DWV stands for Drainage, Waste, and Vent system. It is a key component of the building drainage system that collects wastewater from sinks, bathtubs, showers, and other fixtures in the home and sends it to the septic tank or sewer line.The DWV system is basically a series of smaller piping components that get connected to each other in order for wastewater from the fixtures to drain into the waste line.