Drainage, Waste & VentQuestion 134 of 360
In a cold climate subject to frost closure, a vent through the roof must be enlarged to a minimum of 3 inches. Where must that increase in size be made?
a.6 inches before passing through the roof
b.At least 12 inches (305 mm) inside the building before the vent passes through the roof
c.24 inches above the roof
d.Only at the roof line itself
Explanation
In frost-closure climates, a vent terminal must be at least 3 inches in diameter to resist closing off from frost. The increase from the smaller vent size must be made at least 12 inches inside the building before the pipe penetrates the roof. This keeps the enlarged, warmer section below the freezing zone.
Law Reference: 2022 California Plumbing Code (CPC) §906.0Practice all 360 questions free — no signup required.
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