Hot water makes life more comfortable, but screaming hot water coming from the tap or shower can be dangerous. We’ll discuss reasons for the excessively hot water and how to change the temperature on your style of water heater.

If The Water is Too Hot, Does This Mean I Need to Replace the Water Heater?

Not necessarily. Most conventional water heaters with a tank are meant to last eight to 10 years, sometimes longer with regular water heater maintenance and repairs. Tankless styles can last up to 20 years.

Reasons your water heater is getting too hot

Broken Thermostat

When the thermostat doesn’t tell the burners or heating element when to stop heating the water, these components simply carry on because they don’t know any better. Thermostats wear out and malfunction after years of use. But it’s easy to check and see if it’s working.

Start by looking at the current temperature — unless you or a plumber adjusted the temperature after installation, it’s likely still at the factory setting of 140 degrees Fahrenheit. Then, lower the temperatures by 15 to 20 degrees and wait two to three hours. When the time is up, use a thermometer to measure the tap water temperature. If it’s higher than the thermostat setting, the water heater thermostat has likely gone kaput, and you’ll need to call a plumber to replace it.

Unbalanced Thermostat

On the other hand, the thermostat may have become unbalanced or loose from the side of the tank. It needs a tight mount to accurately read the water temperature and to communicate with the burner or heating element. You can use a standard screwdriver to loosen the screws, realign, then snuggly secure it again.

Mineral Buildup

Eighty-five percent of the United States has hard water and by extension, deals with mineral buildup in water using appliances, such as the water heater. When hard water heats up, it leaves behind calcium, magnesium, and other mineral deposits which begin to coat the inside of the tank. As the coating builds, the thermostat can’t appropriately sense when the desired temperature has been reached so it tells the heating mechanism to continue heating the water.

Since hard water is a way of life for many homes, a full water heater flush is a good way to reduce the mineral buildup in both tank and tankless systems. It’s recommended to flush the system every year.

Faulty Heater Element

Electric-powered water heaters use one or two heating elements to warm the water. Given the workload these components handle during their lifespan, they eventually begin to wear and ground out, or fail. A failing heating element won’t turn off when the thermostat says to and produces excessively hot water until it simply dies and stops working altogether.

Issues with the Pressure Relief Valve

Also called the temperature and pressure relief (TPR) valve, this small opening on the side of your water heater is a key safety feature. When water heats up, pressure and steam are created as byproducts. If these begin to approach unsafe levels, the TPR valve opens and releases a small amount of steam and sometimes a trickle of water as regulated. If it malfunctions, water temperatures and pressure continue to rise to dangerous levels while the tank itself may burst.

You can check the TPR valve by moving the opening up and down — you should hear a gurgling noise and maybe see a tiny bit of water released. If not, or there are different noises, contact a trained plumber immediately.

How to Change the Water Heater Thermostat

It’s important to keep the water heater temperature set between 120 degrees and 140 degrees Fahrenheit for two reasons. First, if the water temperature goes below 120 degrees, illness-causing bacteria including Legionella have good conditions to develop. Second, water above 140 degrees can cause scalds and burns in seconds, especially for children and the elderly. It only takes two seconds for an adult to receive third-degree burns with 150 degrees Fahrenheit water.

Gas Water Heater

Depending on how old your gas water heater is, it may use a dial or a protected thermostat to adjust the temperature. If you have a dial, it’ll be near the bottom of the tank and have temperature markings.

If you see what looks like an access panel on the side of the tank, the thermostat is behind it — you’ll need a standard flathead screwdriver to remove the panel and adjust the temperature.

  1. Turn off the water heater’s power source; we recommend the circuit breaker.
  2. Locate the thermostat access panel and remove the screws with the screwdriver.
  3. Remove the insulation to view the thermostat.
  4. Some water heaters have two thermostats; if it has two, adjust the top thermostat to a higher temperature than the bottom one.
  5. Tuck the insulation back over the thermostat and reattach the access panel.
  6. Restore the power to the water heater.
  7. Relight the pilot light, if necessary.
  8. Wait two to three hours then test the water temperature from a tap, and adjust the temperature as necessary.

Tankless Water Heater

Because tankless water heaters only heat the water on demand, it’s a bit easier to adjust the water temperature. The vast majority of models have a digital control panel, similar to a heating and cooling thermostat. Use the panel buttons to adjust the water temperature to what you want.

If your water heater is producing excessively hot water and adjusting the thermostat doesn’t work, contact a plumber to troubleshoot and resolve the issue.

Need help with your water heater? Book an appointment today with a JW Plumbing, Heating and Air professional.

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