Furnace Gas Valve Leaking: What You Need to Know and How to Fix It

Furnace Gas Valve Leaking: A furnace gas valve is a critical component of your heating system that regulates the flow and pressure of gas to the burner. This ensures the safety and efficiency of the combustion process. However, a gas valve leak can cause severe issues for your furnace and home, making it a potentially dangerous situation. It is essential to identify the signs of a leak and know how to respond to ensure the safety of your family and home. 

This post will explain the causes of a gas valve leak, how to fix it, and the symptoms of a faulty valve.

The furnace gas valve leaks when the furnace’s gas valve fails to seal properly, resulting in gas escaping from the valve. This issue can occur for different reasons, such as wear and tear, corrosion, dirt, debris, or damage. Leaking furnace gas valves can be dangerous, leading to gas leaks, explosions, fires, or carbon monoxide poisoning. You can also view our detailed guide on Gas Valves vs Water Valves.

In addition, furnace gas valve leakage can also impact the furnace’s performance and efficiency, as it can reduce the gas pressure and flow to the burner, leading to incomplete combustion, low heat output, or furnace cycling.

Replacing a defective gas valve is crucial to fix gas leakage problems. However, it’s a job that should be left to the professionals. Replacing a furnace gas valve costs between $200 and $800, including the gas valve, which ranges from $75 to $600, and labor costs from $125 to $500.

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However, before you replace the furnace gas valve, you should first confirm that the gas valve is indeed leaking and not something else. You can do this by following these steps:

  • Turn off the gas supply to the furnace and disconnect the power cord.


  • Check the furnace gas valve for damage, corrosion, or dirt. Clean with a soft cloth and mild detergent. Don’t use abrasive or flammable materials.


  • Reconnect the power cord and turn on the gas supply to the furnace.


  • Check for gas leaks around the valve using a gas leak detector or soapy water. Bubbles or hissing sounds indicate a leak, which requires valve replacement. If there are no signs of a leak, the problem may be elsewhere.

Furnace gas valve leaking can have various causes, such as:

  • Wear and tear: The constant opening and closing of the valve, high temperatures and pressures, and long periods of use can cause the valve to lose its seal, which leads to gas leakage.
  • Corrosion: Moisture, oxygen, or chemicals in the gas can cause the furnace gas valve to corrode, resulting in rust and cracks. These gaps will allow gas to escape, causing a leak.

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  • Dirt and debris: Dirt, dust, lint, or insects can enter the valve through the gas line or air intake, causing the furnace gas valve to clog. This can prevent the valve from closing correctly and lead to leaks.
  • Damage: Physical impact, vibration, or overheating can cause the furnace gas valve to break or warp, leading to leaks.

Symptoms of a Bad Gas Valve on Furnace

A bad gas valve in the furnace can cause several symptoms, including:

A gas leak from your furnace is a clear and dangerous symptom of a faulty gas valve. Signs of a gas leak include a strong gas smell, hissing, or visible gas flames near the valve. Furnace gas valve leaking causes headaches, nausea, dizziness, fatigue, and carbon monoxide poisoning. If you suspect a gas leak, turn off the gas supply, evacuate immediately, and contact the gas company or fire department. A damaged gas valve can cause a safety hazard as fuel can leak into the air, leading to potential fires. In case of a gas leak, evacuate immediately and seek the assistance of a furnace repair expert.

One of the signs of a defective gas valve in a furnace is a complete shutdown of the system. This happens when the valve fails to open or close, preventing gas from reaching the burner. As a result, your furnace stops working, leaving you without heat. Check the gas valve for leaks or blockages if your furnace shuts down unexpectedly. However, a complete shutdown of the furnace can be caused by many other problems, so it’s best to call a professional HVAC technician to diagnose and fix the issue.

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A furnace that is flooded is a possible symptom of a faulty gas valve on the furnace, although it is less common. This occurs when the gas valve fails to close correctly, allowing excessive gas to enter the burner. This can lead to a build-up of gas in the furnace, which may cause the furnace to ignite violently, resulting in a loud boom or a flash of fire. This can cause damage to both the furnace and the surrounding area. If your furnace makes a loud noise or a flash of fire, you should immediately turn off the gas supply to the furnace and call a professional furnace technician.

If your gas furnace is submerged in water, its valve may malfunction. Expert HVAC technicians highly recommend that you replace the component in such a situation, even if you believe that too much water did not seep in or the gas furnace was only partially submerged. This is a crucial safety rule that you should never overlook!

When your furnace stops producing heat, it may be due to a faulty gas valve. This issue can happen when the valve fails to open properly, causing a blockage that prevents gas from reaching the burner. This can cause your furnace to run but not generate any heat. Additionally, it can cause your furnace to switch on and off frequently, increasing your energy bills. If you are experiencing this issue, you should check the gas valve for leaks or blockages.

When your furnace’s gas valve malfunctions, it can hinder combustion. If the valve doesn’t let enough gas into the combustion chamber, your furnace won’t be able to transfer heat through the heat exchanger, air handler, and your home. As a result, you will receive room-temperature air flowing through your home’s vents.

Constant furnace cycling is another symptom of a bad gas valve on the furnace. It occurs when the gas valve fails to regulate the gas pressure and flow properly, causing the gas to fluctuate in the burner. This causes the furnace to cycle on and off constantly, trying to maintain the desired temperature. It can also cause the furnace to overheat, wear out, or break down. If your furnace cycles on and off constantly, check the gas valve and see if it is leaking or stuck.

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In some instances, a heating system may be located near water pipes or washing machine components. Rust and erosion caused by burst pipes or excess moisture can lead to damage and inconsistent operation.

A multimeter is a device that can measure an electrical circuit’s voltage, current, or resistance. You can use a multimeter to check the furnace gas valve and see if it works properly. To do this, you will need to follow these steps:

  • Turn off the gas supply to the furnace and disconnect the power cord.
  • Locate the furnace gas valve and remove the wires that connect it to the furnace. You may need to use a screwdriver or a wrench to do this.
  • Set the multimeter to resistance mode to test the gas valve and touch the probes to the valve terminals. If the reading is zero or infinite, replace the valve. If it falls within the range specified by the manufacturer, the valve works fine, and the issue may be elsewhere.




Your furnace’s gas valve is critical to ensure safe and efficient combustion. It prevents severe hazards like gas leaks, explosions, fires, or carbon monoxide poisoning and optimizes your furnace’s performance and efficiency. It can also adjust the temperature and flame size for convenience. To ensure your gas valve works effectively, have it inspected and maintained regularly by a professional HVAC technician.

In conclusion, furnace gas valve leaking causes serious safety risks such as gas leaks and fires. Identifying the causes, such as wear, corrosion, or debris. Preliminary checks should involve cleaning and inspection; professional replacement is highly recommended. Symptoms such as gas leaks, shutdowns, lack of heat, or constant cycling demand immediate attention. Regular HVAC inspections ensure ongoing safety and efficiency. Prioritizing prompt action is essential to safeguard your home and loved ones from potential hazards.


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