Drainage, Waste & VentQuestion 132 of 360
What is the minimum diameter permitted for a vent pipe, regardless of the fixture it serves?
a.1/2 inch
b.3/4 inch
c.1 inch
d.1-1/4 inches (32 mm)
Explanation
No vent pipe may be smaller than 1-1/4 inches in diameter. In addition, a vent must generally be at least one-half the diameter of the drain it serves. Undersized vents are prone to clogging and cannot relieve pressure fast enough to protect trap seals.
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