Codes & Safety第 113 / 120 题
A building sewer runs 62 ft from the building drain to the connection at the main and is to be graded at 1/4 in per foot. The invert elevation at the upstream end is 100.00 ft. What is the invert elevation at the downstream end?
a.98.71 ft
b.98.45 ft
c.99.35 ft
d.101.29 ft
解析
Total fall is 62 ft x 1/4 in per ft = 15.5 in, and 15.5 in divided by 12 is 1.29 ft, so the downstream invert is 100.00 - 1.29 = 98.71 ft. The value 98.45 uses 3/8 in per ft or rounds the fall to 18.6 in. The value 99.35 halves the fall, as if the grade were 1/8 in per ft, and 101.29 applies the fall in the wrong direction, which would run the sewer uphill toward the main.
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