What is the difference between a “building drain” and a “building sewer”?

The distinction between a "building drain" and a "building sewer" is crucial in plumbing design and installation. A building drain is specifically designed to collect wastewater and convey it away from various plumbing fixtures within a building to a point—typically a building sewer. This function involves receiving the discharge from sinks, toilets, and other appliances before the wastewater is transported further away from the building. Therefore, identifying a building drain as a component that collects wastewater from fixtures aligns accurately with its role in a plumbing system.

In contrast, a building sewer is responsible for transporting that wastewater from the building drain to a municipal sewer system or on-site sewage disposal system. Given this differentiation, it is clear that while the building drain focuses on collection within the building, the building sewer is about the movement of wastewater beyond the building itself. This understanding reinforces the importance of recognizing the specific roles each plays in plumbing infrastructure.