Which venting system allows one vent to serve two traps?

The system that allows one vent to serve two traps is known as a unit vent. In plumbing design, a unit vent connects multiple fixtures, providing a single vent for their drainage systems. This configuration helps maintain proper pressure in the drainage system while promoting effective air circulation and preventing the siphoning of trap seals, which can lead to odors and other issues. The efficiency of a unit vent reduces the number of pipes needed and simplifies the overall plumbing installation, creating a more manageable and cost-effective solution.

Other venting systems, such as relief vents, wet vents, and local vents, serve different purposes and scenarios. Relief vents are typically used to prevent overpressure in siphonic systems, while wet vents allow for a single vent to simultaneously serve as both a drain and a vent for multiple fixtures in certain configurations. Local vents are designed for specific fixtures but do not serve multiple traps in the way a unit vent does. Hence, the unit vent's functionality is crucial for optimizing space and efficiency in plumbing systems.