Here a old systom with one pump that use to circulate with pump off, now I add the dhw. tank and he says it wont circulate?/ I have 4 tanksin my systom and the water will move threw them all with pump off and check valve open I dont understand unless there is still air in the systom? With air this would stop it from moveing the water right?? There are no check valves or controles just the pump is on the inlet side of the boiler,hot comes out the top copper pipe in photo. He has about 4 zones on this one pump but it did move water before?If i incress the presure in the systom to say 25lb, will this help get air out the bleeders? And run the pump one zone at a time.