The drainage and vent system in Figure 1 is designed in accordance with the Uniform Plumbing Code. The UPC permits many types of venting systems for protecting the trap seal from siphonage (negative pressure) and backpressure (positive pressure).
The plumbing fixtures are vented using vertical wet vents, the most economical venting design. Vertical wet venting is used for all fixtures that connect to a branch vent. The branch vent connects to the vent stack on each floor.