Storm Water - Example
Task:
Size roof drain/leader and horizontal piping for a roof area of 5000 sf at a rain density of 3.25 inch/hr.
Solution:
1. Sizing roof drain and leader:
Enter 3.25 in the Rainfall Rate box. Enter 5000 in the Area box. The flow will be 169 gpm. From the Pipe Capacity dropdown menu select 7729. The corresponding roof drain and leader size is 5", which is shown under the header, Drain Dia. The safety margin is (7729/5000 - 1 =) 55%.
2. Sizing horizontal drain:
Enter 3.25 in Rainfall Rate box. Enter 5000 in the Area box. The flow will be 169 gpm. From the Slope dropdown menu select a slope, here, 1/8" per foot, or 1.04%. From the Pipe Capacity dropdown menu select 6585. The corresponding drain size is 6", which is shown under the header,Drain Dia. The safety margin is (6585/5000 - 1 =) 32%.