What is the key feature of a wet vent system?

A wet vent system is designed to allow multiple fixtures to share a single vent stack, which enhances efficiency in plumbing design. The primary feature of this system is that it combines the functions of both drainage and venting for various fixtures, such as sinks, toilets, and showers, within the same vertical pipe.

This approach reduces the requirement for additional vent pipes, ultimately leading to a simpler and more cost-effective installation. In environments where space and resources are limited, a wet vent system can effectively manage the venting of air while simultaneously providing a pathway for wastewater to flow away, ensuring that the system maintains proper drainage and prevents siphoning of traps.

Understanding this functionality makes it clear why the other answers do not fit. A wet vent system does not serve just a single fixture; by design, it supports multiple fixtures. Additionally, it operates under neutral pressure rather than negative pressure, ensuring that drainage flows smoothly without the risk of back pressure. Finally, it is not exclusively for solid waste; the wet vent can accommodate both solid and liquid waste, making it versatile in various plumbing applications.