by William Rose The Mysteries of Plumbing Drains Unveiled Water runs downhill and Friday's payday. That's all there is to plumbing. Well, not quite. When you start thinking of all that can go wrong in a plumbing system, you realize that gravity is a part, but not the whole story. A residential plumbing system has three components: water supply, fixtures, and drain/waste/vent (DWV). The water supply can leak, freeze, hammer, and lose pressure. Fixtures can break, clog, backflow, and drip. DWV can leak, clog, gurgle, and stink. Plumbing fixtures and water supply, however, are pretty simple compared to DWV systems, which can get pretty complicated. This article hopes to shed some light on the mysteries of DWV. The science of plumbing is,