Section 1002.1/Trap Requirements
IPC 1002 covers trap requirements including minimum seal depth, prohibited trap types, and individual trap requirements for each fixture.
Each plumbing fixture must have a trap that maintains a water seal of at least 2 inches and not more than 4 inches. Each fixture must have an individual trap except where code-permitted combinations are used (e.g., a single trap for a set of laundry trays). Traps must be self- cleaning (P-traps). S-traps, bell traps, crown-vented traps, and running traps are prohibited because they are prone to seal loss. Trap arms (the horizontal pipe between the trap and the vent) must not exceed the maximum length from Table 1002.2.
Why this section exists
The trap seal is the only barrier between the sewer system and the building interior. Sewer gases contain methane, hydrogen sulfide, and bacteria that cause illness and create explosion risks. The 2-inch minimum seal depth ensures the water barrier survives minor pressure fluctuations. The 4-inch maximum prevents debris accumulation. Prohibited trap types (S-traps in particular) are prone to self- siphoning, which empties the seal and allows sewer gas to enter.
What plan reviewers look for
Plan reviewers check the plumbing isometric or floor plan for a trap at every fixture. They verify that P-traps are specified, not S-traps. They check the trap arm length from the trap weir to the vent connection against Table 1002.2. They verify that fixtures are not sharing traps unless specifically permitted by the code.
Common violations
Related IPC requirements
Section 903 covers the vent system that protects trap seals. Section 702 covers drainage pipe sizing. Table 1002.2 provides maximum trap arm lengths by pipe diameter. Section 1003 covers interceptors and separators (grease traps, oil separators).