Water Heater Thermal Switch Keeps Tripping? (Possible Causes & Fixes)

Matthew Mountain
by Matthew Mountain

Water heaters are essential in modern homes, and luckily, they are usually easy to rely on. However, they are made of several parts that work together, and just one malfunction can throw the whole system off. So, what should you do when your water heater thermal switch keeps tripping?

A water heater’s thermal switch keeps tripping if a vent is blocked. Excess heat will build up within the system, and you’ll need to clean one or both of the vents to increase the airflow. A thermal switch can repeatedly trip on a water heater a thermostat or the heating element is damaged.

You can generally inspect your water heater and diagnose the problem without professional help. However, it is ideal to hire a plumber if there is a blockage deep within either of the vents. Follow along as we explore why your water heater thermal switch keeps tripping.

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Why Does my Thermal Switch Keep Tripping on my Water Heater?

There are several reasons why a water heater thermal switch keeps tripping, and it’s often due to a blocked vent. However, a thermal switch can trip if there is a problem with the thermostat, wiring, breaker, or reset button. It may require some troubleshooting, but you can use this guide to save you some time and trouble when your water heater thermal switch keeps tripping.

Thermostat Error

Your system likely has two thermostats if it runs on electricity. There is generally one thermostat on the upper part of the system and another at the bottom. The upper thermostat generally contains a reset button that comes in handy when your thermal switch keeps tripping on your water heater.

There are two thermostats included because there are two heating elements. These elements are never on at the same time as a safety measure to ensure that the water inside the tank doesn’t get too hot. Water heaters contain thermostats because they measure the water temperature so it can shut on or off when necessary.

Your water heater will malfunction if one or both thermostats go bad, and this can cause the thermal switch to trip.


When your system has malfunctioning thermostats, replacement is necessary. A professional plumber will help you replace your thermostats, as they’ll know which thermostats are compatible with your system.

Heating Element Burnt Out

The heating element is what brings the water in your heater to the correct temperature. Water heaters have a metal casing that is generally durable, but they can suffer damage. This typically happens when the heating element burns out, but the casing can deteriorate over time.

While most gas heaters only utilize one heating element, electrical systems have two. Therefore, electrical heaters are twice as likely to experience element-related issues.

Power will continue to run to the heating element even if there is a short in the system. In this case, water will continue to heat until it reaches 180°F. When this temperature is reached, the thermal switch will trip, and the water will not get any hotter.


This is another problem that will likely warrant component replacement. Again, you should get help from a professional plumber when you need to replace your water heater’s heating elements.

There’s Something Wrong With the Reset Button

The thermal switch is a reliable safety mechanism, but if it keeps tripping, then it’s likely this component is faulty. As was explained earlier, a thermal switch is included to cut off power in the event that the water inside a heater’s tank exceeds 180°F.

However, as time goes on, a thermal switch will wear down, and eventually, it will struggle with reading the temperature of water inside the tank. When this happens, the thermal switch might shut off power at the wrong time, like when the temperature of the water inside the tank is completely fine.


To fix this problem, a plumber will have to replace the thermal switch as well as the upper thermostat it’s connected to. Again, this is the case only with an electrical heater that utilizes two thermostats. Some systems don’t include thermal switches that are attached to thermostats, so fixing this issue in such systems may be more difficult.

Faulty Wiring

An electrical problem may be causing your water heater to not work properly. Specifically, if you have loose wiring, this cannot only be hazardous but it could also be causing your thermal switch to trip unexpectedly.

When wiring is loose, excess heat will be produced, and then this will cause the water heater’s thermal switch to trip. It’s good that a water heater’s thermal switch can prevent the loose wire from disrupting how the system functions, but if loose wire causes the thermal switch to keep having to be tripped, eventually the switch may wear out.

There are other wiring issues to look out for. Specifically, if you have aluminum wiring and copper wiring in your water heater, you may utilize a special plug connector to connect these wires.

If the plug connector is not in place, the two metals may cause the water heater’s breaker to trip. There’s also the possibility that a breaker is out, and if this is the case it’s likely the thermal switch will trip when you don’t want it to.


When you’re dealing with an electrical issue, it may be best to get an electrician to look at your water heater. A plumber may not be able to fix the wiring or breaker-related issues, and therefore an electrician will be required.

Blocked Vent

A blocked vent can pose a risk to your entire water heater system and home. The water heater cannot get enough air if there is a blockage in the vent, and it will cause your thermal switch to trip. Heat can accumulate within the system and your water heater will trip the thermal switch as a safety measure.

The average water heater has a vent at the top and bottom of the unit. You may be able to spot the blockage if you inspect either vent, but blockages are often lodged deeply.


Shut off power to your water heater, let it cool down, and clean the vents. Contact a plumber if you cannot access the blockage so that the problem doesn’t continue. Restore power to your water heater and reset the unit after you clean it so that your thermal switch doesn’t continue to trip.

Get Professional Help

Now it’s time to clean the flame trap. This is beneath the burner on the inside of the combustion chamber; you’ll need to turn off the gas before you do this. Next, vacuum the inside of the combustion chamber once you get access to it, and pay close attention to the bottom of the chamber.

If during this time you smell gas, immediately stop what you’re doing and open all the windows and doors in your home. A gas leak can be very dangerous, and you’ll want to get experts out to your property to deal with this ASAP.

This is why a DIY thermal switch reset is not recommended. Instead, you should get the help of a professional plumber when you need to reset your water heater’s thermal switch.

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Related Questions

When a water heater shuts off because it has become too hot, this can be an alarming situation. Moreover, there are so many different water heaters out there these days, and most systems run differently in this situation. Here are the common questions that are asked about water heaters and the thermal switches they utilize.

Can a water heater’s thermal switch trip because there’s not enough air?

If your system isn’t getting enough air, this may result in the thermal switch being tripped. Some water heaters—like hybrid water heaters for example—utilize air to heat water.

When there’s not enough air available, your system won’t be heated in this way, which means it will have to rely on the backup power burner, and this may heat the water to a temperature that’s too high, therefore tripping the thermal switch. To avoid this situation, make sure your hot water heater is in a spot where there’s plenty of room.

Does a broken thermal switch mean thermostat replacement is necessary?

You’ll need to replace the thermostat if the thermal switch trips frequently. It is ideal to hire a professional plumber to replace your thermostat.

Matthew Mountain
Matthew Mountain

Matt loves everything DIY. He has been learning and practicing different trades since he was a kid, and he's often the first one called when a friend or family member needs a helping hand at home. Matt loves to work with wood and stone, and landscaping is by far his most favorite pastime.

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