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Every homeowner wants a fully functional hot water heater, providing them with consistent and reliable household comfort. Of course, it’s equally important for the water heater to be safe, not placing the home at any risk of fire or flood. As such, today’s water heaters come with a number of built-in safety features, with the thermocouple being one of the most important.

It’s important for homeowners to know what the thermocouple is, to understand what it does, and to be on the lookout for any issues. If you do find that your thermocouple isn’t working as it should, that’s a clear sign that you need to call a team of water heater repair professionals.

In this post, we’ll answer some of the most common questions about thermocouples, and offer some more general insights into how to troubleshoot potential water heater problems.

male engineer repairing a gas boiler

What is the Thermocouple?

Simply put, the thermocouple is an important safety device, one that you can find on pretty much all gas water heaters. The thermocouple is basically just two strips of metal, attached near the pilot light as part of the burner assembly. If the pilot light ever fails then the thermocouple will close off the gas valve automatically, preventing unburned gas from spilling out and risking an explosion.

How Do I Know if the Thermocouple Isn’t Working?

There’s really just one telltale sign of letting you know when the thermocouple isn’t working, and that’s when the pilot light won’t stay lit. If you experience this problem, it’s important to have your thermocouple assessed as soon as possible.

What Happens if the Thermocouple Fails?

So what are the consequences of a failed thermocouple? Long-term, it increases your personal risk, significantly elevating the possibility of a hazardous explosion. But in the short-term, a failed thermocouple means you won’t be able to keep the pilot flame lit.

What Causes a Water Heater Thermocouple to Fail?

There are two main reasons why your thermocouple might fail. The first is age. For the most part, your thermocouple is more likely to fail once it takes on some wear and tear. Additionally, thermocouples can sometimes fail due to manufacturer defects.

Can a Water Heater Work without a Thermocouple?

You might wonder: Can a gas water heater even function without a thermocouple? The short answer is no. Without the ability to keep a pilot flame lit, your unit won’t be able to supply the comfort you’ve come to depend on.

Can I Clean the Thermocouple?

If your thermocouple shows obvious signs of wear, you can take just a few minutes to clean it, potentially extending its lifespan. The best way to do this is to use a dollar bill to sand away any areas that exhibit visible oxidation.

As for how often the thermocouple should be cleaned, we recommend roughly once every six months or so.

How Can I Test My Thermocouple?

Usually, if your thermocouple isn’t working, you’ll know it. But if you want to test it to ensure it’s still in good health, we recommend that you use a multimeter to test it. It should read between 650 MV-1000 MV.

How Can I Fix My Thermocouple?

When a thermocouple goes bad, homeowners naturally want to know how to fix it. Unfortunately, this component cannot be repaired. The only real option is to replace it. (You may also consider replacing the entire water heater if it’s more than 10 years old. A skilled plumber can tell you more about the expected water heater repair cost.)

How Long Should My Thermocouple Last?

There’s really no set lifespan for a thermocouple. They typically last for the life of the water heater itself, which may be anywhere from 10 to 15 years.

Additional FAQ About Thermocouples

If you have any specific concerns about your thermocouple, or about the safety of your water heater, we recommend contacting a water heater repair professional. Additionally, here are a few further questions from homeowners.

How do I know if I need a new thermocouple?

The best way to verify that you need a new thermocouple is to see if your pilot light is lit. If the pilot light can’t hold ignition, that means either a problem with the gas supply or, more likely, the need for thermocouple replacement.

How do you test a thermocouple valve?

Again, use a multimeter and test. It should read between 650 MV-1000 MV.

How often should a thermocouple be cleaned?

Manufacturers recommend inspecting every six months.

Kelson Carter

Article reviewed by:

Kelson Carter, aka, The Prince of Plumbing

Kelson is a 3rd generation Plumbing Contractor. His family business is located in Greenwood, Indiana, and provides Residential Plumbing Service to the Indianapolis Metro market.

Kelson grew up watching his grandfather and father do plumbing. After graduating high school, Kelson went to Trade School and became a Licensed Master Plumber and Licensed Plumbing Contractor. He is also Certified in Backflow Prevention. He currently owns and operates Carter's My Plumber with his parents.


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