I have really enjoyed reading the discussions here and have learned a lot. Thanks to everyone for sharing their knowledge, it really helps!
I think I have diagnosed a problem with our system, I just need some guidance in sorting it out.
First the basics:
It's a two pipe system with vents, with a one pipe system sitting on top of it.
It has convectors as well as the traditional standing radiators.
It was coal, then oil, and now gas.
There is a wet return that runs around the basement, and a "new" hundred year old addition to the house that has a dry return that drains into the wet return.
The two pipers that drip straight into the wet return behave themselves, the ones that drip into the dry return do not.
The problem I am currently trying to solve is that the end of the wet return has, likely from the replacing of a boiler long ago, found its way above the "new" boiler's water line. Just the last ten feet or so are above the water line but there is a lot going on in those last few feet. The attached picture shows the end of the return above the red laser I lined up with the top of the water in the sight glass. Is that the right way to do that?
Would installing an inverted "U" of iron pipe fifteen feet or so back from the problem area to raise the water level be the way to go? Am I at least on the right track?
Thanks in advance!