A cleanout is required at the junction between a building drain and which of the following?

A cleanout is essential at the junction between a building drain and the building sewer to facilitate maintenance and ensure proper drainage. This cleanout allows for easy access to the drainage system, enabling plumbers to clear any blockages that may occur between the building and the municipal sewer system or septic tank.

The building drain is the part of the plumbing system that collects wastewater from the building, while the building sewer connects this drain to the system that carries the wastewater away. Providing a cleanout at this critical transition point is vital to ensure that any obstructions can be addressed efficiently.

Using cleanouts at strategic points is a best practice in plumbing to maintain an effective drainage system, avoid potential backups, and minimize property damage. This is particularly necessary where changes in direction and junctions occur, as these are common locations for blockages to form.