What is the purpose of a trap in plumbing?

A trap in plumbing serves the essential function of preventing sewer gas from entering buildings. It achieves this by maintaining a water seal, which acts as a barrier between the plumbing system and the living space. This water seal is created when a small amount of water is retained in the trap after use.

Sewer gases can be harmful if they infiltrate indoor spaces, causing potential health risks and unpleasant odors. The design of the trap, typically shaped like a U or S, ensures that even if there is no flow of water, the standing water in the trap effectively blocks the gases from traveling back up through the drain. This vital safety feature is crucial for maintaining a healthy and safe indoor environment.

While other components in plumbing may regulate pressure, store water, or facilitate drainage, the unique and primary purpose of a trap is safeguarding against sewer gases.