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Water Heater Gas Valve Replacement Guide 

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Do you think your Robertshaw or White-Rodgers gas water heater needs its valve replacing?

Are you considering doing the work yourself but don’t know where to start? Then take a breath of relief, as you have come to the right place! 

We know how tricky and confusing the world of gas water heaters and valves can be.

Even establishing that your valve needs replacing is a tricky task and one that leaves many of us stressed and unsure what to do next. 

Well, no more! Today we are here with a complete guide for you. Just keep reading to find out how you can replace your gas valve and everything else you need to know about gas water heaters! 

What Is A Water Heater Gas Valve? 

A water heater gas valve, also known as the control gas valve, is a small device found inside a tankless water heater.

If you have a tank-type heater, then it will be located at the bottom of the tank. The valve’s job is to open and close the gas flow to your pilot or ignition device and the main burner. 

Your gas control valve comes with a built-in safety shut-off device that closes the gas supply when the pilot light is off or if it extinguishes.

A signal is sent from a thermocouple to do this, turning your gas supply off and keeping you safe. 

Now, in some cases, your gas valve or the thermocouple can fail or become damaged, and they will need to be replaced for your heater to continue heating your water.

Don’t worry, we will look at how you can fix this later on! 

Types Of Water Heater Gas Valves 

Now, the gas valve that you have will depend on the gas water heater you have.

Some brands like Bradford White, the American Water Heater Company, and AO Smith use a White-Rodgers and Robertshaw control valve, whereas other brands and manufacturers use Honeywell gas valves.

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You must identify which valve you have to know how to replace or repair it. You can usually find this information in your heaters user manual.

Below we have a list of some of their features to help you identify them quickly. 

White-Rodgers Water Heater Gas Valve 

White-Rodgers water heater gas valves have some features that you can use to identify them. Let’s take a look at a quick list of features now. 

  • Gas valve assembly with thermostat valve, safety valve, and electromagnet 
  • High limit or temperature probe 
  • Inlet and outlet 
  • Pilot tube threaded port 
  • Thermal switch 
  • Thermocouple threaded port 
  • Valve control knob with on and off pilot settings 
  • Water temperature dual and setting indicator

Robertshaw Gas Control Valve 

Robertshaw gas valves have similar features, but with a few differences. Let’s take a look at their features list now. 

  • Control knob with on and off pilot settings 
  • Gas valve with an electromagnet, thermostat valve, and safety valve
  • High limit or temperature probe 
  • Inlet and outlet 
  • Pilot tube threaded port 
  • Reset button 
  • Thermal switch 
  • Thermocouple threaded port 
  • Water temperature dial and setting indicator 

Component Review 

Now let’s take a closer look at the component itself. Some gas valves come with a manifold gas pressure tap. This allows you to measure the pressure on the line that supplies the main burner.

To do this, you remove the plug and attach the gas gauge. You can then check the pressure against the recommended pressure that will be marked on the water heater gas valve

Your pilot light tube and tube from the main burner will be connected to the gas valve, along with the thermocouple which is used as a safety element. It can work without outside electricity or on 24 VAC.

Now that we have covered the basics of the gas valve and the water heater, let’s look briefly at other components on your water tank that you will want to be aware of. 

Temperature Setting Indicator 

Your temperature setting indicator is installed on the front of the gas valve. It allows you to select the temperature for your hot water.

Usually, the temperature will be set by default on the lowest setting of the heater to comply with safety regulations.

On Robertshaw control valves, you will see a ‘hot’ mark which gives a temperature of 120 degrees Fahrenheit and hotter! 

Ignition 

For your pilot light to be lit, there needs to be ignition.

This usually happens when you switch the control knob to the pilot setting or press the reset button on a Robertshaw valve and press the piezo igniter button.

While this is true for modern heaters, some old water heaters might require you to use a match to manually ignite the pilot. 

Thermocouple 

As we mentioned earlier, your thermocouple plays a vital role in your water heater. The flame from your pilot light heats the thermocouple, generating an electric current.

This current, although small, is enough to keep your gas valve open. Once you release the knob, the gas continues to flow to the pilot too.

Thermostat 

Once the pilot light is on and the gas is flowing, incoming cold water will activate your thermostat. This then tells the water heater gas valve to open the burner.

The pilot light will ignite the gas on the main burner, heating the water. The water will continue to heat until it reaches the temperature set.

The thermostat monitors the heat and interrupts the heating process, once the set temperature is reached. 

ECO (Energy Cut Off)

Now, your gas valve will have two metal probes mounted to its back that are inside the tank.

The longer of these two is the ECO, Energy Cut Off switch. The metal rod expands and contracts with the changing temperature of the water. The probe’s job is to act as a temperature high limit. 

If your water gets too hot, then a sensor on the probe will interrupt the electrical current to the valve, disrupting your flow. 

TCO (Thermal Cut Off)

Finally, we have the TCO or Thermal Cut-Off switch. This resettable thermal switch will turn off the gas supply if the temperature gets too high in the combustion chamber. Now, if there is too much pressure here, the control valve can get damaged, leading to gas leaks or an explosion! 

To prevent this, there is a manual shut-off valve in the gas supply line. If you don’t have one, we recommend installing one.

This will ensure that your heater can be serviced easily but also prevent dirt and other debris from entering the control valve.

If your heater does not shut down, then it’s best to turn off the heater manually at the gas valve. 

Now that we have covered the components you need to be aware of, let’s take a look at how you can remove and replace a gas valve. 

How To Remove And Replace A Gas Valve 

When replacing a gas valve, we recommend only using replacement parts that are approved by the manufacturer. This prevents any further damage or compatibility issues down the line.

You must be very careful when working with your gas valve, you don’t want to apply too much force as this can damage the element. 

When replacing your valve, you might need to remove gas piping and some electrical wires. Make sure that you follow the necessary safety precautions at all times.

Below are the steps we suggest you follow to remove and replace a gas valve. Remember, if you are unsure consult a professional who can do the work for you. 

  • Turn off the manual shut-off valve located by your water heater
  • Turn the thermostat to its lowest setting on the control valve. 
  • Next, turn off the electric power to the heater. 
  • Turn your control knob to off. 
  • Here, you might need to drain the water heater following the directions in your manual. 
  • Next, disconnect your pilot tube, piezo, and main tube. 
  • Disconnect your ground joint union and other connections from the control valve. 
  • To finish, remove the entire gas valve. 

Once removed, you can replace it by inserting your new gas valve. You can do this by following the above steps in reverse order once the new valve is in place.

We recommend using some tape or other approved compound on all connections to ensure the work is secure. Before running water or turning the heater on, check for any leaks. 

Final Thoughts 

And there you have it, how you can remove and replace your water heater gas valve!

The work can be a little fiddly at times, but without a guide and the help of online tutorials or user manuals, you are sure to find your way through! Just be sure to make your safety a priority at all times. 

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age

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