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Can an air admittance valve (AAV or Studor) be installed horizontally?
Tuesday, February 1, 2022
Manufacturers specify that an air admittance valve be installed within 15º of vertical. So the sideways installation shown above is not acceptable, and it will not function properly in that position. The International Residential Code (IRC) and Residential Edition of the Florida Building Code (FBC) further specify that an air admittance valve be located a minimum of 4-inches above the horizontal branch drain (trap arm) of the fixture being vented (FBC 3114.4).
Also see our articles What is an auto vent, air admittance valve, or check vent? and How many plumbing vents through the roof are required by code? and Is an air admittance valve (AAV) legal by code? and What are the code requirements for plumbing vent terminations?
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