Where does the building sewer begin?

The building sewer begins 2 feet outside the building wall. This is an important distinction in plumbing terminology, as it marks the transition between the building's plumbing system and the public sewer system or the private septic system. The building sewer typically consists of a pipe that carries wastewater away from the building to the municipal sewer or septic system.

Understanding the exact point where the building sewer starts is crucial for plumbers because it influences the design of plumbing systems, compliance with local codes, and maintenance responsibilities. It is essential for proper installation to ensure that the building sewer is functioning effectively and safely. Starting at a specific distance outside the building wall allows for consistent and standardized installation practices.

The other options describe locations that either fall within the building itself or do not clearly denote the transition point from private plumbing to public infrastructure, which is critical to understand in the context of plumbing systems.