What is the minimum height of a trap arm vertical from the trap outlet?

The minimum height of a trap arm vertical from the trap outlet is established to ensure proper drainage and prevent potential backflow or siphoning issues within the plumbing system. According to plumbing codes, maintaining the specified vertical height provides sufficient gravitational force for waste to flow efficiently through the drainage system while supporting the trap's functionality of retaining a water seal that prevents sewer gases from entering the living space.

In this context, the correct height of 6 inches is critical, as it meets the minimum requirement to effectively manage the drainage of the fixture without creating undue pressure or obstruction. This specification also helps ensure compliance with safety regulations and optimizes the plumbing system's overall performance. The other options suggest heights that exceed the minimum requirement but are not necessary for function while potentially introducing unnecessary complexity to the installation.