N.Y.C. Admin. Code § PC 911: Section PC 911: Common Vent

911.1 Individual vent as common vent.

An individual vent is permitted to vent two traps or trapped fixtures as a common vent. The traps or trapped fixtures being common vented shall be located on the same floor level.

911.2 Connection at the same level.

Where the fixture drains being common vented connect at the same level, the vent connection shall be at the interconnection of the fixture drains.

Exception:

Where wet vents are permitted by this code, the wet vent connection may be located downstream of the interconnection.

911.3 Connection at different levels.

Where the fixture drains connect at different levels, the vent shall connect as a vertical extension of the vertical drain. The vertical drain pipe connecting the two fixture drains shall be considered the vent for the lower fixture drain, and shall be sized in accordance with

Table 911.3

. The upper fixture shall not be a water closet.

Table 911.3 Common Vent Sizes

Pipe Size (inches)

Maximum Discharge from Upper Fixture Drain (dfu)

1 1/2

1

2

4

2 1/2 to 3

6

For SI: 1 inch = 25.4 mm.