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My Water Heater is Getting too Hot

When your hot water is too hot, it can cause harm in seconds or potentially break the water heater. We’ll discuss common reasons for the sudden temperature increase and how to change the thermostat on different water heaters.

Reasons your water heater is getting too hot

Broken Thermostat

A water heater works the same as a heating and cooling system. Without the thermostat telling the heating element or burner when to turn off, they’ll continue warming the water to extreme levels.


Start by checking the current set temperature. It should be between 120 and 140 degrees Fahrenheit with 140 being the factory setting. Lower the temperature between 15 and 20 degrees then wait two to three hours. Run hot water from a faucet or tap and check the temperature with a thermometer — a meat thermometer is fine.

If the thermometer temperature is higher than the set temperatures, the issue is likely the thermostat. It’s also possible the thermostat isn’t secured against the water tank. Check again and if it is loose, realign and tighten the screws.

2. Mineral Buildup

Hard water is an unpleasant fact of life for 85% of the United States. It leaves behind mineral deposits without help, but when heated, more calcium and magnesium deposits are left. As the deposits coat the inside of the water heater, it can’t appropriately sense the water temperature. This creates the situation for scalding water.

Regular water heater maintenance is a good way to avoid excessive buildup, including having the system fully flushed once a year. A trained plumber will also look for potential clogs and other buildup issues during this appointment.

3. Faulty Heater Element

Electric water heaters rely on one or two heating elements to warm the water to the appropriate temperature. But, like other electrical components, these elements will ground or fail with time. The automatic shut off usually stops working when its grounding and the heating element continues to heat the water to an unsafe level.

4. Issues with the Pressure Relief Valve

The pressure relief valve allows a tiny amount of steam and water to be released from the water heater if the temperature or pressure inside approaches unsafe levels. Otherwise, the hot water can create enough internal pressure to cause the tank to leak or explode.

Test the valve’s function by lifting the valve opening a few times then listening for a gurgling noise. If you hear this, or see a tiny trickle of steam or water, good — it’s working. If not, or you hear a different noise, contact a trained plumber as soon as possible.

How to Change the Water Heater Thermostat

A hot shower or bath after a long day sounds relaxing, but if the water is too hot, you or someone else could be scalded or burnt in a matter of seconds. Children and elderly adults are more susceptible due to fragile skin. And even an adult can receive third-degree burns in two seconds or less if the water temperature is at or above 150 degrees Fahrenheit.

On the other hand, the temperature shouldn’t be set below 120 degrees Fahrenheit. Any lower and illness-causing bacteria, such as Legionella, have an environment to develop.

Gas Water Heater

If you have an older gas water heater, look for a dial thermostat near the bottom of the tank. Adjust the temperature with the dial and test the water temperature if you want.

Newer gas-powered units keep the thermostat behind an access panel on the side of the tank. You’ll need a standard screwdriver to remove the panel and adjust the thermostat.

  1. Turn off the water heater’s power source, such as at the circuit breaker.
  2. Locate the access panel and use the screwdriver to remove it from the tank.
  3. Remove any insulation inside the panel.
  4. Use the screwdriver to adjust the thermostat temperature.
  5. Replace the insulation inside the panel and reattach the panel.
  6. Turn the power back on at the circuit breaker.
  7. Relight the pilot light if necessary.
  8. Wait two to three hours after adjusting the thermostat to test the water temperature.
  9. Adjust the thermostat as necessary.

Tankless Water Heater

Tankless water heaters have the easiest thermostat to change. That’s because most models use a digital control panel quite similar to your heating and cooling system — press a button or two and the temperature is changed.

How Long Will My Water Heater Last?

Water heaters with a tank usually last up to 10 years with regular service and water heater maintenance. Tankless styles may reach 20 years before replacement is needed. Speak with a trained plumber if you think your water heater is nearing replacement; they’ll have the best insight into whether it’s necessary.

A water heater is meant to warm the water and deliver it through faucets and taps in your home, but not water so hot it causes injury and damage to appliances. Need your water heater checked? Call Proskill today for an inspection.




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