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Check Water Heater Temperature

Materials Cost: FREE
Difficulty Level: 1

Introduction

Turning your water heater temperature down to 120°F can promote safety, save energy, and improve system efficiency.

Why

The U.S. Environmental Protection Agency recommends setting water heaters at 120°F to prevent scalding. Every 10-degree reduction also saves about 5% in energy consumption. By turning the temperature down on your water heater, you can promote safety, save energy, and it may help your water heater last longer by slowing down the build up of mineral deposits and corrosion.

What You'll Need

  • Coffee mug or glass measuring pitcher
  • Flathead screwdriver
  • Meat Thermometer
  • Water heater manual

1. Determine water heater setpoint.

Start by checking your water heater’s current temperature. This step can also help you check whether the temperature setting on your water heater matches the delivered temperature of your hot water. To find the current temperature of your hot water:

  1. Get a coffee mug or glass measuring pitcher and a meat thermometer and go to the faucet nearest to the water heater.
  2. Turn on the hot water tap only and run the water for about 3 minutes to ensure hot water is being pulled from the tank. 
  3. Fill the mug with hot water from the tap.
  4. Immediately place the meat thermometer in the mug and take the temperature reading (Figure 1). Use a meat thermometer, not the kind of thermometer you use to take your own temperature. Older style mercury fever thermometers can break if exposed to temperatures over 110°F.

  5. Note the temperature. If it is well over 120°F, you can adjust it down to 120°F to reduce scalding risk, save energy, and increase the life of your equipment.

     

Figure 1. To test the water heater’s temperature, draw hot water from a faucet near the water heater for three minutes, then fill a mug with hot water from the tap and check the temperature with a meat thermometer (Source: Mason PUD 3, 2012).

2. Turn off the breaker.

Find the water heater on your electrical panel and flip the breaker to off. If you have a gas water heater, this should not turn off the pilot light.

3. Adjust the temperature.

  1. Find the temperature adjustment on your water heater. The temperature controls may be on a controller box attached to the front of the water heater tank (Figure 2) or they may be behind a protective panel on the tank (Figure 3). If you don’t see them, consult your owners’ manual. If you no longer have the manual, pdfs of many appliance manuals can be found on line by searching your appliance brand and model number.
Figure 2. This water heater has the temperature settings on a control box attached to the front of the water heater (Source: PNNL).
Figure 3. On some water heaters, the temperature controls are behind an access panel; if the water heater has two access panels, remove both panels to check and set temperature controls (Source: Mason PUD 3, 2012).
  1. If the temperature controls are behind a panel, unscrew the panel. Typically these panels are held in place with one screw at the top. If there is more than one panel, open both access panels and look for temperature controls at both locations.  
  2. Some water heater temperature controls show temperature numbers, some use letters or another designation. To determine what temperatures correspond to the letters, check your owner’s manual (Figure 4).
Figure 4. When setting the temperature on your water heater, refer to the manual for your model to determine what letter designation on the thermostat dial corresponds to the temperature setting for 120°F (Source: PNNL).
  1. Adjust the temperature to 120°F using a flathead screwdriver or by turning the knob by hand (Figures 5 and 6).
Figure 5. To adjust this water heater’s temperature, turn the dial to 120°F with a flathead screwdriver (Source: Mason PUD 3, 2012).
Figure 6. To adjust this water heater’s temperature, turn the knob on the controller; refer to the owner’s manual to determine what setting corresponds to 120°F (Source: PNNL).

4. Turn on the breaker.

Go back to your electric panel and flip the water heater breaker back to on. 

Additional Info

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Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.