How to Clean a Thermocouple in Water Heater (7 Step Guide)

Last Updated On October 19, 2021
how to clean thermocouple on water heater

Is your pilot light going out unexpectedly? A dirty or malfunctioning thermocouple may be the culprit. 

How do you know your thermocouple is bad? And how do you clean a thermocouple in a water heater? 

This PlumbingNav guide will help you determine if you have a problem with your thermocouple and show you how to clean it if you do.

What's In This Guide?

      Understanding a Water Heater Thermocouple

      A thermocouple is an electrical sensor. Two wires on one end connect to a thermometer on the other end. This item acts as a safety measure by shutting off the gas to the water heater when the pilot light goes out. 

      The thermocouple generates a small electrical current when it comes into contact with heat (the flame from the pilot). When the heat creates this electrical current, this electrical current keeps the gas valve open. 

      When the pilot goes out, the electrical current disappears, causing the gas valve to close. This is designed with your safety in mind. 

      Did you Know How to Clean a Thermocouple Water Heater

      How to Clean Your Water Heater’s Thermocouple

      Here is a simple step-by-step guide on how to clean your gas water heater’s thermocouple by yourself. This can resolve the problem if your pilot light goes out often. 

      First: Gather these supplies:

      • Wrench 
      • Sandpaper 
      • Cloth
      • Screwdriver
      • Owner’s Manual

      ***When picking cleaning supplies, avoid all supplies that contain chemicals. While the cleaner may describe itself as a thermocouple cleanser, chemicals and gas never mix. Stay safe and avoid these types of cleansers. Use a mixture of soap and water instead.

      Step 1: Verify the Thermocouple is the Problem 

      How do you know that your thermocouple needs cleaning? One easy way to determine if the thermocouple is the reason you’re having trouble with your hot water heater is to pay attention to what happens when you light the pilot. 

      If the pilot lights, but it goes out when you let go of the ignition button, the thermocouple is likely to blame. The pilot isn’t heating the thermocouple enough to maintain a strong enough electrical current to keep the gas valve open. 

      If the pilot light won’t ignite at all or it lights for extended periods of time then goes out, the thermocouple is likely not the problem. 

      If you are sure the thermocouple needs a cleaning, continue through the process to clean it. 

      Step 2: Turn Off Gas

      Before working on a hot water heater, the first step always involves turning the gas off. This ensures you will stay safe while you clean the thermocouple. Get into the habit of turning the gas off every time you perform maintenance or repairs on your gas water heater

      Locate the gas control valve on your gas water heater. In most cases, the gas valve sits at the bottom of the unit. Turn the valve 90 degrees to turn the gas off. You also have the option to shut the gas off to the entire house from the outside. 

      Step 3: Detach Burner Assembly 

      To properly access the thermocouple, unscrew the burner plate. At this time, you will need to disconnect the wires attached to the control center. It’s connected in three places- the thermocouple, the main supply tube, and the pilot supply tube.

      The small copper wire is the thermocouple. At this time, you should be able to remove the burner assembly and access the thermocouple. 

      Experts suggest taking a picture before detaching the burner assembly to help you reattach it properly. 

      Step 4: Clean Thermocouple Thoroughly 

      The main problems with the thermocouple include sediment build-up on the thermocouple itself and corrosion at the connections. 

      To clean the sediment buildup, you will use sandpaper. Steel wool can be used if the sandpaper doesn’t seem to be making the desired progress. 

      Use a cloth to remove any corrosion or rust between the control center and power wire and to give the thermocouple a nice wipe down. 

      Clean thoroughly to provide the best results. Once again, avoid using chemical cleaners that can create problems when in contact with the pilot. 

      Step 5: Replace Burner Assembly

      Replace the burner assembly now that the thermocouple is clean. First, reattach the gas supply and the gas supply to the pilot. Next, you will screw the cover back on. You can use the picture you took earlier or use the owner’s manual if that’s easier. Ensure all connections are tight. 

      Step 6: Reignite Pilot and Check Water 

      Reignite the pilot light on your water heater. To do this, you will turn the indicator to “pilot” and press the ignition button. Once the flame ignites, and you have held the button for 30 – 60 seconds, move the indicator to “ON”. 

      Check the water to ensure it runs hot after about 1 – 3 hours, depending on your water heater. If the water heater appears to work again, great. If not, you may need to replace the thermocouple. 

      Step 7: Call a Plumber 

      At PlumbingNav, we want to guide you to complete simple repairs and maintenance yourself. However, at a certain point, you need to know when to step back and let a professional repair what you tried to fix. 

      If your attempts didn’t work and you start to get frustrated, a plumber can solve the problem for you. This is especially called for if gas work is involved. 

      did you know how to clean thermocouple on water heater

      Thermocouple FAQs

      Does My Water Heater Have a Thermocouple?

      Only gas water heaters use a thermocouple. If you have an electric water heater, you will not have a thermocouple.

      Not all gas water heaters use a thermocouple. Some gas water heaters use a mercury sensor. Check your owner manual to learn what system your particular water heater uses. 

      How do I know if my thermocouple is bad on my water heater?

      The first sign of a problematic thermocouple is that the pilot light won’t turn on. However, keep in mind that this does not mean that the pilot light won’t ignite at all. That’s a sign of a different problem (likely a blocked pilot tube). 

      If the light turns on but goes out after you let go of the ignition button, you should suspect a problem with the thermocouple. This is different than a pilot light that blows out.

      Can water damage a thermocouple?

      Yes. However, before replacing the thermocouple after a flood or contact with water, you can try to dry it out. 

      Detach the thermocouple and allow it to dry out. You may also want to try using a hairdryer on a low setting to dry it out. 

      Reach the thermocouple after you allow it to get completely dry. If it still doesn’t work, you will need to replace it. 

      How do you test a water heater thermocouple?

      You can use a multimeter to determine if your thermocouple needs replacement. Set the multimeter to read for “ohms”. Take two leads from the meter and touch them together. They should read “0”. Now, set the meter back to volts. 

      Next, get the thermocouple hot by putting it to an open flame. Once hot, connect the leads of the multimeter to the thermocouple. 

      Your thermocouple should provide a reading between 25 and 30 millimeters. If it registers less than 25 millimeters, you need a new thermocouple. 

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