Locating Vents

By code, vents must be placed at least two pipe diameters from a fixture trap. In addition, the length of the trap arm is limited to the distances defined in the figure below.

Figure: Max. Distance Between Fixture Traps and Vents

Max. Distance Between Fixture Traps and Vents

Size of Trap (in.) Distance from Trap (ft.)
1 1/4 5
1 1/2 6
2 8
3 12
4 16

Horizontal Vent Runs

A vent must rise at least 6 in. above the fixture flood rim before running horizontally. If necessary, a pair of 45- degree offsets may be used, as shown in the figure below.

Figure: Horizontal Offset
A vent must rise above a fixture’s flood rim before turning horizontally. If an offset is needed below the rim, use one-sixteenth or one-eighth bends. Do not use one-quarter bends.
A vent must rise above a fixture’s flood rim before turning horizontally. If an offset is needed below the rim, use one-sixteenth or one-eighth bends. Do not use one-quarter bends.


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