: I am remodeling a summer cottage and I am putting a stacking type washer/dryer in a closet. The drain will be a 2" with a standpipe/trap before going into the crawl space and to the main. I would like to use a 1-1/2" vent going up into the attic and connect it to a 1-1/2" vent from the shower that goes directly up and out through the roof. The W/D vent will have to run about 15 feet horizontally once in the attic before it ties into the shower vent and this will include a 90 degree elbow to maximize attic space. Is this OK? Is there a code on horizontal vent runs.
Make sure to pitch the vent piping 1/4 inch per foot. I don't have a code book in front of me but I believe the vent should increase to 2" once you connect to the other 1-1/2" vent line. Although doing as you mentioned should be fine.