What is the primary difference between a primary plumbing vent and a secondary vent?

The primary plumbing vent in an RV serves a crucial function by allowing sewer gases to escape to the atmosphere, maintaining proper pressure in the drainage system, and preventing unwanted odors from entering the vehicle. Typically, this vent is located outside the RV, often extending through the roof. This external placement is essential for effective venting.

While a secondary vent may be used within the plumbing system, its primary role is usually to assist the main venting system in more complex layouts, for example, where additional ventilation is necessary due to the design of the plumbing. The choice of option B highlights the essential characteristic of a primary vent being located outside the RV, which is fundamental to its effectiveness in sewer gas management and overall system performance. Understanding this distinction helps RV technicians ensure proper installation and maintenance of venting systems, contributing to the safety and comfort of the vehicle’s occupants.