Thermocouples For Water Heaters: Everything You Need To Know

the master repairs the boiler

Although it’s a crucial component in a gas-powered water heater, a water heater thermocouple isn't really that complicated. The safe operation of a propane or natural gas-powered water heater is insured by a thermocouple. Must you replace your entire water heater if a thermocouple malfunctions? No. It's not very expensive, and actually quite easy to replace a thermocouple.

Let's examine thermocouples, troubleshoot them, and look at replacing one.

Thermocouples: What Are They?

A pilot flame is used in a standing pilot water heater, which burns continuously. The main burner is ignited by the pilot when the system needs heat. There is a thermocouple next to the pilot that generates a small electrical current when the pilot flame heats it.

By preventing the release of unburned gas into your home, the thermocouple acts as a safety switch. When the pilot light goes out, it closes the gas valve. The thermocouple will warm up once the pilot light has been relit, and once again provide the necessary voltage for the gas valve to open.

When Thermocouples Go Bad

There are two metal rods that play a huge role in how a thermocouple works and the electric current that is created (which keeps the valve on your water heater open). If there is a problem with the thermocouple, this is usually where it originates. The necessary voltage isn't being generated by the rods. Since they're so inexpensive, thermocouple replacement is usually the better course of action here, rather than trying to repair the thermocouple.

If you're looking for the thermocouple, you'll find it right next to the pilot light. A couple of clips hold it in place in its bracket.


  • If your pilot light goes out repeatedly, you could have a bad thermocouple.
  • If you notice that you don't have hot water, this could be the first sign of a faulty thermocouple.

Replacing Your Thermocouple

Here's what you'll need to replace your thermocouple…


  • Wrench set
  • Adjustable wrench
  • Flame source with which to relight the pilot
  • Flashlight if lighting is bad


  • Replacement thermocouple (make sure you have the right one)


  1. It's smart to shut off the gas supply to any gas-powered appliance when you work on it.
  2. Along with two gas tubes, unscrew the thermocouple lead.
  3. The burner assembly should be removed and the thermocouple detached.
  4. The burner compartment could be vacuumed out at this time. Also, check burner ports to remove debris, and check for leaks.
  5. The new thermocouple can now be attached and the burner assembly reinstalled.
  6. Turn the gas back on.
  7. Relight the pilot.
  8. Make sure there are no gas leaks.

Water Heating Direct Can Help Answer Questions about Expansion Tanks and More

At Water Heating Direct, we not only provide high-quality water heaters, but any water heater accessory you’ll likely need. From concentric vent kits to condensate neutralizer systems and from pigtail kits to installation kits, we've got you covered.

To assist you while working on your water heater, we provide not only a page from which you can download technical documents, but we have a special applications/engineering team designated to assist our customers with any issues or inquiries they may have. The last thing you need is the run-around from some customer-service person when you're in the middle of a water heater emergency. We get it!

Before you shop for water heaters or accessories anywhere else – and before you tackle a problem without at least the offer of technical assistance – check out Water Heating Direct. We beat the competition with honest pricing, service plans, specials, and so much more.

If you'd like to reach out to us, please feel free to use our convenient online form to open the lines of communication. You can also phone us at 401-552-HEAT or email us at