Design & SizingQuestion 9 of 110
A horizontal fixture branch carries 30 DFU. The sizing table lists these branch capacities: 2 in = 6 DFU, 3 in = 20 DFU, 4 in = 160 DFU. Two of the fixtures are water closets. What is the minimum pipe size for the branch?
a.4 in
b.2 in
c.2-1/2 in
d.6 in
Explanation
The 30 DFU load exceeds the 20 DFU capacity of a 3 in branch, so the table already forces the next size, 4 in (160 DFU). The presence of water closets independently forbids anything smaller than 3 in, but here the load alone requires 4 in. Always pick the smallest size whose capacity equals or exceeds the load.
Law Reference: IPC §710.1Practice all 110 questions free — no signup required.
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