Drainage, Waste & VentQuestion 62 of 360
A 4 inch building drain must be installed at a minimum slope of:
a.1/4 inch per foot
b.1/8 inch per foot
c.1/16 inch per foot
d.3/16 inch per foot
Explanation
For drainage pipe 3 inches and larger, the CPC permits a minimum slope of 1/8 inch per foot (about 1 percent). The 1/4 inch per foot minimum applies to pipe 2-1/2 inches and smaller. The 1/16 and 3/16 inch values are not code minimums for a 4 inch drain.
Law Reference: 2022 California Plumbing Code (CPC) §708.1Practice all 360 questions free — no signup required.
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