§1002 · Trap requirements

Why inspectors flag this

A retrofit that relies on a crown-vent S-trap geometry is the canonical 1002 failures; the drafter surfaces the rule so the trap is replaced with a listed drum or P-trap before the inspector walks the site.

As quoted in the code: Each plumbing fixture has its own individual trap that is self-scouring and resists siphonage; the trap is installed as close to the fixture outlets as practical and is the only trap on the fixture — standpipe receptors carry an approved trap, and S-traps, bell traps, and underfloor traps that rely on a crown-vent geometry are prohibited.