Bathroom Plumbing – Drain, Waste, Vent System

The DWV system empties into the house’s septic system or into a municipal sewer and relies on gravity rather than water pressure to move fluids through the system. In addition to drain and waste pipes that carry liquid Vent Issue Drain and solid waste away, a DWV system consists of vent lines that provide an exit route for sewer gases and that equalize atmospheric pressure within the DWV system, allowing liquids to flow freely down and out.
Vents are required at each trap location and eventually link back up with the soil stack, which is then vented through the roof. Traps- curved sections of pipe that retain water-block sewer gases from entering the house through the fixture. Because DWV systems rely on gravity, they must always be sloped a minimum of 1/8in. per ft., though the optimal slope is 1/4in. Advantages Of Being A Plumber per ft. Any slope greater than 1/2in. per ft. tends to make liquid and solid waste separate, leaving the solid waste behind and eventually possibly clogging up the system. In addition, DWV pipes are typically large in diameter, which can sometimes make it difficult to route them through framing. Cast iron and plastic are the two most common DWV pipe materials.
Copper is also sometimes used, though the materials are more expensive and sweating joints is more time-consuming. Sometimes threaded galvanized steel is still used, but it is more often seen in older installations and renovation work. Again, local building codes usually specify which type of pipe is acceptable and which is not, as well as whether or not pipe materials can be mixed. In general, plastic is the easiest and least-expensive pipe to work with. It’s lightweight, and different sizes of pipe and fittings are readily available. Cemented joints are very resistant to leaks, particularly when there is movement or vibration, so plastic is particularly suited for use with jetted tubs. ABS and PVC are the two common types of plastic pipe used; local building codes typically specify the use of one or the other, but usually not both.
It’s easy to tell the two pipes apart: ABS is black or charcoal-gray, while PVC is white or cream. Give serious consideration to using no-hub cast iron for second-floor drains. Even though it’s more expensive and harder to work with than plastic, iron pipe is considerably less noisy, a real consideration when an upstairs bathroom is over a living space. Plastic or copper pipe can be insulated to reduce noise but will still probably be noisier than cast iron. There is nothing quite so disruptive to a dinner party as the sound of Niagara Falls rushing overhead when the upstairs toilet is flushed.

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