Storm Drain Sizing Calculator
Inputs
ASCE: roofs/pavement 0.85–0.95; lawns (flat) 0.10–0.35; cultivated land 0.30–0.50
in/hr
acres
ft/ft
Tab to move between fields
Results
Design Flow (Q)
10 cfs
Selected Pipe Size
18 in
≈ 5 credit cards
Required Diameter17.7 in
Flow Velocity5.94 ft/s
Pipe Capacity10.5 cfs
1
Identify Input Parameters
4 parameters
= Runoff Coefficient (C) = 0.5, Rainfall Intensity = 4, Drainage Area = 5, Pipe Slope = 0.01
= 5 input(s) provided
2
Calculate Design Flow
Design Flow
= 10
= 10
3
Calculate Selected Pipe Size
= 18
= 18
4
Calculate Required Diameter
= 17.7
= 17.7
5
Calculate Flow Velocity
Flow Velocity
= 5.94
= 5.94