How to Adjust the Water Temperature of a Hot Water Boiler

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Adjust the water temperature of a hot water boiler.

Hot water is a necessity for any functioning household. Hot water is mainly used for showers, washing clothes and cleaning dishes. Sometimes the temperature of the water coming out of the faucet or shower is too hot or not hot enough. The United States Department of Energy recommends that hot water should be a minimum of 120 degrees coming out of the tap and 130 degrees Fahrenheit at the tank. To avoid taking a lukewarm shower or being scalded while rinsing dishes, you'll need to perform a simple adjustment of your hot water boiler.


Step 1

Test your tap water temperature. Allow the water to run until it is fully hot and fill up a tall glass. Hold a cooking thermometer in the water and take a temperature reading. The water should be a minimum of 120 degrees Fahrenheit. If it is less, adjust your hot water boiler upwards. If the temperature is well above 120 degrees, you can safely adjust your hot water heater downward slightly before testing again to be sure you maintain the recommended minimum temperature at the tap.


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Step 2

Adjust the thermostat. If you have an electric water heater, turn off the power before removing the metal plate that houses the thermostat. There could be live electrical wires and components so turning off the power is crucial before removing the metal plate. Once the plate is removed, use a screwdriver to adjust the thermostat. If your electric hot water heater has two thermostats, one on top and one on the bottom, both should be adjusted to the same temperature.


Step 3

Turn the knob on the side of the tank. If you have an oil-powered water heater, there will be a knob on the side of the water tank. Find this knob and turn it slightly before testing the tap water temperature. Continue turning the knob slightly to make incremental adjustments in the water temperature until it's as hot as you want it to be.


Step 4

Rotate the thermostat control. If you have a gas hot water heater, first locate the temperature control. On many gas water heaters, the temperature control is located near the bottom of the tank. On some, it can be found behind a metal plate. Rotate the thermostat control slightly before testing the tap water temperature. Continue rotating the control until you reach your desired hot water temperature.


The U.S. Department of Energy's recommended minimum tank temperature is 130 degrees Fahrenheit to prevent the growth of any bacteria.

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