How to Purge Air

Hot water radiators can be purged of air for greater efficiency and warmth.

Air bleeder valves are installed on hot water heating systems to purge unwanted air from radiators. Without purging, the volume of air may become so great the heating system will not be able to provide heat to the radiator spaces occupied by air. Purging the air from a home hot water radiator system releases the trapped air and restores the system circulation. You can effectively purge accumulated air in your system with the proper tools, some time and a little patience.

Things You'll Need

• Radiator key
• Needle-nose pliers
• Plastic cup
• Paper towels

Instructions

1. Turn the heating system thermostat to a temperature higher than usual to allow the heating system boiler to operate for 10 to 15 minutes. This will ensure the system is warm and up to its normal operating pressure.

2. Check each radiator for warmth. If one or more are cold, check the cold radiator's water inlet valve at the bottom of the radiator to ensure it is in the "Open" position. To fully open a closed inlet valve, turn the valve handle counterclockwise by hand until it stops.

3. Insert a radiator key into the bleeder valve at the top of the radiator. The valve can be identified by its recessed square-driveshaft. If you can not locate a radiator key, a pair of needle-nose pliers are a viable substitute.

4. Turn the valve shaft counterclockwise to open while holding a cup under the valve spigot. If air is in the radiator, the hissing sound of escaping air will be heard

5. Continue to hold the cup beneath the spigot. When the hissing stops, the air has been purged from the radiator and water will begin to run out from the valve spigot. As soon as this occurs, close the valve.

6. Repeat Steps 2, 3, 4 and 5, as needed, to purge accumulated air from other radiators. Clean up any spills or drips with paper towels.

Tips & Warnings

• If the upper section of a radiator is not as warm as the lower, it is an indication that there is trapped air inside the radiator.

• Once a radiator is purged of air, expect it to become uniformly warm in one to three minutes.

References

• ELocalPlumbers.com: How to Remove Air from a Heating System
• InspectAPedia: Guide to Air Bleeders for Radiators, Baseboards, Convectors
• USA Plumbing: How to Bleed a Radiator