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

The primary purpose of a P-trap in plumbing is to prevent sewer gases from entering the building. The P-trap is designed with a U-shaped bend that holds a small amount of water, effectively creating a barrier between the living space and the sewer system. This water seal prevents gases that may be present in the sewer lines, such as methane and hydrogen sulfide, from flowing back into the building, which can pose health risks and unpleasant odors.

By maintaining this water seal, the P-trap ensures that the plumbing system operates safely and efficiently. It is an essential component in drain systems, found beneath sinks, bathtubs, and other fixtures. The design of the P-trap, allowing for some water to remain constantly in the bend, is what makes it an effective solution for protecting indoor air quality.

For context, enhancing water flow, storing water for emergencies, or facilitating drainage of excess water are functions not associated with the P-trap. These tasks are typically handled by other plumbing components such as pipes, reservoirs, and drainage systems.