If any portion of an above-ground building drain discharges to a vertical pipe, to what must the building drain connect?

• A. The storm sewer.
• B. The building sewer.
• C. The sanitary lateral.
• D. The groundwater drainage line.

Answer: (B)

The key idea is that sanitary waste from inside a building must stay on the sanitary drainage path from the point of discharge onward. If any portion of an above-ground building drain feeds into a vertical waste/vent line, it is designed to continue downstream into the building sewer. The building sewer is the dedicated pipe that carries wastewater from the building to the public sewer or a private disposal system. Storm sewers handle rainwater and are not suited for sanitary waste, and groundwater drainage lines are for groundwater, not sanitary effluent. The sanitary lateral is the outside connection to the municipal system, but the immediate Receiving line for the building drain is the building sewer, ensuring all sanitary waste follows the proper sanitary route.