What is the term for the portion of a drainage system that doesn’t drain by gravity into the building sewer?

The term for the portion of a drainage system that does not drain by gravity into the building sewer is referred to as a building subdrain. This component is designed primarily to manage groundwater or surface water, collecting water from areas such as basements or under structures and directing it away to prevent flooding or structural damage.

It is important to note that while other terms, such as cesspool, circuit vent, and common vent, relate to different functions within plumbing systems, they do not accurately describe the specific aspect of a drainage system that deals with the non-gravity draining components. A cesspool is typically a pit that collects sewage, a circuit vent is related to roof drainage systems to help maintain airflow within drainage pipes, and a common vent connects two or more fixtures to provide proper air flow. Thus, the building subdrain is specifically formulated for managing drainage that does not utilize gravity to move waste, which highlights its unique role within a plumbing system.