It is necessary to adjust hot water heater settings periodically throughout the year. Water coming into the tank is colder during the winter. When adjusting hot water heater settings it is important not to adjust the temperature too high as this can cause scalding. At the same time, avoid setting the temperature too low and allowing the growth of spores resulting in Legionnaires Disease. Ideally a temperature of 125-degrees is safe for most children while not resulting in growth of spores inside the hot water tank, especially electric units. Most manufacturers set the temperature at 140-degrees because most homes now use anti-scald faucets. Avoid temperature settings above 140-degrees. Most hot water heater settings do not have actual numbers on the thermostat. It is recommended that you first find out what the true temperature of the hot water is before adjusting the settings.
Check The Water Temperature
Turn on the hot water at a faucet closest to the hot water heater. Allow the water to run for five minutes to bring the water to its highest temperature. After five minutes, fill a glass with the hot water and turn off the faucet.
Place a thermometer such as a cooking thermometer into the glass of water. Check the temperature on the thermometer after one minute. Ideally you want a temperature reading between 125-degrees and 140-degrees. If you have small children or older adults in the house, it is a good idea to lower the temperature to 125-degrees. You can place the hot water heater setting at 140-degrees, however it is a safe practice to install water mixer valves either at the faucet or tank to avoid scalding.
Adjust Electric Hot Water Heater Settings
Turn off the circuit breaker to the hot water heater if you have an electric unit. Depending upon the size of your hot water tank you might have one or two thermostats. Look for the thermostat access panels on the side of the tank. Remove the access panels with a Phillips-head screwdriver and pull the panels away from the water heater tank.
Pull any insulation away from the thermostat so you can access it clearly. Some manufacturers place a plastic shield over the thermostat and heating element. Pull the plastic shield away for full access.
Turn the dial thumb screw one notch clockwise with a flat-head screwdriver to raise the temperature. To lower the temperature, turn the screw counterclockwise one notch. If you have an upper and lower thermostat, turn both to the same notch.
Place the plastic shield and the insulation back over the thermostat. Secure the access panels back onto the side of the tank. Flip the circuit breaker to power the hot water heater and wait three hours for the temperature setting adjustment to take place. Check the water temperature as you did originally. Continue making adjustments as necessary.
Adjust Gas Hot Water Heater Settings
Go to the gas hot water heater tank and find the thermostat control knob. The knob is on the face of the gas control valve.
Turn the knob dial to the right with your fingers to increase the temperature or to the left to lower the temperature setting. Move the dial in small increments.
Allow three hours to pass before checking the water temperature. Recheck the temperature using the glass and thermometer. Continue making adjustments as necessary