First off, forgive me if my terminology is off. OK, I had an original "gravity" boiler system. The old expansion tank was way up in the attic. The tank/leftover pipes are higher than any radiator. I'm concerned about the air trapped in these pipes without a radiator to bleed. Do I simply insert an air release valve like the Taco slimeline hy-vent model below. Please see diagrams. OLD SETUP NEW SETUP?? http://http://www.pexsupply.com/product_dtl.asp?pID=4551&cID=305&brand=Taco thanks!!