OK, here is some more information. First, I thank you all for such quick replies.
The expansion tank appears to be disconnected from the system. The valve to it is closed. It has always (7 years) been this way.
I opened a drain valve on the expansion tank and some really nasty, dirty water came out. I did not completely drain it, but I might flush it tonight. I have no idea if there is an expansion bladder in the tank. Is there any reason why the expansion tank would be locked out of the system (other than it leaking and the previous owner being too cheap/lazy to repair it)?
I shut off the feed to the automatic (12PSI) feeder and that did not eliminate the leakage, therefore the reducer valve is NOT faulty.
What is a tankless coil? I do not have any idea what references to a “tankless coil” mean. Like I said, I’m not a plumber, but an electrical engineer which means I think I know everything, but I don’t.
The Aqua-stat was replaced last year when high voltage fried it. The system worked fine all winter last year. It could be faulty again, but what exactly does it do?
I have checked a few (not all) bleeders and got no air. I will rebleed the entire system to verify as little air as possible is in it. Is there a minimum amount of air required in the system?
A reminder that this is a HOME boiler system. Not steam. It is in a ranch so there are floors above ground level.
Thanks for your help in advance!
[Edited by Dan Szwarc on 23 October 2000]