Any suggestions on how to clear the airblock? On my hydronic heat system I have a drain valve which is at the lowest point in the system. It has a garden hose thread on it. I use a double female, garden hose to garden hose fitting onto a hose with a shut off to connect into the system with water pressure. I barely crack the water hose to put a small amount of pressure into the system, if you had a water pressure gauge in the line it would be under 5psi. Then bleed, bleed, bleed each heater. The water pressure will pressurize the system and water/air will flow from any leak. The bleed screw of course is a leak and being located on top will allow the air to escape. The pump used to circulate water is a centrifugal type pump which puts out very little pressure so it is very hard to bleed with it. Ken (what do you bet my subject line will trigger a "filter" and require moderator approval?) **************A Good Credit Score is 700 or Above. See yours in just 2 easy steps! (http://pr.atwola.com/promoclk/100126575x1220439616x1201372437/aol?redir=http:%2F%2Fwww.freecreditreport.com%2Fpm%2Fdefault.aspx%3Fsc%3D668072%26hmpgID %3D62%26bcd%3DfebemailfooterNO62)