Water Heater Gas Control Valve

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What Does The Temperature Probe Do

How to Replace a Gas Control Valve on a Gas Water Heater

The long probe is a temperature probe as well, but it functions differently. It works by responding when the water in the tank gets too hot or too cold.

When the water gets hot then cools, a rod within the long probe presses a lever inside the gas valve. It cuts the gas off when the water gets to the temperature you set. Then it turns the gas back on if the water goes below that temperature.

Hiring A Water Heater Repair Service

Before hiring a local plumber for water heater repairs, be sure to:

  • Look for a licensed plumber that has been in business for more than five years.
  • Browse their reviews on HomeGuide and Google.
  • Get at least three estimates to compare.
  • Avoid selecting the lowest quote as quality may suffer.
  • Get a detailed estimate, contract, and warranty in writing before the work begins.
  • Never pay in full upfront. Follow a payment plan and do not make the final payment until fully satisfied.

This Is What The Heat Limit Probe Does

The short probe is a heat limiter that acts as a sort of safety device. It senses if the water in the tank gets too hot. It works with the thermostat and thermocouple as a sensory team. Together the manage the temperature of the water in your tank.

Automatic Shut-off Feature

If the water in your water heater reaches a critical temperature, the gas valve shuts down.

The temperature in your water heater must not reach a critical level. If that happens, it can lead to serious damage to your water heater and the rest of your property. It can also cause grave injuries to users.

The shut-off feature engages if the temperature probe fails to do its job and your water gets too hot.

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Other Gas Control Valve Issues

There are a few other issues that can cause your gas control valve to malfunction. It’s important to note, that you can not repair a gas control valve. If there is a problem, you must replace it.

  • If the control knob does not turn, you need to replace the valve. Never force the knob.
  • If the pilot button becomes stuck and doesn’t pop-up when released, your control valve will need to be replaced. Be sure to turn off the gas to play it safe.

Find a Local Plumber

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If you suspect your gas valve is malfunctioning, the best first step to take is to check for a gas leak. A gas leak is one of the most common problems youll encounter for a multitude of problems including if furnace isnt igniting, isnt heating properly, or you smell gas. To check for a gas leak, create a solution of soapy water and fill a spray bottle with it. Next, spray the gas valve and lines. Watch carefullyif you have a leak, youll see the soap begin to bubble as gas escapes. This is a readily repairable problem if you have the right replacement HVAC parts.

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Different Styles Of Gas Valves

In this pic. you can see the limit and temperature probe.

This gas valve has the pilot button integrated into the control knob.Some valves have separate knobs for the pilot.

The pilot button on the valve is separate from the control knob.

The control knob must be turned to the pilot position before the pilot button can be pressed.

This control valve is on a newer style water heater .Notice its the same type valve as on the older style water heater in the picture above.

This is a newer style water heater with an unusual control valve.

Notice the two white wires coming out of the bottom of the valve.The wires are connected to a roll-out switch. If there is a flash fire in the burner area this switch will shut the burner and pilot light off.

To replace this valve you would need an exact replacement in order to wire up the roll-out switch.

How Does A Gas Control Valve Work

  • Written by Sage C. on Mar 27, 2010To ensure our content is always up-to-date with current information, best practices, and professional advice, articles are routinely reviewed by industry experts with years of hands-on experience.Reviewed by H.R. Helm on Jan 26, 2022

A gas control valve can be found on any appliance that utilizes gas. These valves are vital for the operation and safety of any gas appliance. The valve does exactly what it sounds like, it controls the amount of gas flowing to create a steady flow without allowing any gas to leak.

The most common gas appliance found in US homes is the hot water heater, although the valve serves the same purpose for heating systems and stoves as well. If you need to know the specifics, here is a brief overview detailing how the control valve functions.

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How To Replace Gas Control Valve On Water Heater

Gas water heaters have a gas control valve allowing more or less gas into the unit, increasing the heat that it can produce. This gas valve has a pilot light and thermostat to help the heating process. There can be issues when one of these may be damaged, such as a faulty gas valve, faulty thermostat, or non-functional pilot light.

Water heater problems when the gas control valve is failure may cause include:

  • water is not being heated to the correct temperature
  • a reduced heat from your water
  • water is too hot

Take a look at your water heater tank and inspect for any dirt or debris build-up in the heating chamber. If there is, you will need to flush your water heater.

Other Water Heater Gas Valve Problems

Rheem Water Heater Gas Control Valve

A water heater gas valve cannot be repaired. If a valve malfunctions it must be replaced.

If the pilot button does not pop-up when you release it, cut the gas off and replace the gas valve.

If the control knob will not turn don’t force it. Replace the valve.

If the high limit has shut the gas valve down the valve must be replaced. It will not reset itself. This will only happen if the thermostat has malfunctioned and the water reaches extreme temperatures, in which case the gas control valve would need to be replaced anyway.

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What Is A Gas Control Valve

If your water heater and furnace appliances run on natural gas, you have a gas control valve somewhere in your assembly. Gas valves, also called control valves, are important to ensure the correct operation and safety of your gas appliance. A gas valve works by controlling the pressure and amount of gas flowing into the appliance, creating a steady flow without room for leaks. Although you wont think it, the pressure the gas flows at is important. Too much pressure could cause a fire or even an explosion. Too little pressure will not allow the pilot to ignite. In addition to controlling the flow of gas, the gas valve also controls the pilot light and water temperature within the appliance.

On your furnace, the process goes a little something like this: when your pilot needs to be lit, a button on the valve is pressed and a very small amount of gas is sent to the pilot head. If all goes well, the pilot will light and heat the thermocouple. The thermocouple will then send a small electric current to the gas valve, which will trigger an electromagnet to open the safety valve and allow more gas to flow out towards the pilot. The pilot will then continue to burn as long as gas is supplied.

About Gas Control Valves

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If you have any trouble finding the right part for your home improvement project, just contact a friendly member of our staff. We offer wholesale pricing on Shoemaker, Woodford, Honeywell, and more.

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Water Heater Temperature Control

Water temperatures in a water heater can vary greatly without ever moving the temperature control.In a gas water heater where the thermostat is located in the bottom of the tank, the water at the top of the tank can be 20 to 30 degrees hotter than water in the bottom.

This is caused by short cycling. What this means is that just enough hot water has been used to cause the thermostat to come on. Cold water has been dumped in the bottom of the tank near the thermostat. So, while this water is heating, the temperature in the top of the tank is rising.

If you find your water much hotter at times this is probably the reason and not the water heater gas valve.Ok, with that being said, water heater thermostats can malfunction. If your water is too hot and you can hear the burner running turn the thermostat all the way down. If the burner stays on, turn the gas supply off and replace the gas valve.

If the pilot is lit, you have a tank of cold water, the thermostat turned up and the burner does not fire up, either the burner orifice is clogged or the water heater gas valve is bad.

Remove the burner assembly. The orifice is located at the end of the burner supply line under the burner. Check the burner supply tube also.

How To Replace Your Water Heater Gas Valve

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If your water is getting too hot, the pilot light isn’t functioning, or the heat limiter trips, there’s a good chance that your water heater gas valve isn’t working properly. These are all tell-tale signs that there might be a problem and it’s time to replace the gas valve.

This article will not only give you step-by-step directions on how to replace the gas valve yourself, but also help you troubleshoot to determine if it is the issue. Whether you choose to do the job yourself or , you’ll be armed with the information you need to know to get your water heater back to performing as it should.

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How To Replace A Gas Control Valve


Gas control valve replacement is fairly simple on most water heater models. With the gas turned off, disconnect the lines connected to the gas control valve using an open faced or adjustable wrench. It is important to hold the water heater in place while applying torque to the connectors or you could cause additional damages.

Take the original valve with you to the hardware or gas supply store to get a matching replacement. Reconnect the new valve in reverse order. If you do not detect gas or a rotten egg odor, relight the pilot and verify that the water heater is working properly.

Newer models may have wires connected to the gas control valve. These wires are connected to a thermal fuse in the burner compartment that will turn off the gas to the water heater in the event of a flash fire. If these wires are present, they are important and must be reinstalled when the valve is replaced. Again, contact a professional plumber if you dont feel 100% comfortable with any part of the gas control valve replacement process.


What Does A Water Heater Gas Control Valve Do

The gas inlet connects to the gas control valve, which then, as the name implies, controls the flow of gas to the unit. The gas control valve allows the pilot to be ignited, and the lit pilot heats the thermocouple. Once the water heater thermocouple is heated, it sends a signal to the gas control valve which allows the burner to operate, heating the water in the tank.

Along with the thermocouple and thermostat, there is a another device protruding from the control valve that senses when the water is too hot and shuts the valve down to prevent the tank from reaching a critical heat limit and causing serious damages or injuries.

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Final Thoughts On Water Heater Gas Control Valve Replacement

Putting a new gas control valve on your water heater is a simple four-step process. Although the gas control valve is expensive, you can save on the cost of labor by doing it yourself.

But if you are not comfortable with the idea of working with gas, that is understandable. It can be dangerous, especially if you are not careful. Call a professional. You can expect to pay anywhere from $200 to $750.

Troubleshoot The Heat Limiter And Thermostat

AO Smith Gas Water Heater Gas Valve Assembly Replacement 100111369

You can choose to replace only the heat limiter or thermostat if they are the parts causing problems. But, it might be a better idea to replace the gas control valve. Doing so is only slightly more expensive.

Anytime a heat limiter trips, you have to change it. But replacing the heat limiter alone may not be enough to solve the problem. You can replace it. But a failed heat limiter is almost always a sign that the thermostat and gas control valve has failed as well.

The thermostat in water heaters can fail. Is the water coming from your water heater is scalding hot? Do you hear the burner running? Try lowering the thermostat. Turn it down all the way.

The burner should shut off. If it stays on, you need to shut off the supply of gas to the water heater and put in a new gas valve.

Consider this scenario.

The pilot works. The thermostat is up. But you have a tank of cold water and the burner is not firing.

You may have a clogged burner orifice. Or the gas valve has a problem.

Take out the burner assembly. The orifice is under the burner, at the end of the burner supply line. Also, inspect the burner supply tube.

It is the only way you will know if these parts are responsible for your water heater troubles.

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Troubleshooting Gas Control Valve Issues

If you suspect that there’s a problem with the gas control valve, you’ll want to do some troubleshooting. It’s always possible that the problem isn’t actually the control valve, but rather one of the components, such as the high limit probe, thermostat, pilot light, or even the gas burner. The issue could also be something simple like a clogged sensor or tube.

In fact, it’s more likely that the thermocouple is defective, rather than the gas control valve. If this is the case, the thermocouple can be replaced relatively easily and for far less money.

Honeywell’s Wt9940 Series Gas Control Valve is an excellent valve. Check your water heater’s specifications to make sure it will work on your system.

How A Gas Water Heater Works

Gas water heaters get the cold water through the dip tube and from a cold water supply.

The thermostat probe, which is part of the gas control valve, senses the temperature of the water inside the tank. If the thermostat dial is set to a temperature higher than the temperature of the water, it sends the signal to the gas control valve to open.

Water heaters equipped with the pilot light require you to set the knob to pilot mode, and once activated, it will get an uninterrupted gas supply, no matter if there is a call from the thermostat.

On the other side, the gas valve will open gas to the gas burner only if there is a call for heating.

As the gas flows to the gas burner, it gets lit by the pilot, and then the heating process starts. Part of the pilot light assembly is the thermocouple used to make sure that the flame is still there. If it is not, the unit stops the gas flow and shuts down the unit. The thermocouple is designed to send minimal electrical current to the gas valve and its electromagnet to keep it open.

Once the temperature of hot water reaches the value set on the thermostat, the gas flow stops, so as heating.

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What Are Signs The Gas Valve On A Water Heater Is Bad

Signs of a bad water heater gas valve include:

  • Lack of hot water
  • Water that overheats beyond the set temperature
  • The pilot button doesn’t pop up after pressing
  • The control knob doesn’t turn
  • Gas leakage around the valve connection

Since these are also common signs of other component failures, rule out simpler repairs first. Check the pilot light, ignitor, and thermocouple before assuming the gas valve has failed.

Water Heater Gas Valve

RHEEM AP14270C Water Heater Gas Control Valve (Thermostat)

What Can You Save? – This is not a cheap repair. The part alone could run $80 to $250. The high end is brand named part vs. an after market replacement. There is a fair amount of labor. This could run you another $200 to $250. Then there is the ‘why spend that much on an old water heater’ pitch. You could get talked into an new water heater. Anywhere from $800 to $3,500.

How Hard Could It Be? – Replacing a water heater gas valve involves draining down the tank, unhooking the gas line, unhooking thermocouple and gas lines to the burner and actually changing the valve. A couple of hours of break a sweat work. These repairs will have a Difficulty Level of: A Bit of Work. These repairs require a Skill Level of: Determined Handyman. For and explanation of the terms in this section, see ‘How to Use This Site‘.

What Can Go Wrong? – You are dealing with natural gas. Make sure the gas is turned off and the area is well ventilated. There will be some residual gas in the lines when you take them apart. Also the water in your tank is hot, shut the tank off and run some hot water until it is lukewarm before you try to drain it. Not getting it fixed will leave you without hot water. This will likely generate a significant amount of complaining from the family.

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