a HVAC professional that I know measured the temperature drop on the return on the hot water circulator boiler system in my house (older, home was built in late 50's). He said the drop was not enough, indicating sediment/ and or air bubbles in the system. My problem is, he does not service residential boiler, and just check a couple of things to help me out. No one in my area does residential boilers anymore; how can I flush this sytem completely myself? I'm guessing that once I get it back clean again, I can keep it there by learning how to do the blowdown regularly.