Where must air admittance valves be installed according to code?

• A. In an accessible area
• B. Behind a finished wall
• C. In the attic
• D. Outside under eaves

Answer: (A)

Air admittance valves let air into the drainage system from the inside of the building when needed, but they are mechanical devices that must be reachable for inspection, testing, and replacement. Installing them in a location that can be easily accessed ensures you can check for signs of failure, wear, or blockage and service the valve without tearing into finished walls. Placing the valve behind a finished wall, in an attic, or outside under the eaves makes maintenance difficult or impossible and can expose the valve to conditions that reduce its reliability, which is why codes require it to be in an accessible area.