: Can a trap arm only run horizontally, or can the same trap arm contain both horizontal and vertical runs before the point where the vent connects? I'm trying to plumb my kithen sink DWV without using an island vent. Although it is not in an island, the sink is against an exterior wall with a window above and I can't run the trap arm through the studs because it would violate the code for boring load bearing studs. So I want to run the trap arm into the exterior wall, down into the crawl space and then over horizontally to pick up a vent in the same exterior wall just to the side of the window. This is new construction. Is what I'm describing permitted? Thank you very much.
Jeff, If you are under the UPC and they are that strict under the UBC then you have no alternative but to use the upc island sink design or the method where you can see the drain in the cabinet. Useing the island sink method will take a lot of room between studs under the window. We have changed from the UPC to the IPC and IPC allows auto vents. Dale's Plumbing Service Inc LMP