How To Purge Air From Furnace Gas Line? Essential Guide

Rima Chatterjee

Importance of Purging Air from Furnace Gas Line

Purging air from the furnace gas line is an essential task. Do it regularly to ensure the safe and efficient operation of gas appliances like the fireplace, water heater, or stove. Here’s a 3-step guide:

  1. Turn off gas supply – Before purging air, turn off the valve assembly that controls propane or natural gas flow.
  2. Bleed Screw and Pilots – Open the bleeder screw on top of a valve control knob. Use a flashlight to remove air pockets and oxygen, and press down on the pilot button to make sure the pilot lights are lit.
  3. Ignition Test – When air is removed from the natural gas pipeline, hold down on the igniter switch for a few seconds until sparks hit across the pilot valve assembly. This creates an environment of nitrogen or other gases around potential leaks, which will extinguish without oxygen or ignite temperature.

Keep in mind that purging air can be tricky. Consider hiring a professional technician or seeking advice from experts. I faced a similar issue and used JustAnswer instructions. It took me 4 tries and 90 minutes to get my BBQ working again!

To succeed, you’ll need handyman tools and the resilience of a therapist.

How To Purge Air From Furnace Gas Line

Preparations Before Purging Air from Furnace Gas Line

Safety first! Before purging air from your furnace gas line, take the necessary precautions. If needed, seek professional help! Here’s a 5-step guide to help you get started:

  1. Turn off all gas appliances in the house which could affect the gas piping or propane tank.
  2. Hold a bleeder hose connected to the bleed screw of the bleeder valve, and, on the other hand, locate the valve control knob.
  3. If there’s no pilot light on the furnace or appliance, press the igniter button momentarily several times until it sparks. If there’s a pilot light, try turning it off and on again repeatedly while holding down its button for 30 seconds each time.
  4. Tie in a nitrogen pipeline and pressurize to avoid oxygen entering, which may cause explosive mixtures with natural gas/propane. This mixture requires 4% of natural gas/propane in volume to ignite.
  5. Use a manometer/meter to measure pressure changes/drops across valves and pipes while performing the job.

Verify no leaks in any part of the installation system with certified plumbing/HVAC experts. Then, start purging air from the gas lines carefully.

Remember: The inert gas that replaces air is mostly nitrogen. This reduces the risk of an explosion by leaving oxygen out.

Take caution – incorrect procedures can lead to trapped gas mixture pockets. Rely on professionals for such critical procedures. Don’t wait any longer; get it done right away for safe engagements and satisfying results.

How to Purge Air from Furnace Gas Line?

If you want to purge air from a furnace gas line, there are 6 steps to follow:

How To Purge Air From Furnace Gas Line

Take caution when trying this task. Read specific instructions and know what you’re doing. If you’re not sure, hire a professional technician. Remember that each gas appliance must be purged before use, including those connected to a propane tank. Never ignite an appliance before purging its gas lines, it may cause gas leak accidents. Customers report being satisfied after following these instructions! So, I’m ready to light up my furnace and get warmth – or blow it up, we’ll see!

How To Purge Air From Furnace Gas Line

Verifying and Testing the Gas Flow

Verifying and testing your gas flow is essential to guarantee that your gas appliances – like furnaces, water heaters, and stoves – work correctly. Blockages or air pockets in the gas lines and piping can lead to a mix of explosive air and gas, which is a huge hazard if not detected in time. Here’s a 5-step guide to verify and test the gas flow:

  1. Locate the meter: Find your gas meter first. It tracks your natural gas usage in cubic feet (or cubic meters) and measures how much it costs.
  2. Check Pilot Lights: Ensure the pilot light of your appliance is lit.
  3. Turn on the Appliance: Press and hold down the igniter button until you hear a click or spark, then release it. Wait up to 60 seconds for flames to appear, if it works.
  4. Check Ignition: Verify there’s power flowing into its igniter switch when someone turns on an appliance by the shutoff valve control knob. Sparks indicate the pilot assembly or stove burners/propane tank-based systems are lit.
  5. Hold Bleeder Valve Open: Have one person open the bleeder valve with a hose, while another holds down either an igniter button (for propane) or depresses a valve control knob on natural gas piping fixtures.

Nitrogen is often used for purging since it does not interact with other gases in an atmosphere; thus, making it an inert gas. The result should be zero oxygen content in purged pipeline sections unless there’s a leak. If you don’t feel comfortable performing these steps, call a professional.

Additional Information and Important Notes

When dealing with gas lines in your home, remember that gas is highly combustible. So, keep yourself and others safe by following these key points:

  • Turn off all appliances before attempting to purge the gas line.
  • Only use approved methods for repairing, installing, and modifying propane or natural gas systems.
  • If there is an issue with a gas appliance or system, call a professional technician to handle it. Don’t attempt to fix it yourself.

Be aware that natural gas piping contains air pockets which can cause problems if not removed. If you want to put a pilot light in place without professional assistance, make sure to read the instructions for igniter switches or valves.

To purge the gas line effectively and safely, consider these suggestions:

  • Use an approved bleeder valve or another method to remove air from the system systematically.
  • Use nitrogen instead of oxygen, as nitrogen is an inert gas and won’t react with an explosive air-gas mixture.
  • If unsure whether your valve assembly is working correctly, try turning the knob slowly towards ignite position while pressing down on the igniter button. This will result in either a spark at the spark meter or a pilot light appearing.

By following these steps and paying close attention, you will be able to purge any troublesome pockets of air from your furnace’s natural gas line.


Purging air from gas lines issues can be dangerous, and a professional technician is the best way to keep your gas appliances functioning optimally. Don’t put yourself and others at risk, take action today! Don’t risk an explosive atmosphere when purging air from your gas line!

About the author

Debarghya Roy: A heating systems author, Passionate about energy efficiency and sustainability, Sharing insights and empowering readers through informative blog articles.