About this chapter: Chapter 32 regulates the design of fixture traps, methods for preventing evaporation of trap seals in traps, and the required locations for interceptors and separators. The trap seal of a trap is an essential feature of a drainage system to prevent odors from the drainage piping from entering the building. The discharge of various processes such as cooking and laundry create the need for equipment to retain detrimental greases and solids from entering the drainage systems.
Code development reminder: Code change proposals to this chapter will be considered by the IRC—Mechanical/Plumbing Code Development Committee during the 2018 (Group A) Code Development Cycle. See explanation on page iv.
Each plumbing fixture shall be separately trapped by a water seal trap. The vertical distance from the fixture outlet to the trap weir shall not exceed 24 inches (610 mm) and the horizontal distance shall not exceed 30 inches (762 mm) measured from the centerline of the fixture outlet to the centerline of the inlet of the trap. The height of a clothes washer standpipe above a trap shall conform to Section P2706.1.2. Fixtures shall not be double trapped.
- Fixtures that have integral traps.
- A single trap shall be permitted to serve two or three like fixtures limited to kitchen sinks, laundry tubs and lavatories. Such fixtures shall be adjacent to each other and located in the same room with a continuous waste arrangement. The trap shall be installed at the center fixture where three fixtures are installed. Common trapped fixture outlets shall be not more than 30 inches (762 mm) apart.
- Connection of a laundry tray waste line into a standpipe for the automatic clothes-washer drain shall be permitted in accordance with Section P2706.1.2.1.
Trap sizes for plumbing fixtures shall be as indicated in Table P3201.7. Where the tailpiece of a plumbing fixture is larger than that indicated in Table P3201.7, the trap size shall be the same nominal size as the fixture tailpiece. A trap shall not be larger than the drainage pipe into which the trap discharges.
|PLUMBING FIXTURE||TRAP SIZE|
|Bathtub (with or without shower head and/or|
|Clothes washer standpipe||2|
|Dishwasher (on separate trap)||11/2|
|Kitchen sink (one or two traps, with or |
without dishwasher and food waste disposer)
|Laundry tub (one or more compartments)||11/2|
|Shower (based on the total flow rate through|
showerheads and bodysprays)
Flow rate:5.7 gpm and less
More than 5.7 gpm up to 12.3 gpm
More than 12.3 gpm up to 25.8 gpm
More than 25.8 gpm up to 55.6 gpm
For SI: 1 inch = 25.4 mm, 1 gallon per minute = 3.785 L/m.