FlyingScot
New Member
Redoing a bathroom with an unusual drain situation for which I am not responsible. The toilet currently sits directly atop a 3” (may be 4”) vertical ABS waste pipe that connects to the main drain under concrete and 3+ feet of dirt. The sink had a trap that drained into its own 2” ( I think) vertical PVC pipe into an older clay pipe through the same concrete and dirt and into the main drain. This pipe is directly underneath the sink not in the wall. The plumbing is in a ground level crawl space about 3ft above the basement floor. Nothing in this bathroom is vented however there is an atmospheric vent approximately 15 ft away that vents the remainder of the fixtures for the house (full bath, kitchen sink, dishwasher, W/D) which happen to all be on the same side of the house. The drain serving the second bathroom was installed and tied into the main drain 50+ years ago before the basement floor was concreted. I need to vent the new fixtures but due to the architecture of the house I cannot vent through the roof or through the wall. It simply cannot be done due to windows and soffits with vents. The toilet is the main issue. I think it will have to be vented on it’s own because it isn’t connected to the sink and I’m unsure if it can be. My municipality allows AAVs in these types of situations but because of the vertical orientation of the drain pipe I’m unclear on how to install it and I cannot for the life of me find any resources that comment on my situation. Can an AAV be installed in one side of a sanitary Y or is it absolutely necessary to install it in a horizontal length of pipe? And could we accomplish this with a San Y, 45 degree elbow and a short length of pipe with the end capped off? I know AAVs are not the best way but for my situation it really is the only way. FTR the toilet and sink functioned perfectly despite the wonky plumbing.