Core TradesQuestion 138 of 700
A standard plumbing trap must maintain a liquid seal with a depth in the range of:
a.2 to 4 inches
b.1/2 to 1 inch
c.5 to 7 inches
d.8 to 10 inches
Explanation
A trap seal of 2 to 4 inches blocks sewer gas while resisting evaporation and siphonage. A shallower seal (under 2 inches) can be blown or evaporated away, letting gas into the building. A seal deeper than 4 inches tends to collect solids and self-siphon, and is not standard.
Law Reference: 2025 CA Plumbing Code §1002.0Practice all 700 questions free — no signup required.
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