. For those who feel compelled to do so, the Canada Safety Council recommends a temperature no lower than 54 C. Be sure to check your local building and plumbing codes before doing so, as some regions may have minimum requirements in excess of 54 C. If you are unsure how to make the adjustment, hire a qualified professional such as a plumber to do the job.

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