When should a plumbing system be vented?

A plumbing system should be vented when it discharges into a building sewer. Venting is essential for allowing sewer gases to escape safely into the atmosphere and for maintaining proper air pressure within the drainage system. When waste is discharged into a building sewer, vent lines provide the necessary air circulation to prevent vacuum conditions that could hinder drainage or siphon traps dry, leading to potential sewer gas intrusion.

Proper venting also helps to prevent backups and ensures that fixtures drain effectively. Without adequate venting, the flow of water can create negative pressure, causing slow drainage and increasing the risk of clogs within the plumbing system. Therefore, when a plumbing system connects directly to a building sewer, it necessitates a vent to function correctly and safely.