Which type of building sewer conveys both sewage and storm water?

The correct type of building sewer that conveys both sewage and storm water is indeed referred to as a combined building sewer. This system merges two separate flows—sanitary waste from bathrooms, kitchens, and other wastewater sources with storm water runoff from surfaces like roofs, paved streets, and parking lots.

The reason a combined building sewer is identified this way is due to its design purpose. In areas where space for separate sewage and storm systems might be limited, a combined sewer system is used to efficiently manage this dual flow. It is vital for engineers and plumbers to understand this concept to ensure proper design and compliance with local codes and requirements, particularly in flood-prone areas where storm water management is critical.

In contrast, the other types of sewers mentioned serve distinct functions—sanitary sewers deal exclusively with wastewater from sanitary facilities, storm sewers are intended solely for rainwater and melted snow, and drainage sewers would generally refer to systems meant to carry away excess surface water without the inclusion of sanitary waste. Understanding the specific functions of these systems is crucial in planning and managing plumbing and drainage effectively.