Where any portion of an above-ground building drain discharges to a vertical pipe, the building drain shall connect to which?

• A. Building sewer
• B. Building water main
• C. Storm sewer
• D. Public sewer

Answer: (A)

In drainage terminology, the path from inside the building to the public system is split into the building drain and the building sewer. If any part of an above-ground building drain ends up discharging into a vertical pipe, it must join the building sewer. The building sewer is the main sanitary conduit that carries wastewater from the building out to the public or private disposal system. This keeps sanitary waste on a dedicated sanitary path, away from vent stacks and storm sewers, and ensures proper venting and trap protection along the way. Connecting directly to a water supply line, a storm sewer, or bypassing the building sewer to reach the public sewer would mix systems or misuse venting, which is not allowed.