Ndis greater than 1; therefore, with one downspout the system would be downspout controlled. With three, it would be controlled by the gutter capacity, or 0.46 ft3/sec. Use three downspouts to take full advantage of gutter capacity.
Step 4—Determine the roof area that can be served based on the following equation:
Step 2—Compute capacity of downspout. Try a
3-inch diameter downspout
_ 7.06 in 2 qd _ 0.010457 x 7.06 x 5.5 _ 0.17 ft3 / sec
Step 3—Determine whether the system is controlled by the gutter capacity or downspout capacity and make adjustments to number of downspouts if desired. By inspection it can be determined that the gutter capacity (0.46 ft3/sec) exceeds the capacity of one downspout (0.17 ft3/sec) Unless a larger downspout or additional downspouts are used, the system capacity would be limited to the capacity of the downspout. Try using multiple down-
This exceeds the roof area to be served; therefore, the gutter dimension selected and the three downspouts with dimensions selected are okay.
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