Final answer:
The deciding factor when deciding between circuit vent or wet vent in plumbing is based on plumbing code requirements and the specific layout of the plumbing system.
Step-by-step explanation:
In plumbing, circuit vents and wet vents are two methods used to vent drainage systems. The deciding factor between the two is mostly based on the plumbing code requirements and the specific layout of the plumbing system.
A circuit vent is a single vent pipe that serves multiple fixtures, typically located downstream from them. It is used when the fixtures are close together and can be adequately vented by a single vent pipe.
A wet vent is a vent pipe that also serves as a drain pipe for one or more fixtures. It is used when the fixtures are farther apart and the plumbing code allows the use of a wet vent to save on materials and space.