Under which condition is a cleanout not required at the junction of a building drain and building sewer?

A cleanout is a vital feature in plumbing systems, allowing for easy access to the drain lines for maintenance and cleaning. The requirement for cleanouts is determined by specific conditions, one of which relates to the installation of a cleanout in relation to a building drain and building sewer connection.

The correct answer indicates that a cleanout is not required at the junction when a cleanout is installed in a three-inch or larger stack within ten feet of that junction. This is based on plumbing code provisions that allow for cleanouts to serve multiple drains. When a cleanout is present nearby, it provides adequate access to the drainage system for maintenance reasons, thereby negating the need for an additional cleanout directly at the junction. This means that as long as there is a sufficiently sized and placed cleanout within the specified distance, the system maintains its functionality and accessibility.

Choosing this option reflects an understanding of plumbing code regulations that prioritize efficiency and accessibility in plumbing design, while ensuring that maintenance needs can still be met without redundancy in cleanout installations.