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 table below.
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 |
Based on International Residential Code; local codes may vary.
Min. slope of trap arm: 1/4 inch per foot for traps sized 1 1/4 to 2 inches;
1/8 per foot for traps sized 3 to 4 inches.
To learn more about installing plumbing vents, visit the JLC Field Guide.