I'm remodeling a bathroom and among other things I need to re-route a furnace vent pipe.
The furnace is on the first floor and the bathroom is on the second. On the second floor the vent pipe comes vertically through the floor and then has a 45 degree elbow close to the ceiling, then straight up into the attic (obviously, through another elbow). The pipe used to be enclosed in a soffit, which I removed.
What I want to accomplish? Ideally, I'd like to re-route the vent pipe as close to the ceiling (or conceal it completely) since due to the 45 degree elbow now it's in the way.
The vent pipe is a double-walled one as required for gas burning appliances.
I did some research on this site and I found that I have to comply w/ two main requirements:
1) keep at least 1" clearance between the vent pipe and combustibles (e.g. studs in the wall/ceiling)
2) If there is a horizontal part of the pipe, its length should not exceed the vertical one
My question is on requirement #2: sounds like I can replace the 45 degrees elbow with a 90 degrees one (and then another one for the vertical into the attic) IF the length of that horizontal section is less than the vertical through the attic (in my case, about 3ft horizontal followed by 4-5ft vertical). I do not account for the vertical part of the vent pipe between the first/second floors. Is this correct? Any problems with having the horizontal section concealed in the ceiling (provided that I keep the 1" clearance)?
Thank you very much in advance for any answers/advice you might have.