Drainage, Waste & VentQuestion 66 of 360
The minimum diameter of a vent pipe must be:
a.Equal to the diameter of the drain it serves
b.Not less than one-half the diameter of the drain served, but never less than 1-1/4 inch
c.Not less than one-third the diameter of the drain served
d.Not less than 2 inches in all cases
Explanation
The CPC requires a vent to be at least one-half the diameter of the drain it serves and never smaller than 1-1/4 inch. Requiring the vent to equal the drain wastes material, one-third is below the code floor, and a flat 2 inch minimum is not what the code specifies for all vents.
Law Reference: 2022 California Plumbing Code (CPC) §904.0Practice all 360 questions free — no signup required.
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