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

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

Answer: (B)

The essential idea is that sanitary waste from the building must go into the building sewer. When any part of an above‑ground building drain discharges to a vertical pipe, that waste path is part of the sanitary drainage system and should feed into the building sewer, which is the private drain line from the building to the public sewer (or private disposal). This arrangement keeps sanitary sewage on its proper path with the right slope, venting, and backflow protection, and it separates it from stormwater and potable-water systems. Connecting to a water main would contaminate drinking water, and tying into a storm sewer would send sanitary sewage to a storm system not designed to handle it. Although the building sewer ultimately connects to the public sewer main, the direct connection the code requires for the building drain is to the building sewer.