What type of building sewer specifically conveys sewage only?

The correct choice is the Building Sewer - Sanitary, as it is specifically designed to transport sewage from the building to the public sewer system or to a private sewage treatment system. This type of sewer handles the discharge of waste, including human waste and wastewater from kitchen sinks, showers, and other plumbing fixtures, ensuring that it is appropriately directed for treatment.

The distinction between a sanitary building sewer and other options is critical in plumbing codes and practices. For instance, the Building Sewer - Storm is intended for stormwater management and does not convey sewage, which can lead to contamination issues if combined with sewage. A Building Subdrain is primarily designed for groundwater control and does not handle sewage directly. A Cesspool serves as a form of onsite sewage disposal but primarily holds liquid waste and allows for some seepage into the surrounding soil rather than providing a structured conveyance for sewage to a treatment facility.

Understanding the purpose of these different types of sewer systems is essential for compliance with plumbing codes and for ensuring proper sanitation and environmental protection.