Main Vents

Reference data and engineering information about main vents for piping systems applications.

mainvents

Overview

Engineering reference data for Main Vents 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	—

6 rows

Maximum Drainage Fixture Units (DFU) for Main Vent Pipes. Note: 1) No water closets are permitted on a 1 1/2-inch vent.
Pipe Size(in)	Max. Drainage Fixture Units (DFU)
1 1/4	1
1 1/2	8
2	24
2 1/2	48
3	84
4	256

Source: engineeringtoolbox.com

Important Considerations

At least one vent should terminate through the roof.
Air admittance valves within the building may be permitted (check with local authority).
Terminating vents in a side wall may be permitted (check with local authority).

Interactive Charts

Drain Pipes and Vent Stacks

References

Original Source

Source: engineeringtoolbox.com