The black valve automatically connects the drain and vent in the drainage and ventilation system, so that when draining, the air opens in a domino-like manner and closes immediately after smooth drainage, preventing odor, pests, and various viruses from the black valve.

The advantage of applying, designing, and constructing a black valve is that it is an economical method that easily solves the problems of negative pressure caused by water being sucked down toilets, bathroom floors, sinks, bathtubs, and sanitary fixtures, destruction of seals caused by various siphons, and positive pressure (counterpressure) that pushes out water by directly supplying air instead of using multiple ventilation pipes and ventilation valves.