What is the purpose of a trap in plumbing?

The primary purpose of a trap in plumbing is to prevent sewer gases from entering the building. Traps create a water seal that blocks the passage of noxious gases while still allowing wastewater to flow through the drainage system. This seal is established by holding a small amount of water in the trap, which acts as a barrier.

The functionality of traps is crucial in maintaining indoor air quality and protecting occupants from harmful fumes that can cause health issues. Moreover, traps are commonly found in sinks, toilets, and floor drains, contributing to the effectiveness of the entire plumbing system. The water seal in traps also helps to prevent pests from entering the building through the sewage lines, further enhancing safety and hygiene.

Other options, such as allowing water to flow freely, storing wastewater, or filtering waste from clean water, do not accurately represent the vital role traps play within the plumbing system. While water must flow for proper drainage, the specific feature that defines a trap is its ability to maintain a barrier against gases, making it an essential component in plumbing design.