Holding tank
A holding tank, also called a waste water holding tank or black (water) tank, is a container for storing sewage in vehicles equipped with toilets. Vehicles that employ holding tanks include recreational vehicles (RVs), trucks (U.S. usage) or lorries (UK usage), railroad trains, boats, aircraft, and even spacecraft. The contents are emptied into a dump station, which discharges the raw sewage into a sewage treatment system.