We did a install of a 100000btu 96% goodman/amana furnace recently and the flue pipe configuration was a little different in my opinion.
We put a 2" 90 on pointing to the left, it continued 3' and turned up where it was increased to 3" for 2' and made another 90 turn to get out of the house appr 5' horizontal. immediately outside the house we placed a 45 pointing down and glued a reducer on to decrease it back to 2" .
All of this had good fall, but my question is what are the benefits or problems that could come from this setup if any. Is this something to be concerned about, the flue gasses are condensing as they should be and its not trapping water. Just trying to learn right from wrong.