How many floors may some codes limit the use of waste stack vents?

The correct answer indicates that some plumbing codes may limit the use of waste stack vents to three floors. This limitation is primarily based on the need for effective venting to ensure proper drainage and prevent trap siphonage in the plumbing system.

When waste stack vents extend too high without proper consideration, it can lead to potential issues with venting efficiency. Venting is necessary to allow air into the plumbing systems, which helps prevent negative pressure that can siphon water out of traps, leading to odors and possible sewage gas backflow into living spaces.

By setting a limit of three floors for waste stack vents, codes aim to balance effective venting and ease of installation while minimizing complications related to venting performance. Systems that exceed this height may require additional venting methods or configurations, such as utilizing additional vent stacks or branch vents to ensure compliance with the plumbing code and the safe performance of the system.