Drainage, Waste & VentQuestion 114 of 360
A fixture is 5 feet from its vent, but the trap arm is 1-1/2 inch, which allows only 3 feet 6 inches. The correct fix is to:
a.Add a cleanout at the trap
b.Increase the trap arm to 2 inch, which allows 5 feet
c.Install a deeper-seal trap
d.Slope the arm more steeply
Explanation
Increasing the trap arm to 2 inch raises the allowable developed length to 5 feet, satisfying the trap-to-vent distance. Adding a cleanout or a deeper trap does not change the maximum trap-arm length. Increasing the slope beyond limits would drop the vent below the trap weir and promote siphonage.
Law Reference: 2022 California Plumbing Code (CPC) §1002.2Practice all 360 questions free — no signup required.
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