i want to convert a large walk in closet into a laundry room. can i vent the washer drain,a floor drain, and a sink drain to the attic or does it have to go through the roof?
You can run it into the attic, but you must either run it up through the roof individually, or tie it into one of the other vents that already goes through the roof. The fumes can be potentially both toxic and combustable - you don't want that in your attic.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013