Installing a water heater thermocouple involves two steps. First you need to remove the thermocouple and Second you have to install the new one.

Not sure if this is your problem? See the article 'Troubleshooting Gas Water Heater Problems' for a complete listing and discussion of issues and the solutions.

Purchasing a Thermocouple

Before you begin, you should purchase a replacement thermocouple.You can buy generic thermocouples that will work on most gas water heaters. However, they cannot be cut, so you want to get one that is close to the length of the one you have.

See the article 'Purchasing a Water Heater Thermocouple' for information on what you need to watch out for when buying this part.

Removing the Old Thermocouple

Before you start, turn the dial on the gas valve to off. Then turn the gas valve at the gas line to off. Turn it so that it is perpendicular to the pipe.

The thermocouple is attached to the water heater at two locations. The first location is at the underside of the gas valve. The thermocouple looks like a bare copper wire with a fitting on the end. You will need an open end wrench or an adjustable wrench to loosen the fitting.

You will have a cover plate that has to be removed to see the other end of the thermocouple. The outer cover place usually just snaps into slots on the sides of the opening. Squeeze the cover plate to get the tabs out of the slots.

There may be another cover plate with a small window in it that will also need to be removed. This one will have some screws that need to be removed.

Once you have the inner plate removed you should be able to follow the thermocouple to the clip that holds the pilot light. If you can get to it effectively, there may be a retaining clip that holds the thermocouple in place. If there is, use a screwdriver to release the clip and pull the end of the thermocouple out.

If you cannot pull the thermocouple out, you will need to remove the entire burner assembly. This sounds harder than it is. See the article 'Removing a Gas Water Heater Burner Assembly' for instructions on what to do.

Installing the New Thermocouple

Use the old thermocouple as a guide for bending the new one. Use a tubing bender and try to avoid kinking it. When you are satisfied with the configuration you can insert the thermocouple into the retainer at the pilot light assembly. It should seat firmly into place. A click or snap is a good sign that is seated properly.

Put the burner assembly back into the chamber. If there is an alignment clip or seat make sure you get it back in the proper spot. Hook up the gas pipe, pilot light pipe and thermocouple to the gas valve. Make sure the fittings are tight.

Depending on the style of hot water heater that you have you may want to light the pilot light at this point. Your water heater should have a set of instructions on it for lighting the pilot light. Follow those instructions. Generally, you want to turn the gas valve to off. Then turn the gas back on. Have a long barbecue lighter ready and then turn the gas valve to pilot. Light the pilot with the lighter.

See the article 'How To Light a Water Heater Pilot Light' for additional instructions. Pilot lights can be a little fickle. When you don't get them lit in time the gas valve will shut off. Then you have a waiting period before you can try again.

For a water heater that has an igniter, you will want to replace the chamber cover and screw it in place. Follow the instructions on your unit to light the pilot. See the article 'Using an Igniter to Light a Water Heater' for instructions on using this type of system.

With the pilot lit you want to replace any covers that are still off. Turn the gas valve to on and the burner should fire up.

Summary

Replacing a gas water heater thermocouple is not too big of a job. Getting the right one was probably the worst part. Actually it was not that bad, they have generic ones that fit most water heaters. Unhooking the fittings getting the burner assembly free was most of the rest of the work.

We hope that you were successful with this project. More importantly, we hope everyone is able to take showers, bath's or do laundry as desired. Will you continue in your home repair career? We hope so.

Purchasing a water heater thermocouple is going to involve a trip to the home supply store or some time on the internet. You have two choices when trying to purchase a thermocouple. One would be to find an original equipment part (OEM). The Second option (the likely option) would be to find a universal thermocouple that will fit your water heater.

Not sure if you need a new thermocouple? See the article 'Troubleshooting Gas Water Heaters' for more information and a coplete listing of all of the gas water heater topics. After you obtain a new thermocouple you will need to install it. See the articles 'Removing a Thermocouple Assembly' and 'Installing a New Thermocouple' for information and instructions.

The information below will help you to determine what information you need to purchase a new thermocouple that will work for your water heater.

Thermocouple or Thermopile Description

Simply put, the thermocouple or thermopile as they are sometimes called is a temperature sensor. For safety reasons, the gas valve will not allow gas to go to the manifold unless there is a flame at the pilot to ignite the gas.

A thermocouple uses two types of metal to create an electrical current that the gas valve can sense. If the electrical current is transmitted, it means that the end of the thermocouple is hot and there is a flame. Simple right? Don't go looking farther than this for an explanation, this stuff can get pretty techinical.

In practice, the thermocouple looks like a copper wire with a thick section that has a sensor end and an end with a fitting that goes into the gas valve. From an operational perspective the thermocouples for a water heater are all pretty much the same. However, there are two variables, the length and the fittings used to install them, see below.

A failing thermocouple will not send the correct electrical impulse and the gas valve will not release any gas. When this happens, you do not have hot water.

Thermocouple Part Numbers

Hunting up part numbers for water heaters can be a daunting task. First there are so many brands and models out there. Some of the better brands have websites that let you look up information, but as a rule, these websites are not do it yourself friendly. When it comes to specific information that is needed to make a repair, they are very vague.

You may think that looking in your manual and finding a part number is all that will be needed to solve your problem. Find the part number and order a replacemnet. The trouble is that most manuals do not list the individual part numbers for the thermocouple.

Instead, the parts diagram will show the entire manifold as a part. Replacing the whole manifold is an option, but why would you spend the extra money when all you need is the thermocouple or thermopile that costs less than ten dollars?

Some manufacturers do have 'name brand' thermocouples available. They may provide a manufacture date range or model range for which water heaters they can be used on. These will cost more as a rule and can be a reasonable option.

Universal Thermocouples

Universal thermocouples, as the name implies work on most water heaters. They are available online and in home supply stores for a reasonable cost. The length and the thread type are the two concerns when purchasing one.

Thermocouple Length

You are going to want to take the old thermocouple with you to get a replacement. A couple of things to watch for. You want to get one that is about the same length as the one you have. They are sold in in 6" increments for the shorter lengths, 18", 24", 30" and so on. For a water heater, 18" and 24" are common, although longer ones are possible.

Remove the old thermocouple and measure it to see what length you need. Try to get as close as you can to the original. You cannot cut them, bend or kink them, but you can coil them if needed. The length of does not affect how they work.

You may wind up with a thermocouple that is longer than the one you have. You can add a loop or two the make it work.

Thermocouple Thread Types

Left Hand or Right Hand Threads

Many gas valves have a left handed thread where the fitting for the thermocouple goes. You need to make sure which thread pattern you have before you order the new thermocouple. Don't plan on trying to make one work that is the wrong thread.

They make and adapters that will allow you to use a standard thermocouple on either a left hand or right hand fitting. A plumbing supply store should have the adapters available.

Adapter Kits

Most 'Universal' thermocouples include adapter kits along with the thermocouple. This is the best choice in most situation. The package will contain a few different fittings that can adapt to either left hand or right hand thread. Usually, thay also include a couple of different retaining clips for the sensor end of the device.

Thermocouple Cost

You can find 'universal' thermocouples on line for under ten dollars. Most of them include an adapter kit that allows you to install it on most water heaters.

You can pay upwards of fifty dollars for a 'name brand' thermocouple. These will not have adapter kits, so you need to make sure you are getting the right one for the make and model of the water heater you have.

Summary

Thermocouples are an inexpensive but important part on a water heater. If you have time, you can order them online. Keeping a spare handy is not a bad idea. You can also find 'Universal' replacement thermocouples at home supply stores.

With your new thermocouple in hand, you will need to install it. See the articles 'Removing a Thermocouple Assembly' and 'Installing a New Thermocouple' for information and instructions for this task.

Removing the gas burner assembly is not too difficult. Remember, turn the gas supply off to the unit before proceeding with any work.

See 'Gas Hot Water Heater Troubleshooting' if this is not your problem. Is it just the pilot light? See the article 'Gas Water Heater Pilot Light' for lighting instructions.

The first thing you need to locate is the gas valve and the burner assembly. They are near the bottom of the tank. The gas valve has the main gas supply connected to it and three other pipes connected at the bottom of it.

The larger tube in the middle is the main gas supply. The smaller tube is the gas supply to the pilot light. The other copper looking wire or tube is the thermocouple

Older water heaters have a cover plate that just snaps on and off. Newer ones may have some screws to remove. The difference will be the electric igniter that is found on newer models.

The main gas supply comes into the side of the gas valve. There should be a vertical gas pipe that tees into it. You will find the shut off valve for the hot water heater on the vertical gas line. Before you do anything, shut off the gas.

When the handle to the valve is perpendicular to the pipe, the gas is off. When it is parallel, the gas is on. Simple right? Look at the picture and make sure the gas is off.

Then using open end or adjustable wrenches you can loosen the connections below the gas valve. First loosen the thermocouple fitting. There are some gas water heater thermocouples that are threaded left hand. When it won't loosen try going the other way.

Next to remove would be the pilot light supply line. This should turn the normal way. Last unhook the main gas supply. Remove the wire that goes to the igniter if you have one for you hot water tank.

At this point the burner assembly should be free. Remove it from the chamber. The thermocouple might be threaded through the tubing for the gas lines. If it is bent in a special way you will want to preserve this to serve as a model for the new one. Pull the thermocouple out of the pilot assembly.

With the burner assembly out of the way it is a good time to do some maintenance. Get a small brush on a long handle the clean the debris up off the bottom of the chamber. Use a vacuum cleaner to suck up the loose material.

Replacing a gas water heater thermocouple provides the ideal circumstances for a clean up and maintenance job. Dirt and debris build up over time that can interfere with the proper functioning of the burner.

Another task you can do when the burner out is to 'Replace the Thermocouple'.

The gas water heater thermocouple is a safety device. It senses when the pilot light is on. When the pilot is not lit the gas valve will not turn the gas on. Make sure the problem is not your 'Water Heater Pilot LIght', before you attempt this repair.

You could be looking at an hour to change it and ten or fifteen dollars for the part. The thermocouple is made of two different metals that are bonded together.

There are (3) key things related to the thermocouple. 'Purchasing a Thermocouple', you can get generic ones that fit most water heaters at a hardware store. 'Removing the Burner Assembly', you will have to take the burner assembly out to change the thermocouple. Installing a Water Heater Themocouple', With the burner assembly removed, installing the thermocouple is fairly easy.

How a Thermocouple Works

A thermocouple is basically a sensor that sends an electronic signal to the gas valve. The interesting thing is that this sensor does not use electricity to work. Instead it uses the heat from the pilot light to generate the electrical impulse that is sent to the gas valve.

The end of the thermocouple is situated in the pilot light. As long as the pilot light is lit the gas valve senses it via the thermocouple. With the pilot light lit the gas valve will let gas go to the burner.

When the thermocouple starts to fail it will send the wrong signals to the gas valve. The gas valve 'thinking' that the pilot light is out will shut off the gas. The burner won't light and the pilot light will go out. The translation of that is 'NO HOT WATER'. This is usually where the complaining starts. See what you need to do to correct this by reading on.

Gas Water Heater Thermocouple - Information

The part is less than $20. It is a little bit of work to replace it. You will probably be looking at $100 to $125 in labor. This is assuming that you don't get talked into a new water heater. A new water heater can run $800 to $1,500 installed, depending on the type.

Repairing a gas water heater thermocouple usually means that it needs to be replaced. You have to unhook the piping from the manifold and shut down the hot water tank. No draining for this repair.

Try the pilot light first. If you have gotten to this article you have probably already tried.

The hot water heater will not work with a bad gas water heater thermocouple. Not getting it back together or getting it installed incorrectly will leave you without hot water. You are also dealing with natural gas. Make sure the gas is turned off before you attempt any repairs. Gas can explode, make sure the valve is in the off position before you unhook anything.

Troubleshooting a Water Heater Thermocouple

The thermoucouple is a simple replaceable part on your hot water heater. If it is not behaving as it should, replacing it is the only option. There are no adjustments or parts that can be repaired or replaced.

If you have a pilot light that will not stay lit or a burner that will not ignite, the thermocouple is the likely culprit.

Purchasing a Thermocouple

There are universal thermocouples that will fit most water heaters, the length is the critical feature. You will need to measure the one that you have to determine what size you need. You can find a complete explanation in the topic, 'How To Purchase a Water Heater Thermocouple'.

Removing the Manifold

For an older water heater, it is likely that you will need to remove the burner assembly to free up the thermocouple before removing. For instructions see the article on 'How To Remove a Water Heater Burner Assembly'.

Installing a Water Heater Thermocouple

Once the old thermocouple is removed and you have a new one in hand, all you have to do is install it. This is discussed in the article 'How To Install a Thermocouple'.