Hot Water Heater Overheating: Causes & Fixes

Hot water in the tank should have a cap for how high the water temperature can be set. Hot water can scald people if there’s no safety mechanism in place to prevent the water heater from overheating.

In order to keep your hot water heater healthy, you need to ensure your water heater doesn’t get hotter than normal.

How Do Hot Water Heaters Work?

Two popular types of water heaters are gas and electric. They both serve the same purpose but vary in how the water is heated.

And although each are designed to heat water and retain that heat, your water heater should not feel too hot to touch. If it does feel hot, it likely has an insulation problem.


Gas water heaters use a burner to heat the water in the tank. These burners are located in the center inside the gas water heater. The burners will heat the water to the temperature set on the thermostat and then when the water reaches that temperature, the burner will simply shut off until the water cools again.

For a gas water heater to operate effectively, it will require:

  • Tank
  • Combustion
  • Air Flow

Gas water heaters transfer heat to the water using combustion of either natural or liquid propane gas. Typically, a burner in a combustion chamber ignites the gas through the use of a pilot light. Water heaters with gas burners also require airflow to remove carbon dioxide fumes from the home.


Electric water heaters are more efficient than gas-powered ones. They use a heating element placed in the water that is triggered when the temperature falls below a certain level.

The electricity is passed through the resistant material and turned into heat, which then heats the water.

Causes and Solutions for a Water Heater Overheating

If your water heater is making hot water too hot all of a sudden, it’s likely the result of the temperature setting being too high, a malfunctioning thermostat, high mineral content, or the pressure relief valve is blocked. Each of these issues can cause the water from the faucet to come out too hot.

Temperature Setting Too High

Water heaters have dial indicators that allow you to control the temperature of the hot water. This is usually set between 90- and 120-degrees Fahrenheit, but this could be too high for some homes.

Check the thermostat and adjust lower if necessary. Sometimes the dial is accidentally tweaked too high, so this troubleshooting solution to fix your water heater is the first step in diagnosing a water heater overheating problem.

Electric water heater

On most residential models, there will be both an upper and lower thermostat and they should be adjusted to the same temperature. To test which of the thermostats might be defective, allow the water heater to sit for about half an hour after running a generous amount of hot water.

The electric water heater will cycle the elements and stabilize the temperature. Turn off the power and remove the two access covers on the thermostats.

Pull the insulation aside and ensure that the thermostats are adjusted to the same temperature and are making full contact to the wall of the tank. Full contact is essential for proper temperature regulation.

Take a small flat blade screwdriver and adjust the dial to the highest setting and then back to the lowest setting. Listen for an audible click when the thermostat contacts open and close.

Alternatively, you can use a multimeter to monitor the continuity as you rotate the dial.

If a thermostat does not appear to open the contacts when turned to a lower setting, then it should be replaced.

Disconnect the wires and lift up on the spring mounting bracket to remove the thermostat. Make sure that when installing the new thermostat, the mounting bracket maintains a firm contact between the thermostat and the tank.

If you are not comfortable with performing this maintenance yourself, contact a water heater technician.

Gas water heater

The temperature is controlled by the gas valve. The valve assembly will have a dial that will allow for temperature adjustment and will also have a probe that monitors the water temperature.

If adjusting the dial does not achieve the desired water temperature, then the valve assembly must be replaced.

Malfunctioning Water Heater Thermostat

A malfunctioning thermostat is most likely the culprit of why your water heater is suddenly hot or feels too hot too touch. A thermostat controls the on and off cycle of water heater elements. In the case of a malfunction, a safety feature is triggered if the thermostat fails to shut off power to the boiler elements during routine cycling.

Should the reset button activate, no power flows to the heating elements, which results in a loss of hot water for the home.

However, if the thermostat or safety mechanism fail to work properly, the elements continue to heat the water. This may lead to unsafe temperature levels of your hot water. However, a thermostat can easily be replaced.

High Mineral Content

Not all minerals will be filtered out in most home water purification processes. These minerals can conglomerate when the water is heated and sink to the bottom of the water heater or settle around the heating element.

A gas water heater will not be working as efficiently if there is sediment in the tank because they heat from the bottom of the tank. When the bottom has a layer of hard sediment, the heat will take longer to transfer through the layer of sediment to your water. 

When these heating elements get coated with sediment, they have to work harder to heat the water. This can lead to the elements overheating, which is why your water heater is suddenly scalding hot.

The water can absorb this heat, but it can cause your water heater to overheat. This also decreases the lifespan of the inner heating elements which will deteriorate faster.

Pressure Relief Valve Blocked

The pressure relief valve allows steam that has built up to escape from inside the water heater. If this valve is blocked, it is probably the reason why your hot water and hot water heater are hotter than normal. This can lead to a damaged tank and serious injury to you and your family.

If you can hear water boiling inside your water tank, you need to shut down the power to your water heater immediately. A blocked pressure relief valve could lead to a water heater explosion. Call a plumbing professional as soon as possible after shutting off your water heater.

Nothing is Too Hot to Handle for the John C. Flood Team

If you’re facing issues with your hot water heater, or any other part of your home’s plumbing system, be sure to schedule an appointment with a plumbing expert from John C. Flood as soon as possible by calling 703-214-5611.

We’re even offering $75 off water heater installations.

Keep your family safe and warm — but not too warm — with a properly functioning water heater. Our team takes extra special care of your water heater to save you money.

This Month's Special

$75.00 OFF

Any Plumbing Service

Minimum of $500.00 job to be applicable. Cannot be combined with any other offer or discounts. Limited time offer. Coupon must be presented at the time of the initial call. Discounts/promotions cannot be applied.

Expires: 04/30/2024

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