### P-Traps & Venting Basics

A **P-trap** holds a small amount of water that seals the drain line, preventing sewer gases from entering your home.

A **vent pipe** allows air into the drainage system to balance pressure and prevent the trap from siphoning dry.

- **Trap seal:** Water barrier against odors and gases
- **Vent purpose:** Equalizes pressure so wastewater flows smoothly
- **Wet venting:** Uses one vent for multiple fixtures in small runs