: 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, you have to plumb the kit sink according to the code that applies to your area. I have not in my 38 yrs of plumbing never been prohibeted to drill the studs out under the window for the kit sink horizontal trap arm. Do some checking on that. Tell me what code applies to you and i'll send you a drawing. Dale's Plumbing Service LMP