How to Change a Thermocouple on a Hot Water Heater

The rising cost of living is forcing over 90% of the population to be frugal and tighten their belts. From clearing loans, taking kids to a good school, ensuring the lights are always on, the water running and the credit card bills, there is only one luxury you can allow yourself, hot showers and baths. However, a water heater that does not heat might have a faulty thermocouple. How long will you endure the cold showers? To you, who is feeling the pinch of the rising cost of living, it is not better to fix it yourself and learn a new skill in the process.

What is a Thermocouple?

When you note that the pilot lights will not stay lit, your thermocouple will require changing. It looks like a short tube running from the pilot to the gas controller. However, it is a device consisting of two metals of different materials joined to form a junction on one end. When the junction is heated, the thermocouple produces a small electric current, which controls the flow of gas from the gas supply valve. If the flame is out, the thermocouple will prevent the valve from delivering gas to the burner.

A Defective Thermocouple

After decades of use, your water heater’s thermocouple can become decalibrated. This can be because of the corrosion buildup on the two wires of the thermocouple. Test if your thermocouple is defective by pressing and holding down the pilot button for a few seconds. Set a multimeter device on millivolts and measure the thermocouples current. Connect one probe of the device to the gas valve and the other to the copper sheath on the thermocouple to measure the current. A working thermocouple will produce an average of 25 to 35 millivolts when the burner unit is burning with a soft blue flame. You will need to replace your thermocouple if you find lower readings.

Thermocouples are universal, and the parts include universal adapter fittings compatible with clamp-type, screw-in, or push-in type pilot burners. You will not have a difficult time obtaining the right fit when purchasing a new one. In this guide, we have a systematic process to help you change your thermocouple. You will need a wrench set, pliers, a replacement thermocouple, and an adjustable wrench.

Here is a systematic do-it-yourself process for changing your thermocouple.

1. Shut off the gas controller valve on the water heater before attempting to do the repairs.
2. Use the adjustable wrench to unfasten the three nuts holding the two gas tubes and the thermocouple. You will be capable of sliding out the burning chamber. While you are at this stage, remove any debris from the burner ports and check for water leaks.
3. Carefully detach the thermocouple from the burner unit. Locate it attached to the pilot’s gas supply tube with clips that snap easily into place.
4. Pull out the thermocouple from the pilot assembly with a pair of pliers and take it with your to home appliances store and buy an exact match. It costs about $5 – $10.
5. Attach the end with the two wires into the pilot assembly and re-attach the thermocouple to the gas supply tube with the clips.
6. Re-insert the burner unit and use the adjustable wrench to reconnect the thermocouple lid.
7. Finally, reconnect the pilot’s gas tube to the valve and the gas supply tube to the burner unit.
8. Turn on the gas and the water, and follow the lighting process displayed on your water heater.

In the case, you smell gas, apply soapy water to joints, and inspect for bubbles. This will pinpoint the location of the leak.

Thermocouple Handling

It is important to understand why the thermocouple failed in the first place. You can keep a record depicting the reason why each one failed and the time it took to fail. You ought to implement a regular thermocouple maintenance schedule such as storing thermocouples at room temperatures. Store it in a non-humid area to prevent moisture build up which could lead to corrosion build up on either or both of the metals.


After a few successful tries, you will have the experience of a repairperson, it will no longer be necessary to remove the burner unit to change the thermocouple. This will only apply if you do not mind reaching under the water heater. You will require a powerful flashlight to light your working area to ensure that you position the thermocouple correctly as well as the multimeter probe when taking the voltage readings.

With this guide, you are in a position to get inspiration to fix the simple appliances in your home without the need of calling a professional. You can involve a family member or a friend and you can have the much needed bonding time with money to spare.

Skip to content