How to Set the Thermostat for an Electric Hot Water Heater

Water heaters are among the most frequently used appliances in a home, but because they are tucked away in a closet or in a corner of the garage we don't think about them very often. They can be very hazardous if the temperature is set too high. Children and the elderly are frequently scalded by hot water from a water heater that was set too high. If you cannot comfortably hold your hand under the tap with the hot water turned on, then you should adjust the water heater temperature. This is a simple process that only takes a few minutes.

Things You'll Need

• Phillips head screwdriver Flathead screwdriver 1/4-inch or 5/16-inch nut driver Flashlight

Instructions

1. Turn off power to your water heater at the breaker.

2. 

   Find the maintenance access covers on your water heater. There should be two, one about a foot below the top of the water heater and one near the bottom.

3. 

   Remove the covers by unscrewing the retaining screw or screws.

4. 

   Use caution not to touch any live wires. (Always assume that exposed wires are live, even if you turned off the power, unless you have verified that they are not energized by using a voltmeter or multitester.) Then remove or push aside the fiberglass insulation under each access cover. Save the piece removed because you will need to put it back when you are done.

5. 

   Find the thermal control. See figure 4 for examples of thermal controls. There should be one under each access cover.

6. Using a flathead screwdriver, adjust the temperature setting. There should be markings to show which direction will increase the temperature and which will lower it. Some thermal controls indicate temperature settings, others just indicate "Warm" or "Hot."

7. Match the upper and lower settings.

8. Replace the insulation and the maintenance access covers.

9. Turn on power to the water heater at the breaker.

10. Run the water for several minutes to cool the water in the tank enough to ensure the thermostat energizes the heating elements.

11. Wait about 15 minutes for the heater to reach it's maximum temperature. If you have been using hot water or you had the power shut off for an extended period, you may need to wait longer. If all the hot water in the tank was used up, it could take more than an hour to reach the maximum temperature.

12. Test the water with your hand or a thermometer. The maximum temperature produced by the water heater should be around 120 degrees Fahrenheit. If it is over 125 degrees, then go back to step 1 and adjust it again.

Tips & Warnings

• Thermostatic valves are available that can be installed into the hot water line above the water heater. These sense the temperature of water leaving the heater and, if it is too hot, mix cold water into it to control the temperature. This type of valve is becoming very popular and is even required by law in some places, but few older homes have them. If you don't have one in your home, then you need to make sure that your water heater is set to a safe temperature. If you cannot comfortably hold your hand under the tap with the hot water turned on, then you should adjust the water heater temperature. This is a simple process that only takes a few minutes.

• Warning! Thermostat settings above 120 to 125 degrees Fahrenheit (49 to 52 degrees Celsius) are extremely dangerous and can easily result in serious or even fatal burn injuries from scalding. Do not set your water heater for temperatures above 125 degrees Fahrenheit (52 degrees Celsius) unless you have a thermal control valve installed that will mix colder water in with water heater hot water to keep the household water supply within the desired range.

References

• WiseGeek on Water Heater Temperature Settings
• Tap Water Scalds: Safety Alert