What is the main function of a building drain?

The main function of a building drain is to conduct sewage discharge from various fixtures within the building to the main sewer system. This is crucial for maintaining proper sanitation and hygiene within the building. The building drain collects wastewater from sources like sinks, toilets, showers, and other plumbing fixtures and transports this waste away from the interior spaces. By efficiently channeling this sewage outside, it ensures that waste does not accumulate within the building, preventing potential health risks and structural damage.

While other functions mentioned in the options are important in plumbing systems, they do not describe the fundamental role of a building drain. For example, collecting stormwater runoff pertains to a different system designed for managing rainwater rather than sewage. Separating greywater from blackwater is an essential practice for wastewater management, but it refers to a process that occurs after the sewage is discharged, not a function of the building drain itself. Providing access for maintenance is necessary in plumbing systems, but it is not the primary purpose of a building drain; it relates more to plumbing fixtures or access points within the overall drainage system.