Which component is part of the Building Drain system?

The building drain system is primarily responsible for transporting wastewater from the fixtures within a building to the main sewer line. Drainage from inside walls is indeed a significant component of this system, as it encompasses the piping that carries wastewater from sinks, toilets, showers, and other plumbing fixtures through the structural walls of a building before it is directed to the sewer.

The interior drainage system must be adequately installed to ensure proper flow and to prevent issues like blockages or leaks, which can lead to serious damage and sanitary concerns. The integration of the drainage from inside walls into the building drain system is essential for effective wastewater management and compliance with plumbing codes.

In contrast, the other components mentioned serve different purposes: sewer ejector pumps are used for pumping wastewater from lower elevation areas to higher elevations; outdoor storm drains are meant for managing surface rainwater and preventing flooding; and exterior building overflow devices deal with excess water that may accumulate on roofs or surfaces. These components do not constitute part of the building drain system, which is specifically tasked with collection and transport of wastewater generated inside the structure.