What is that vent pipe in plumbing that serves the building drain and building sewer?

The vent pipe that serves both the building drain and the building sewer is known as a relief vent. Its primary function is to allow gases to escape from the plumbing system and to maintain proper pressure within the drainage system. By facilitating airflow, the relief vent helps to prevent siphoning, ensuring that the traps in the plumbing system retain water and continue to function correctly. This is crucial in preventing sewer gases from entering the habitable spaces of the building.

In plumbing systems, different types of vents serve specific roles. The vent stack through the roof is more about venting the system to the outside air and is typically located vertically. A yoke vent connects two or more plumbing fixtures to ensure that they can equally share venting. Similarly, the acronym SVTR may refer to a specific type of vent stack but is not widely recognized in the sense that a relief vent is. The relief vent, therefore, stands out as the key component that directly connects both the building drain and the sewer, addressing the needs for pressure balance and gas escape effectively.