How do I bleed the air out of a forced hot water heating system? I have two zones. Both zones have two garden hose type spickets attached side by side on the pipes near the boiler(oil fired). Each pair of spickets contains one that is opened, and one that is closed. I am assuming I need to attach a hose to the closed spicket and then open it, but what do I do with the other (opened) spicket?