How to Replace a Water Heater Gas Valve – A Brief Guide

If your water is getting too hot, the pilot light isn’t working, or the heat limiter trips, your water heater gas valve is probably not operating correctly. These are all indicators that there is a problem and that it is time to replace the gas valve.

This article will not only show you how to change the gas valve yourself but also help you troubleshoot to establish whether that is the problem. Whether you choose to handle the task yourself or hire a professional plumber, you’ll be equipped with the knowledge you need to get your water heater back up and running.

How a Gas Control Valve Works

A gas control valve is a safety device that regulates the gas flow to your water heater. It has two parts – a gas control knob that you turn to control the flow of gas and a valve to shut it off and stop the gas flow. Turning the gas control knob one way allows gas to flow into the water heater and allows it to light. Turning it the other way stops the flow of gas, and the water heater goes out. The valve is attached to the gas line, and if the knob accidentally gets turned the wrong way, the valve will be closed, and no gas will be able to flow into the water heater. If this happens, you can turn the gas control knob to the other way, and the valve will open, and gas can flow again.

The gas control valve has a thermocouple built into it that will shut the gas off and cause the pilot to go out if it loses gas pressure to prevent gas from flowing into the water heater if there is a leak or rupture. 

You should also be aware that if you have a gas water heater, you probably have a gas pressure regulator on your house to which the gas line going to your water heater is attached.

How to Replace a Gas Control Valve

Connect the gas valve to the gas tube with Teflon tape or pipe compound. Replace the valve with the previously indicated threaded pipe, but be careful not to overtighten. This might cause the valve to fail and gas to flow. Replace the piezo igniter, manifold tube, pilot tube, thermal switches, and thermocouple, paying close attention to threads. Make sure the combustion chamber is clean and debris-free.

Refill the tank and open the water faucet to allow any air escape. Test the valve for gas leaks by applying foamy, soapy water to the gas connections with a sponge. If it bubbles, it might be a leak that has to be repaired. Re-light the pilot using the instructions for your tank.


A faulty gas control valve can be the cause of various problems with your water heater. The valve will shut off the flow of gas if there are gas leaks or if there is a decrease in gas pressure. This is a safety feature that is built in that will automatically shut off the gas if there is a problem so that a leak doesn’t cause a fire or explosion.

The valve also contains a thermocouple that will shut off the flow of gas if the temperature in the water heater gets too hot. This built-in safety feature will protect you from a scalding hot shower or hot water that could cause a fire if it overheats.

Professor Plumb is a plumbing and drain service in Columbiana, AL, that has been in business for 20 years. We have a team of licensed experts bonded and insured to fix plumbing and gas problems in your home or commercial space. Call us now!

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