The building sewer is that part of the horizontal drainage piping that begins at what distance outside the building wall?

The building sewer is defined as the section of the drainage system that transfers wastewater from the building's plumbing to the municipal sewer line or to an on-site disposal system. The beginning of the building sewer is specifically marked at a standard distance from the building wall to ensure proper drainage and to accommodate any necessary connections.

In plumbing codes, the standard distance for the building sewer to begin is typically set at 30 inches outside the building wall. This measurement is crucial because it provides enough space to install the sewer line while also allowing for proper slope and drainage management. It helps to prevent potential issues such as backflow, which can occur if the sewer line is too close to the foundation or if proper fall cannot be achieved.

Understanding this specification is important for plumbing professionals, as it ensures compliance with regulations and contributes to overall system efficiency.