How to Adjust Your Water Heater’s Temperature

Be safe—keep the water heater temperature setting at 120 degrees F.

Every year, hospital emergency rooms see people with burns caused by their tap water. Why? Because the temperature on their hot water heater is set too high.

Hot water has become something that we just can’t live without, whether it is being used to clean things around the house or just a relaxing shower after a long day on the job. But it’s important to know where the threshold is. What is the reasonable and safe upper limit for the hot water heater in your home?

What Temperature Should a Water Heater Be Set At?

The Department of Energy recommends a hot temperature setting of 120-degrees. There are two reasons for that, safety and energy savings.

Most hot water heaters have a default setting of 140 degrees, which is far higher than you really need it to be. No wonder that a hot water heater can account for as much as 18 percent of the average household utility bill. Turning it down to the recommended 120 degree temperature setting can save some money, as much as $400 per year.

The default temperature of 140 degrees can also be dangerous, posing a risk for scalding. Burns can occur with as little as six seconds of exposure to water at 140 degrees, according to the Consumer Product and Safety Commission, and young children and the elderly can be more susceptible.

The only time you might want to consider a temperature in the range of 130 to 140 degrees is if you have a dishwasher that does not have a booster heater. Anyone with a compromised immune system of chronic respiratory disease might also consider a higher temperature on their hot water heater. There is a slight risk for legionellae bacteria at 120 degrees, but the level is still considered safe for the majority of the population.

How to Adjust the Temperature on a Hot Water Heater

Finding the temperature setting on a water heater can sometimes be difficult, because most dials aren’t labeled with numbers. For under sink hot water heaters and tankless hot water heaters, the temperature control device might look different than the one pictured here, so check your owner’s manual for how to adjust the temperature on those.

If the stickers on the water heater don’t tell you how to set the temperature and you can’t find the owner’s manual, use this method:

  1. Run hot water at the tap closest to the water heater for at least three minutes.
  2. Fill a glass and check the hot temperature.
  3. If the water is above 120 degrees, adjust the dial, wait about three hours and check again.
  4. Repeat until your water temperature reads 120 degrees.

For a final test, check the water heater temperature the following morning before anyone uses any hot water. Make a mark on the dial once you find the correct setting so that you don’t have to go through this testing process again.

Finally, when you’re conducting your routine hot water heater maintenance, always check the temperature setting to make sure it’s where it should be.