Drainage, Waste & VentQuestion 124 of 360
An air admittance valve (AAV) serving an individual fixture must be installed a minimum distance above the horizontal branch drain it serves. What is that minimum?
a.At the same level as the trap weir
b.1 inch above the flood-level rim
c.2 inches above the fixture drain
d.At least 4 inches (102 mm) above the horizontal branch drain
Explanation
An AAV must be installed at least 4 inches above the horizontal branch drain it serves and above the trap weir of the fixture. This keeps the valve out of the wetted flow path so it can admit air freely when negative pressure occurs. AAVs must also remain accessible for replacement.
Law Reference: 2022 California Plumbing Code (CPC) §918.0Practice all 360 questions free — no signup required.
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