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How to Replace a Water Heater Thermocouple | Repair and Replace Guide

Thermocouple or flame sensors devices used to control the flow of gas in gas water heaters. In older heaters with foot indicators, the device commonly referred to as thermocouples. How to Replace a Water Heater Thermocouple; a question faced by everyone whoever is taking care of such stuff.

Thermocouples are part of a pilot burner assembly connected to a gas control valve outside the water heater. This is a simple device that converts the heat from the burning flame into a small current, allowing you to act as a switch to control the gas flow of the gas supply valve.

Simply put, when the thermocouple does not feel the flame, it prevents the gas valve from transporting gas to the burner. As such, it is a key safety element in the water heater system.
Typically, a bad thermocouple is the reason why the heater pilot does not turn on or the burner does not turn on.

While in new devices with electronic ignition, the same device (or almost identical) is called a flame sensor. For our purposes, we call these two thermocouple devices.

  • How do you replace a Honeywell thermocouple?
  • How much does it cost to replace a thermocouple?
  • Are thermocouples universal?
  • How do you know if you have a bad thermocouple?

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Foot light with electronic ignition

The type of ignition system in the water heater will determine how the thermocouple changes.
Two types of ignition (standing pilot or electronic) thermocouple are part of the burner assembly.
For a standing pilot, simply connect the pilot and thermocouple of the burner assembly.
By electronic ignition, the burner set has a pilot, thermocouple and an electronic lighter.

Tip: If you do not know what kind of water heater you have, look for a pilot flame: Water heater Stand Pilot has a small pilot flame to burn at any time.
Using an electronic ignition heater, the pilot flame will light only when the thermostat requires the burner to be lit.

Disconnect control valve

Disconnecting the gas control valve is the first step in maintaining the electronic ignition or standby pilot water heaters:

  • Turn the water heater gas control valve OFF.


  • Close the shut-off valve on the gas supply pipes of the water heater.


  • Remove the exposed burner assembly cover (foot guide) or the burner manifold cover (electronic ignition).


  • Release and remove the thermocouple connections, main burner feed pipes, and pilot feed pipes from the control valve using an adjustable wrench or an opener wrench.
    For electronic ignition heaters, move the cable to the piezoelectric lighter.

Note: If you have an electronic ignition water heater, go to the next slide.
If you have a Stand Pilot water heater, skip slide 7: Stand Pilot Water Heater — Replacement Thermocouple.

Electronics – Ignition Water Heaters – Dismantling Burner Components Collector Cover

The combustion chamber of a water heater with electronic ignition seals, gaskets.
To get into the combustion chamber, you need to remove the collector cover from the burner assembly, which includes the supply pipe of the burner, burner, electronic ignition, pilot and thermocouple.

  • Follow these steps to remove the collector cover:


  • Remove the fasteners that fix the collector cover of the burner assembly.
    Depending on the make and model of your water heater, the panels can be secured with special tamper-proof nuts, screws or fasteners, such as TORX-HEAD #20 screws.


  • Take the burner feed tube and push slightly down to release the manifold, pilot tube, and thermocouple connection.


  • Gently remove the manipulation/burner assembly from the burner combustion chamber.
    Be careful not to damage the internal components.
    If the burner does not move easily, check around the base, there may be additional screws to fix it.


  • If the old gasket is in good condition and you want to reuse, carefully remove it around the collector cover.
    Otherwise, remove the washing machine and plan to buy a replacement.


  • Clean the metal surface between the cover plate and the water heater.

Electronic Ignition Water Heater — Burner Component Collector View

Once removed, the electronic ignition water heater burner assemblies should resemble the equipment shown here.

Electronics – Ignition Water Heaters – Thermocouple Replacement

The replacement thermocouple is as follows:

  • Slowly, pull firmly and rotate the old thermocouple of its mounting bracket.
    It should be easy to get out if you use firm stress.


  • Be sure not to bend or deform the connection between the guide and the thermocouple holder.


  • The old thermocouple is completely removed by pulling the old thermocouple on (inside out) the rubber gasket, or by opening it on the collector cover of the burner assembly.
    If desired, you can cut the old thermocouple to remove it.


  • Bring old thermocouples to a hardware store, home improvement or plumbing to find accurate alternatives.
    If you are replacing the old one, buy a new gasket for the collector cover.


  • Insert the new thermocouple externally into a ring or opening in the collector cover of the burner assembly.


  • Insert the thermocouple into its mounting bracket until it is fully seated or click in place.


  • Place the tip of the thermocouple so that the pilot flame surrounds 3/8 to 1/2 inch from the tip of the thermocouple.


  • Install a new burner manifold cover gasket, or reinstall the old one if it is OK.


  • Place the burner in the combustion chamber and correctly install the device.


  • Reinstall the cover assembly.


  • Do not tighten the screws or fasteners too much.


  • Go to slide 8: Reconnect to the gas control valve to complete the project.

Spare Pilot Water Heater – Replacement Thermocouple

For old water heaters with foot indicators, it is very simple to disassemble and replace the thermocouple:

  • Once the pilot feed pipes, burner feed pipes and thermocouple are disconnected from the gas control valve, simply lift the burner assembly from the bottom of the water heater and remove it.


  • Slowly pull the thermocouple holder firmly and turn the old thermocouple.
    It should be easy to get out if you use firm stress.
    Be careful not to deform any part.


  • Bring old thermocouples to a hardware store, home improvement or plumbing to find accurate alternatives.


  • Insert the new thermocouple into the stand, remove it until it is completely seated or click in place.


  • Place the tip of the thermocouple so that the pilot flame surrounds 3/8 to 1/2 inch from the tip of the thermocouple.


  • Reinsert the burner into the combustion chamber and install the device correctly.


  • Continue to the next slide to learn about the final steps of the project.

Continue below 8.

Reconnect the gas control valve

For electronic and vertical ignition pilot water heaters: After installing a new thermocouple, reconnect the pilot, burner and thermocouple (and electronic ignition device lighter) to the gas control valve as follows:

  • Reconnect the burner feed pipe, pilot supply pipe, and thermocouple to the gas control valve.
    The thermocouple should not exceed the rigidity of the hand more than 1/4 turn.
    The piezoelectric ignition reconnected to an electronic ignition device.


  • Open the shut-off valve on the gas supply line.


  • Turn the gas control valve to the “open” position.
    For vertical pilot units, turn the pilot unit back on according to the manufacturer’s instructions before adjusting the valve to the organizational unit.


  • Set the thermostat of the water heater to the desired temperature.


  • Use soap and aqueous solutions to check the main and pilot supply lines for gas control valves for gas leaks. Spread the accessories with soapy water and look for bubbles that indicate a leak.
    If a leak is found, tighten all gas connections and recheck with soapy water until no leaks are found.

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