Fixture vent

In the plumbing trade fixture vents are used to ventilate plumbing fixtures, to prevent siphonage, to relieve pressure on trap seals, and to draw off back pressure from gases generated by decomposing sewage. It is usually run as a continuous vent, that is, only one fitting is used to connect vent pipe, waste pipe, and fixture trap or branch.

This is most often accomplished by the use of a T-Y fitting. Each fixture should be vented and trapped separately so that trouble with any one fixture will not affect any other part of the system.