Design & SizingQuestion 20 of 110
A storm sizing table is published at 4 in/hr. A vertical leader lists a capacity of 4,600 ft^2 of roof at 4 in/hr. If the local design rate is only 2 in/hr, what roof area can that same leader serve?
a.2,300 ft^2
b.4,600 ft^2
c.18,400 ft^2
d.9,200 ft^2
Explanation
Capacity in area is inversely proportional to rainfall rate, so halving the rate from 4 to 2 in/hr doubles the allowable area: 4,600 x (4/2) = 9,200 ft^2. Conductor capacity is fixed in gpm, so a lighter storm lets the same pipe drain more roof. Always adjust table areas to the local rainfall rate.
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