by Jerry Peck - Codeman on Wed Aug 18, 2021 3:56 pm
Floor drain trap primer.
Whenever water is used at that sink, some of the water goes out and down the piping, which most likely goes to a floor drain, and helps keep the floor drain primed and not evaporate dry.
Was there a floor drain in that room, or maybe in the room on the other side of the wall?
Is that an AAV, or is it a mechanical vent? AAVs are permitted, mechanical vents are not (except in manufactured homes and RVs).
Jerry Peck - CodeMan
AskCodeMan.com
Construction Litigation Consultant - Retired
Construction and Code Consultant - Semi Retired