Which is worse, scalded skin or Legionnaire’s disease? Until 2006, many homeowners had to ask themselves that question. It has to do with water temperature. Water in a water heater should be hot enough to kill microbes such as Legionella bacteria. It should also be cool enough that it doesn’t scald your skin. There is a happy middle ground, but it’s surprisingly narrow; 120 to 125 degrees F. There is some controversy about this: OSHA recommends temps at least 140, but the Consumer Product Safety Commission sets the limit to 120. Skin will scald at 130 within 30 seconds.
Adjusting the settings on your water heater is not much more complicated than adjusting the thermostat for the furnace. For older gas models, it comes to turning the black and red dial on the front of the heater. That dial may have numbers or letters. To raise the temperature, turn the dial to the left a little bit. You most likely will need to make additional adjustments as you go. Just give the water heater a few hours to adjust, and check the temperature again.
Newer models, both gas and electric, have the same kind of controls, but they are behind panels. Don’t be concerned; the panels are easy to take off and replace.
Of course, you need to turn off the power at the circuit beaker panel before starting. Remember to turn the power back on when you are done.
Anyway, back to the water heater. Behind the panel, you will see a small piece of insulation. Just pull that out, and put it back when you are done. Using a flat head screwdriver, make adjustments just like you would with the dial.
Electric water heaters have two panels. Change them both the same amount. The top thermostat should be a few degrees higher than the lower one.
Remember to wait at least 3 hours before testing by running hot water over a meat thermometer.
The target temperature is 120 to 125, which is admittedly narrow. To really fine-tune the appliance, consider installing a temperance valve. These devices are easy to install, and are available at home centers for around. $150.00.