Each plumbing fixture trap, except as otherwise provided in this code, shall be protected against siphonage, backpressure, and air circulation shall be assured throughout the drainage system using a vent pipe installed in accordance with the requirements of this code.
Each fixture trap shall have a protecting vent so located that the developed length of the trap arm from the trap weir to the inner edge of the vent shall be within the distance given in Table 1002.2 but in no case less than two times the diameter of the trap arm.
For SI units: 1 inch = 25.4 mm
|TRAP ARM PIPE DIAMETER (inches)||DISTANCE TRAP TO VENT MINIMUM (inches)||LENGTH MAXIMUM (inches)|
|Exceeding 4||2 x Diameter||120|
- 1 Maintain 1/4 inch per foot slope (20.8 mm/m).
- 2 The developed length between the trap of a water closet or similar fixture (measured from the top of the closet flange to the inner edge of the vent) and its vent shall not exceed 6 feet (1829 mm).
A trap arm shall be permitted to change direction without the use of a cleanout where such change of direction does not exceed 90 degrees (1.57 rad). Horizontal changes in the direction of trap arms shall be in accordance with Section 706.3.
Exception: For trap arms, 3 inches (80 mm) in diameter and larger, the change of direction shall not exceed 135 degrees (2.36 rad) without the use of a cleanout.
The vent pipe opening from soil or waste pipe, except for water closets and similar fixtures, shall not be below the weir of the trap.