What is the purpose of a P-trap in plumbing?

The primary purpose of a P-trap in plumbing is to create a water seal that effectively prevents sewer gases from entering the living spaces of a building. The design of the P-trap includes a curved section that retains a small amount of water, which serves as a barrier to these gases. This is essential for ensuring indoor air quality and maintaining proper hygiene within the space by preventing unpleasant and potentially harmful odors from seeping in from the sewer system.

While other components of the plumbing system play roles in different aspects—such as securing pipes in place, deterring backflow of sewage, and filtering debris—these functions are not the main roles served by a P-trap. The focus of the P-trap is specifically on its ability to maintain this water seal, making it a critical part of the plumbing system for health and safety reasons.