IPC 303.2

IPC 1002.3

S-traps are prohibited by IPC 1002.3 (Prohibited traps, item 5) and virtually all modern plumbing codes. S-traps are prone to self-siphoning: as water flows down the vertical leg after the trap, it can create enough suction to pull the water seal out of the trap, allowing sewer gases to enter the living space. A P-trap with proper venting must be used instead.

IPC 1003.3.4

A sampling tee or port must be installed on the outlet (downstream) side of the interceptor to allow the municipality or authority to test effluent quality. This is required by most jurisdictions and sewer use ordinances.

IPC 1003.3.5

Garbage disposals (food waste disposers) are generally prohibited from discharging through a grease interceptor. The ground food particles overwhelm the interceptor's capacity and require much more frequent cleaning, reducing effectiveness.

IPC 312.10 / ASSE 5110

Test cocks on backflow preventers must remain accessible for annual field testing by a certified tester. Obstructing or burying test cocks prevents required testing and is a violation of the water purveyor's cross-connection control program.

IPC 424.3 / ASSE 1016

All shower and tub/shower combination valves must be pressure-balancing, thermostatic-mixing, or combination type to prevent scalding. This is a life-safety requirement, especially for children and elderly.

IPC 424.5

Hot water must be connected to the left side of the valve (when facing the valve from inside the shower). This is a universal plumbing convention and code requirement to prevent scalding confusion.