Air Admittance Valve
Intro
Air admittance valves allow air in to vent systems, while keeping odors out of the house.
Journal of Light Construction likes it, but article is from 2005 - [1]
Just observe in the picture how much air admittance valves simplify plumbing design.
Note in this picture, bottom floor toilet shares air admittance valve with sink. Valve is by the sink. Washer has its own valve by the washer sink.
Legality
AAVs are approved by the IRC, and most places in the USA allow it. Which ones don't?
From [2] - Proponents of air admittance valves want them added to the UPC code, but they face resistance from those who remain unconvinced. A recent survey among readers of PM Engineer magazine revealed that 74 percent would consider the use of AAVs for venting systems, while 52 percent said they would use AAVs anywhere the code would allow. Currently, AAVs that comply to American Society of Sanitary Engineering (ASSE) 1050, 1051 and NSF Standard 14 are approved in the International Plumbing codes (IPC/IRC). But the Uniform Plumbing Code (UPC) only allows them under Section 301.2, Alternate Materials and Methods--and only when approved by the authority having jurisdiction.
KY, MA, OH - may have problems with approval - [3]
Distances
4" vertically above trap, and 4" horizontally away from trap? [4]
IPC Section 918
- [5]
- Testing -Air admittance valves shall be installed after the DWV testing required by Section 312 - [6]
