Setting the water heater temperature

Correction: I mentioned in a previous column that you could buy replacement house numbers at Ace Hardware. This is not correct. For the past few years, a Sun City resident, Richard, had a business supplying and installing numbers, lights, and the mounting plaque. Richard gave up his business this year and the Mobile station at Drendel Corner took over selling the parts to Sun City residents. Sorry for the incorrect information.

Question: How to I correctly set the water heater temperature? I believe it should be set around 120 degrees.

Answer: Years ago the recommended hot water temperature was 140° F, but that was only for the dishwasher for proper disinfection and cleaning. Today’s dishwashers pre-heat the water to the proper temperature, so this high temperature is no longer needed.

According to the US Department of Energy, a temperature of 120 degrees at the tap is adequate for most household chores with a minimal danger of scalding and maximal energy efficiency. You can measure this by turning on a hot water tap and running the water until you are getting hot water. Fill a glass with this water and put a thermometer into the water to measure the temperature. A cooking thermometer will work for this. If the water is too cool, turn the temperature control knob on your water heater one notch hotter. Measure the temperature again after four or more hours. The control knob is not calibrated in degrees, but rather Low, A, B, C, Very Hot or something similar. On my water heater I get 120°F water with a setting of ‘B.’

When the temperature at the tap is 120°F, the temperature in the tank will be about 130°F, which is enough to prevent bacterial growth. If your water heater is now set to 140°F, note that you can save 3% to 5% of the energy consumption for each 10°F you lower the temperature.

If you are expecting a houseful of guests, you can increase the capacity of your water heater by turning the temperature up one or two notches. With the water temperature hotter, you will mix less hot water with the cold thus assuring everyone a hot shower.

Be prepared to replace your water heater after 10 to 15 years. They usually fail by leaking water through a hole formed by corrosion in the bottom of the tank. When your water heater reaches that 10-15 year window, you should check it at least once a week as the initial leak will usually be small but the leak will get larger as the corrosion advances. When replacing your water heater, always replace the expansion tank, as these tanks seldom last even as long as the water heater.

If you have suggestions for future tips or have questions about maintenance around your home, submit them to

Comment on This Story