How to Purge Air From Your System Lines

This is generally a problem associated with a new installation.  It doesn’t come up very often because usually a pump can push air out of the lines without any trouble.  In some circumstances air can create a lock in the lines that will prevent circulation and heat transfer. 

There are some simple steps to purge the air from your outdoor wood furnace system lines.  These steps assume you’ve used Hawken installation parts and have the necessary valves in place.

Make sure all the valves are open.  It’s been known to happen that people have a feed valve or a return valve or both closed when they thought they were opened. Also be sure that the pump is connected correctly, on the feed or lower fittings pumping away from the Hawken unit and towards the building to be heated. 

Shut off power to the pump.  At this point there should not be any fire in the firebox.  No fire should be started in the firebox until after water circulation has been confirmed. 

Close the feed valve.  This will prevent water from back feeding through the lines when we do the next step.

Open the In-House Fill valve.  This will force water from your house or building through the return lines pushing air out with it.  The air will be forced into the water jacket of the Hawken unit and will escape through the fill tube. 

After the air has been purged from the system close the fill valve and open the feed valve near the pump.  Turn the pump back on and verify circulation using either a magnetic rotation tester or checking for air bubbles spinning in the spin down filter. 

The pumps run very quietly but water can usually be heard moving through the lines. 

If you need to purge air from the lines of a secondary building or a loop without direct water pressure from an outside source there are some solutions.  One example is to tie your primary and secondary loops together using tees in the back of the furnace.  If you have any further troubles or if you have other questions just let us know.  We’re always here to help.

Posted by Don Squire - Hawken Energy Outdoor Wood Furnaces