How Hot Should Your Hot Water Be?

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This is one of those questions that have existed for a hundred years and yet no single “right” answer really exists. Following government directives, which were created for storage tank systems, we are told to keep our tanks in the 120°F to 125°F range. This temperature, though more than hot enough to pose a scalding danger, is commonly quoted as it is the lowest temperature at which most water-borne pathogens are destroyed or kept under control. Most of us do not know that a storage water heater, if not kept sufficiently hot, provides an ideal environment for bacterial growth. Hot, moist, non-turbulent and dark, bacteria have all the essential elements for growth. Bacterial blooms are commonplace in many water heaters – especially if they are set to “vacation” mode, or shut-off entirely.

Whether because of the desire to kill bacteria or the desire to simply have “more hot water for the shower”, many Americans turn their water heaters up to maximum – typically 140°F. As can be seen from the scald-chart below this temperature can be very dangerous as severe burns will result from only 3 seconds direct skin exposure at 140°F!

Hot water is dangerous, especially for children, elderly, or people in poor physical health. Even brief exposures to water temperature over 125° F can cause severe burns:

  • 3 seconds at 140°F (60°C)
  • 20 seconds at 130°F (54°C)
  • 8 minutes at 120°F (49°)

Most storage tank water heaters have wide heat/reheat cycling temperature swings that can cause water temperature to vary significantly during the day. A common example of this is a cold morning shower caused by water cooling over night – but not sufficiently cooling so as to trigger the heater to re-heat the water. Often the hottest shower of the day is the second shower in the morning once the tank has reheated (recovered) from the first shower! As such, ALWAYS check the water temperature by hand before entering the shower or bath. The temperature may have changed from your prior shower/bath use. Additionally, do NOT leave children, elderly or people of poor physical health unsupervised in a bath or shower. Across America every year many thousands of people are severely injured when users accidentally adjust a faucet causing the water temperature to increase to unsafe/dangerous levels thereby causing, typically children and the infirm that cannot exit or react, to be exposed to scalding water.

?When setting your tank water heater we recommend a setting of 125°F as sufficient and safe for most residential applications. If you have children in your home you may wish to adjust the temperature down to 120°F to avoid scalding issues.

Tankless water heaters are a completely different breed than a storage water heater. Tankless water heaters only heat water when it is needed. Tankless energy efficiencies are gained by the fact that tankless heaters (1) only heat water when hot water is needed, and (2) only heat water to a comfortable/desired temperature.

One significant advantage that tankless water heaters offer is that most have virtually no water storage capacity, and what small amount of water that may remain in the heater when not in use is not heated. Because of this there is no concern about bacterial growth. As a result, when using tankless water heaters it is not necessary to overheat water to the point where blending cold water is needed to reach a comfortable temperature. Instead, most tankless models allow the user to set a comfortable temperature of 104°F to 110°F and the heater will produce this water temperature for so long as needed. As such it is not necessary to turn up the heat to get a longer hot shower.

Many tankless units available today even have remote temperature selectors that automatically turn down the temperature when a children’s bath for example is needed. Skye’s FORTIS branded tankless water heater has a full graphic LCD display that allows the user to set an operating temperature from 90°F to 140°F by simply adjusting a digital thermometer in one degree increments. Skye, like many other manufacturers, recommends that the heater be set at a “comfortable” level – and not unnecessarily hot as this simply increases operating costs. Simply put, tankless water heaters provide a safe, comfortable and efficient solution to most every families hot water needs.

If you have any questions regarding the tankless water heater settings, contact your manufacturer or go to our website at www.tankless.com or contact one of our representatives at 1-877-888-SKYE; we’d be glad to help.

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