Does every plumbing fixture need a P-trap?
Yes — each plumbing fixture must be separately trapped by a water-seal trap, with no more than 24 inches vertically from the fixture outlet to the trap (IRC P3201.6).
The IRC requires each plumbing fixture to be served by its own water-seal trap (a P-trap). The vertical distance from the fixture outlet to the trap weir cannot exceed 24 inches (610 mm), which keeps the seal effective.
Fixtures generally cannot be double-trapped, and the trap must hold a liquid seal between 2 and 4 inches deep (IRC P3201.2). That water seal is what blocks sewer gas from entering the home.
A single trap may serve up to three like fixtures — such as a multi-bowl kitchen sink or a set of laundry tubs — within the code's limits.
Related answers
- How far does a toilet have to be from a side wall or vanity? — IRC §P2705.1
- What is the minimum shower size allowed by code? — IRC §P2708.1
- Where does the outlet have to be in a bathroom? — IRC §E3901.6
- How many CFM does a bathroom exhaust fan need? — IRC §M1507.4
- Does glass around a bathtub or shower have to be tempered? — IRC §R308.4.5
- Does a bathroom need a window, or is an exhaust fan enough? — IRC §R303.3
- When does a water heater need a drain pan, and what size is the drain? — IRC §P2801.6
- Does a water heater need a temperature and pressure relief valve? — IRC §P2804
Need this scoped to your jurisdiction?
Adopted edition and local amendments vary by city and county. Ask Donnie checks your jurisdiction and cites the exact adopted section.
Ask Donnie →General information based on the International Residential Code (a model code). This is AI assistance to verify — not legal advice. Confirm the adopted edition and any local amendments with your local building department (AHJ) and a licensed professional before you build.