What is the purpose of the building drain in a plumbing system?

The purpose of the building drain is to receive discharge from soil, waste, and other drainage pipes. This component of the plumbing system is crucial as it collects wastewater from fixtures, such as sinks, toilets, and showers, and directs it toward the municipal sewer system or a septic tank. The building drain is designed to effectively transport these waste materials while ensuring that the plumbing system remains flowing and functioning correctly.

By properly managing the discharge of waste, the building drain plays a vital role in maintaining sanitary conditions within the building and preventing the buildup of harmful substances. Additionally, the design of the building drain includes features such as proper slope and size to facilitate optimal flow of waste materials, reducing the risk of blockages.

In contrast, the other options do not align with the fundamental purpose of the building drain. Adding pressure to the drainage system is not a function of the drain; rather, gravity typically aids in the movement of waste. Discharging stormwater is a separate function typically managed by a storm drainage system, rather than through the building drain. Ventilating the drainage system is essential for preventing vacuum and allowing proper airflow, but it is the function of the venting system, not the building drain itself.