What is a key purpose of a trap in plumbing?

A trap is a crucial component in plumbing systems, primarily designed to prevent harmful gases from entering the building. It does this by holding a small amount of water in its curved section, creating a barrier that blocks sewer gases from traveling back up through the plumbing system into living spaces. This water seal is essential for maintaining indoor air quality and ensuring a safe and healthy environment.

While traps may indirectly influence water flow and usage, or even assist in fixture installation by providing a connection point, their primary and most important function focuses on safety and health by preventing the ingress of noxious gases. Recognizing this will help in understanding both the design of plumbing systems and the rationale behind local plumbing codes that mandate the use of traps in various fixtures.