What is the purpose of a trap in plumbing systems?

A trap in plumbing systems serves the critical function of preventing the escape of sewer gases into a building. Traps are designed to hold a certain amount of water, creating a seal that blocks the passage of gases from the drainage system into occupied spaces. This water barrier is crucial for maintaining indoor air quality and ensuring the safety and comfort of occupants by eliminating unpleasant odors and harmful gases that may contain pathogens.

Understanding the various roles of plumbing components highlights why other options do not align with the primary purpose of a trap. For instance, while air venting is important for maintaining drainage efficiency and preventing suction, it is achieved through different venting systems, not traps, which specifically address gas escape. Similarly, measuring the flow of water in pipes is a task performed by flow meters, not traps. Traps do not filter wastewater; instead, they are located downstream of fixtures and are not intended to serve as filters for solid debris or contaminants. Thus, the role of traps is singularly focused on safeguarding the living environment from unwanted sewer gases.