HVAC Gas Valve FAQ

Have you always wondered about boiler or furnace gas valves? Can you identify the signs of gas leaks and how to prevent them? We go through HVAC gas valve FAQs so that you can find all the answers.

Gas Valve FAQS

View the most commonly asked questions about gas valves below. We go into all the details for HVAC systems, but feel free to reach out and inquire about further questions.

What Is A Furnace Gas Valve?

Gas valves are an essential part of HVAC systems. They are built-in safety features that regulate when gas flows through either a furnace or boiler system.

What Are The 3 Classifications Of Gas Valves?

There are three types used in HVAC systems: manual, thermostatic, and pressure-activated. Each type has its advantages and disadvantages. Manual must be opened and closed by hand, while thermostatic and pressure-activated are operated electronically.


Manual gas valves have several advantages. They are less expensive than thermostatic or pressure-activated options and easier to maintain. These valves also provide a more positive gas supply shut-off, which is important for safety.

The main disadvantage is that they require manual operation, requiring a human operator. The process can be risky if not done correctly. Opening and closing can also be challenging, especially in cold weather.


Thermostatic gas valves are operated electronically and are used to control gas flow to HVAC systems. They are designed to maintain a constant temperature. With this flexibility, both residential and commercial applications can use them. Thermostatic gas valves are available in single- and dual-stage configurations and can be used with either natural gas or propane.

Because the valves are electronically operated, they are more reliable and require less maintenance. They also have a built-in safety feature that prevents the system from overheating. Thermostatic gas valves are available in both single and dual-stage configurations and can be used with either natural gas or propane.

With that said, the valves have a few disadvantages:

  1. They are more expensive than manual or pressure-activated gas valves.
  2. They require electricity to operate, so they will not work during a power outage.
  3. Thermostatic gas valves can be less accurate than other valves and may not maintain a constant temperature.


Pressure-activated gas valves are designed to open and close based on the pressure of the gas in the HVAC system and can be used with either natural gas or propane. They are typically used in equipment that requires a high gas flow, such as furnaces and boilers. These components are less likely to be affected by changes in gas pressure.

How Do I Know If My Gas Valve Is Bad?

If you notice any of the following signs, it may mean you need an HVAC technician to repair or replace the device:

-The furnace is not turning on. Check for any clogs in airflow in this case to eliminate other possibilities, as well as any loose wiring.

-There is a gas smell coming from the furnace. If you smell sulfur, turn off the gas supply! It is combustible and thus is prone to explosions.

-The furnace is making strange noises. Have an HVAC technician check this one and maybe schedule a cleaning for the air ducts.

-The furnace is leaking gas. You may smell this; for the same reason, cut off the gas supply and open all the windows.

How Long Do Gas Valves Last?

Gas valves have a lifespan of between 10 and 15 years. Many models are built to last this long, but occasionally a valve will fail prematurely.

Why Do Gas Valves Fail?

Improper installation is one of the most common causes of failure. Excessive heat or vibration can damage the valves, which can cause them to fail prematurely.

Corrosion is also a common cause. Corrosion can occur when the gas valve is exposed to moisture, which can cause the metal to break down and eventually fail.

Mechanical failure is another cause. Gas valves can fail if the components are not working correctly or the exterior suffers physical stress.

Prevent Gas Leaks With Furnace Part Source

HVAC technicians trust Furnace Part Source as their top heating and cooling system components supplier. When you need your furnace repaired, we have the newest HVAC technologies and discontinued and rare series. Our team also has expertise on which parts will work best.

Please contact us today to learn more about helping your boiler or furnace work properly. Let Furnace Part Source reinforce your system’s built-in safety.