Stormwater Drains Capacity

Overview

Engineering reference data for Stormwater Drains Capacity in piping systems.

Key Formulas

Continuity

$A_1 v_1 = A_2 v_2$

Mass conservation in pipe flow.

Pressure Drop

$\Delta P = f \frac{L}{D} \frac{\rho v^2}{2}$

Darcy-Weisbach equation.

Pipe Area

$A = \frac{\pi D^2}{4}$

Cross-sectional area of a pipe.

Variables

Symbol	Description	Unit
$D$	Pipe diameter	m
$v$	Flow velocity	m/s
$\Delta P$	Pressure drop	Pa
$f$	Friction factor	—

Stormwater Conductor Capacities

The following tables provide capacities for horizontal sloped and vertical stormwater and rainwater leaders based on pipe size and slope.

Imperial Units

Metric Units

Pipe Materials and Standards

Building Storm Sewer Pipes

Subsoil Storm Sewer Pipes

Key Design Considerations

• Vertical roof drains provide significantly higher capacity than horizontal sloped pipes for the same pipe size
• Pipe slope directly affects horizontal pipe capacity — steeper slopes yield greater flow rates
• Pipe material selection should comply with applicable ASTM, CSA, or ASME standards for the intended application
• For building storm sewers, a wider range of materials is available compared to subsoil applications

Interactive Charts

References

• Original Source