How to Bleed a Furnace in 3 Steps and Ensure Efficient Heating in Your Home

Proper maintenance of your home's heating system is essential to ensure it runs efficiently and effectively. One aspect of maintenance is bleeding your furnace, which helps to maintain its functionality. Let’s walk through how to bleed a furnace, why and when it's necessary, and some step-by-step instructions for both DIY enthusiasts and those considering hiring a professional.

What Does It Mean to Bleed a Furnace?

Bleeding a furnace, also known as "bleeding the lines" or "purging the system," refers to the process of removing trapped air from the heating system. Air can accumulate in the furnace's pipes, causing reduced heating efficiency or even complete HVAC system failure. This may lead to incurring the costs to install a new furnace.

Bleeding the furnace ensures that hot water or air can flow freely through the system, improving its overall performance. 

When to Bleed Your Furnace

If you’re new to bleeding furnaces, it might be confusing to know when it’s time to bleed yours. Here are some times when bleeding a furnace might be a good idea. 

• After maintenance or repairs: Whenever your heating system undergoes maintenance or repairs, air can enter the pipes. Bleeding is necessary to remove this air and restore optimal functionality.

• Cold spots in your home: If you notice uneven heating throughout your home or certain rooms that aren't heating as well as others, it could be due to air buildup or air pockets in your HVAC system.

• Odd noises or vibrations: If your furnace makes gurgling or banging noises, there's likely air trapped in the system. 

• Reduced energy efficiency: Higher energy bills or other signs of reduced heating efficiency can result from air hindering proper water or air circulation.

• Loss of heat: If your furnace isn't producing sufficient heat, air buildup might be the culprit.

Preparing to Bleed Your Furnace

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There are a few preparation and safety steps you should take before diving into the project of bleeding your furnace. Make sure to turn off the furnace before beginning, and allow it to cool down completely. If it’s a gas furnace, shut off the gas supply, as well, as this prevents any potential gas leaks while you work on the system.

Angi Tip

It typically takes between 30 minutes and one hour for a furnace to fully cool off. Don’t attempt to work on your furnace if it’s still hot or even warm, as you could be burned.

Kassidy Barber

Content Editor, Angi

Then, locate your furnace’s bleeder valve. This valve is usually located near the top of the system, often on or near the pump. Place a container or cloth beneath the valve to catch any water that may come out during the process.

How to Bleed a Furnace in 3 Simple Steps

Bleeding a furnace is a simple, three-step process. 

1. Open the bleeder valve: Using a wrench, carefully open the bleeder valve and listen for the hiss of escaping air. Once water starts flowing steadily, close the valve.

2. Check pressure: After bleeding, check the system's pressure gauge and refill if necessary according to the manufacturer's instructions.

3. Restart the furnace: Turn your furnace back on and ensure it's functioning properly after bleeding.

Tips on How to Bleed a Gas Furnace Safely

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Follow these tips to make sure you’re always bleeding your furnace safely. When in doubt, call in a pro to help. 

• Allow ample cooling time: Give the furnace ample time to cool down before attempting to bleed it. Hot components can cause burns, so wait until the system is at a safe temperature to proceed with bleeding.

• Wear protective gear: Put on gloves and safety goggles to protect yourself from any hot water, steam, or debris that might be released during the bleeding process.

• Use the correct tools: Use the appropriate wrench to open the bleeder valve. Ensure it fits snugly to prevent slipping or damaging the valve.

• Open the valve slowly: When opening the valve, do it slowly and steadily. Sudden pressure changes can cause water or air to rush out forcefully, potentially causing damage or injury.

• Prevent water damage: Placing a container or cloth beneath the valve catches any water that might come out during the bleeding process. This helps keep your work area clean and prevents water damage.

• Close the valve slowly and carefully: Once you've bled the furnace and water starts flowing steadily, close it slowly and carefully to avoid sudden pressure changes.

• Check for leaks: After bleeding and closing the valve, inspect the area around the valve for any leaks. If you notice any, address them immediately and consult a professional if necessary.

• Monitor your furnace: After ensuring everything is secure and there are no leaks, you can turn the gas supply back on and restart the furnace. Make sure to monitor its operation to make sure it's functioning correctly.

DIY vs. Hiring a Pro

Bleeding a furnace is a relatively simple task that many people can perform themselves. If you're comfortable with basic tools and follow safety precautions, this could be a cost-effective option. However, if you're unsure about or uncomfortable with the process, or if your furnace requires frequent bleeding, we recommend hiring a furnace maintenance company near you. They have the expertise to handle the task quickly, effectively, and safely.