Drainage, Waste & VentQuestion 80 of 360
Under the CPC, installing two traps in series on a single fixture (double trapping) is:
a.Required for floor drains
b.Allowed if both are vented
c.Allowed for kitchen sinks only
d.Prohibited
Explanation
The CPC prohibits double trapping because the air trapped between two seals blocks flow and causes sluggish, gurgling drainage. Each fixture is served by a single trap. Venting does not make double trapping acceptable, and no fixture type is exempted from this rule.
Law Reference: 2022 California Plumbing Code (CPC) §1002.0Practice all 360 questions free — no signup required.
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