How to Set Water Heater Temperature

Water Heater Temperature Bend ORWhen it comes to setting the water heater temperature for your home’s water heater there are several factors to consider other than personal preference..  Manufacturers’ requirements, appliance requirements, and at risk groups are important factors to be considered as well.

Some manufacturers require a thermostat set at 140 F, yet most households require only a setting of the thermostat at 120 F.

Some appliances, usually a dishwasher without a booster heater may require a setting between 130 F and 140 F for optimum heating.

Water heater temperature above 130 F can pose a safety hazard for certain at risk groups such as small children, disabled or elderly residents.

There are two main and opposing risks:

  • Too high, and users get scalded
  • Too low, and you risk pathogens, particularly Legionella, which causes legionellosis (Legionnaires’ disease)

According to the US Department of Energy, a temperature of 120 F at the tap is adequate for most household chores with a minimal danger of scalding and maximal energy efficiency.  However, that is the temperature at the tap, not in the tank.  Tank temperatures should be no less than 130 F to prevent bacterial growth such as Legionaire’s Disease.

Minimum Water Heater Temperature

According to the paper Legionella and the prevention of legionellosis, found at the World Health Organization website, temperature affects the survival of Legionella as follows:

  • Above 70 °C (158 °F): Legionella dies almost instantly
  • At 60 °C (140 °F): 90% die in 2 minutes
  • At 50 °C (122 °F): 90% die in 80–124 minutes, depending on strain
  • At 48 to 50 °C (118 to 122 °F): Can survive but do not multiply
  • 32 to 42 °C (90 to 108 °F): Ideal growth rang

It is always good to test your water heater temperature at the tap.  This can be done with a simple cooking thermometer and a deep glass. Just wait for the water to run fully hot and then fill the glass and measure.

If you need help with this decision, or if you are concerned that your water heater is not performing as it should, call us your local Bend, Oregon plumbing expert. A qualified professional can advise you on proper settings, and can recommend the ideal water heater for your needs.

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