Hi All, First order of business. I'm looking at redoing the supply and return piping for the radiators in my mom's house. It is an old gravity system with 4" mains. The reason that I have selected to do this is because she is complaining that her gas bill is realy out of control. The house is pretty old but all of the interior work has been redone. New R13 insulation has been replaced on all exterior walls, all windows sealed up, and so forth. So I don't think very large heat loss is the problem. Is the inefficiency in the oversized mains a large part of the problem????

I don't know if anyone remembers me, I had a really long thread on here last year. Now that we're into heating season, I"ve noticed again that I don't have heat on the second floor of my house. I checked the pressure and it was near zero. I do have heat on the first floor and the boiler is in the basement. I drained the expansion tank and it still didn't raise the pressure, so I added fresh water to the system until the pressure came up to about 17 (this was the normal pressure from before). Then I bled the air out of the lines, but when the boiler runs, it still isn't circulating hot air to the second floor. Everything seems to be working properly. Any ideas?