Main Vent Question

Sorry that this may be a bit long but anyway: I need to replace the main vent down in my basement. Hopefully I can explain this right - coming up off the furnace is, let's say, a 3 inch iron pipe that after coming up off the furnace does a 90 degree angle and begins the Hartford Loop (I believe). Anyway, after going about 3/4 of the way around the piping drops about 6 inches. At the drop is a 90 degree elbow and this is where the main vent is located. After it drops the piping becomes 2 inch piping. But back to this main vent location. Since it's on the elbow that's dropping down the vent hole is not on the top of the piping but on the side. This might sound confusing but what this does is this - I ordered a Gorton valve #2 air eliminator. This valve is not angled so it seems that it should go into the top of a pipe and stick straight up. The way my vent is will make it stick, let's say, parallel (sp?) to the ceiling. I don't know if that matters or not. On another note, the main vent hole is just about 1/2 inch. The Gorton #2 says 1/2 inch but really is bigger than that b/c their just measuring the hole in the vent and not including the threads which makes it about 3/4 inch. So I took the old one off (which, by the way, comes out of the hole and makes a 90 degree angle and goes straight up)and it says # 3 on it. I couldn't tell what brand as it may be 50 years old but I can see the # 3. Sorry, I can't include pics but I hope someone gets this.

 

I'm not clear about what you are trying to do but, I'll take a stab at it. The valve that you ordered should tell you the proper position you must place it in. If you have a thermostactic float valve, or float valve, they have to be installed in a vertical position, a plain thermostatic you can probably get away with a horizontal hook-up. You should have taking the original valve out and have the supply house match it. All plumbing and heating pipe is measured by the inside not the outside. I hope this does some good.