September 28, 2026
If you live in the Bay Area and you’re dealing with water heater issues, it could be due to a faulty thermostat, which can cause your water heater to run inefficiently or stop working altogether.
When it’s time for a water heater thermostat replacement, it’s important to know how to do it safely and correctly. Learn the signs to look for that may indicate your water heater thermostat is failing, common thermostat-related problems, how to replace it, and when to call on the highly skilled plumbers at Service Champions for help.
A water heater thermostat is a temperature-activated switch that continuously monitors and regulates the temperature of the water you use in your Bay Area home. The exact mechanism and how it works depend on which type of water heater you own.
An electric water heater thermostat uses a surface-mounted sensor that’s pressed tightly against the exterior of the metal tank. These thermostats use a disc made of two different metals that snap open or closed as the metals expand when heated. Most electric water heaters have two thermostats, one for each heating element. The upper water heater thermostat is the main controller that heats the top of the tank first, then redirects power down to the lower water heater thermostat and element.
A gas water heater uses a mechanical probe thermostat that sits inside the water tank. This thermostat has a copper tube and an inner rod made of a different material. As the water temperature rises and falls, the tube and rod expand and contract, pushing or releasing a lever that opens or closes the gas valve. When it detects cold water, it opens the valve and allows gas to flow to the main burner to heat your water supply.
Most water heater thermostats need to be replaced every 10 to 15 years. Before you replace your water heater thermostat, look for these signs that it may be failing:
Before beginning any water heater troubleshooting or making a water heater temperature adjustment, it’s important to take a few safety precautions:
Identifying upper and lower thermostats on your electric water heater depends on the wiring setup, their location on the tank, and the presence of the red reset button. For most water heaters, the upper thermostat is located behind the main access panel and features a large, red reset button. The lower thermostat is typically located behind the bottom panel and doesn’t have a red reset button.
If you have a gas water heater, we recommend hiring a professional plumber to replace your water heater or thermostat. Before replacing an electric water heater thermostat, gather these tools:
Water heater thermostats sense the temperature of the tank or the water inside, which automatically signals the heating element or gas valve to turn on or off. Electric water heater thermostats are located outside the tank and sense the water temperature through conduction. Gas water heater thermostats sense the temperature via a special probe submerged directly inside the tank.
Not all hot water problems are related to the thermostat. Many parts of the Bay Area have hard water, which causes sediment buildup that affects other components, such as the lower heating element. A cracked or broken dip tube can affect water heater performance, and a faulty thermocouple on gas water heaters also poses problems. If the hot and cold pipes are accidentally cross-connected in your home, it can cause cold water to bleed into the hot water lines.
In an electric water heater, the thermostat is the central control that determines when and how hot water is supplied, and the heating element converts electricity to heat. Both components work together to maintain a safe, consistent water temperature.
The thermostat is placed just outside the tank to monitor and control the temperature, and when the water drops below the set temperature, it triggers a switch that powers the heating element. When the top of the tank is heated, the upper thermostat turns off the top element and redirects power to the lower thermostat and heating element.
All upper thermostats have a high-limit safety switch that trips and cuts power to the unit and heating elements when the water gets too hot.
Occasionally, testing your thermostat is a good part of water heater maintenance. Follow these steps to ensure you test it correctly:
When testing the upper thermostat, if the meter reads near zero, the switch is good, but if it reads “OL,” the switch may be tripped or broken. When testing the contacts, if the meter reads OL at all times and doesn’t fluctuate between zero and OL, the thermostat is faulty.
Avoid these common mistakes when replacing your water heater thermostat:
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