A horizontal branch serves two water closets (3 DFU each), two lavatories (1 DFU each), and two showers (2 DFU each). What is the minimum branch size?

Giải thích

The load is (2 x 3) + (2 x 1) + (2 x 2) = 6 + 2 + 4 = 12 DFU. A 3 inch branch carries up to 20 DFU and allows a maximum of two water closets, so it fits both the 12 DFU load and the two closets. A 2 inch branch (6 DFU) and 1-1/2 inch branch (3 DFU) are undersized, and a 4 inch branch is larger than needed here.