What is the primary function of a 'trap' in a plumbing system?

The primary function of a trap in a plumbing system is to prevent sewer gases from entering buildings. Traps are curved sections of pipe that hold a small amount of water. This water creates a barrier that blocks gases that can come from the sewer system, thus preventing them from invading the living space. This is crucial for maintaining indoor air quality and ensuring a safe environment for occupants.

In most plumbing fixtures, such as sinks, showers, and toilets, traps are intentionally designed to provide this safeguard. While other options may relate to plumbing systems, they do not represent the fundamental purpose of a trap as effectively as the prevention of sewer gas entry does. For instance, water flowing to the sewer or filtering debris addresses other aspects of plumbing systems but does not capture the vital role of traps in protecting against harmful gases. Similarly, regulating water pressure pertains more to systems controlling the flow and pressure of water, which is distinct from the protective function of traps.