Roof Drain GPM Calculator
Roof drain flow in GPM comes from design rainfall and tributary roof area, then gutters, downspouts and downstream piping must pass the same runoff.
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Runoff flow
Q = i * A * C * F
Gutter capacity
Q = (1 / n) * A * Rh^(2/3) * S^(1/2)
Downspout screen
Q = open area * target velocity
Related pages
- Pipe pressure drop calculator - Darcy-Weisbach loss, head and velocity from flow and pipe ID.
- Pipe size by flow velocity - pick a first-pass pipe ID from flow and target velocity.
- Pump flow and HP calculator - pump displacement, pressure, flow, kW and horsepower.
- Pump NPSH calculator - available suction head and NPSH margin.