What is the piping that runs from a soil, waste, and vent stack to the fixture trap called?

The piping that runs from a soil, waste, and vent stack to the fixture trap is referred to as a fixture branch. This term specifically describes the segment of the plumbing system that connects the main stack to the individual fixtures within a building, allowing wastewater and sewage to flow from the fixture into the waste system.

Understanding this term is crucial in plumbing design and installation because it helps delineate the parts of the drainage system. The fixture branch serves to connect different components of the plumbing, ensuring that the flow of waste is routed correctly and that fixtures function properly. By ensuring a dedicated pipe line is established, it helps maintain proper drainage and venting within the overall plumbing system.

The other choices represent different plumbing components—while a drain line refers to any line carrying wastewater away, a trap connection specifically pertains to the connection point of a trap to a fixture. A vent pipe, on the other hand, is designed to allow air into the system to prevent vacuum formation. Each term has its unique purpose in plumbing, but "fixture branch" is the only term that specifically indicates the line connecting the stack to the fixture trap.