Shouldn’t a high efficiency furnace still have a cap at the top of the vent pipe to prevent water from entering. Also it was reduced just before it went through the roof from a 3" down to a 2" pipe. It may be just me but some things seem rotten in Denmark.
Yes they normally place a U-Bend on a vertical riser would have to see the MFG requirements for size reduction in the stack but as a general rule they do not decrease.
Charlie… does it really matter much as it is a condensing furnace and even when placed thru the wall they get wind driven rain.
Plus they are a small diameter.
Agree on the dia though.
rain that falls into this vertical pipe simply travels back to the furnace with all other condinsate and is removed from system.this pipe is pitched back to the furnace.
We typically use a 3 inch vent with U-bend simply because the little 3/4" rubber drain line does not handle the volume of water allowed to enter a 3" vent from the types of tremendously heavy rains we have in this state we call them toad stranglers. Seen many furnaces with the rubber drain line kinked thus adding to the possibility of restriction. Very likely a AHJ rule for this area.