How to Adjust the Temperature of a Gas Water Heater

November 30, 2010 | by Ethan (email) |

For some time, one of the items on my to-do list was to adjust our water temperature. This project quickly climbed my  list as colder temperatures have arrived. Fortunately, it’s a five minute job. Here’s a step-by-step guide for adjusting the temperature on a gas water heater. If you have an electric heater, Kim wrote an excellent post detailing how to adjust electric water heater temperatures.

Measuring Water Temperature

Optimal Water Temperature

The Energy Star site, under Sure Energy Savers, recommends setting “water temperature only as hot as needed (110-120 degrees) to prevent scalds and save energy (check local codes for specific temperatures)”. But Todd from Home Construction Improvement made a great point that lower temperatures can lead to promotion of Legionnaires’ Disease. Even the Occupational Safety & Health Administration (OSHA) offers the same opinion in their Legionnaires’ Disease FAQ, although smaller water systems are less likely to become infected. OSHA recommends “water heaters [be set to] 140°F and [should yield] 122°F or higher at the faucet.”

Ultimately, I adjusted our temperature to read 110° at the faucet (check out the picture above). That reading is a little low as the TEK4 IR thermometer isn’t really designed for this application, but we couldn’t find our meat thermometer which is a better choice for measuring water temperatures at the tap. I would guess the temperature is closer to 120°.

Water Heater Blankets

Water heater blankets are a great way to insulate your hot water heater, especially older heaters, but it’s important to leave access to heating elements, combustion air, electric and exhaust. Having the appropriate cut-outs makes it easy to access the water thermostat so keep this in mind while installing.

How To Adjust Water Temperature on a Gas Heater

I am not a licensed plumber and you should follow these directions at your own risk. For this job, you need to be mindful of plumbing, electric and gas so if you’re not up to the task, don’t try it.

Gas Water Heater Cover Gas Water Heater Controls

Here’s how I adjusted the temperature on my gas water heater.

I used a nut driver and flat-head screwdriver. You shouldn’t need anything more than this for your own water heater adjustment.

Locate Thermostat:
Gas water heaters typically have one temperature control near the bottom, sometimes concealed behind a plate (like mine). Unlike electric heaters, you don’t need to switch off any breakers or locate a second thermostat. Electric water heaters will have two temperature controls, one for a top element and one for a bottom element.

Gas Water Heater Thermostat

Remove the Cover:
Using the nut-driver or appropriate screwdriver, remove the cover taking care not to disturb any of the concealed lines. My cover had a diagram that indicated where the thermostat was located. Check any documentation you have if your doesn’t.

Adjust Temperature:
Rotate the thermostat clockwise to increase the water temperature or counter-clockwise to decrease the temperature. Adjust the temperature incrementally to the desired setting to avoid scalding temperatures. Remember to replace the cover when finished.

What do you think? Have any tips to add?

One Response
  1. HANDYMAN51 says:

    I’ve read that insulation blankets don’t really do much for the newr, pre-insulated water heaters, so no need to ” overkill”. Scalding can occur at about 126 degrees Fahrenheit, so stay around 120 degrees, especially if you have little kids or someone with confusion/ impaired sensation using the taps.

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