Drain Pipes and Plumbing

The Drain-Waste-Vent (DWV) System: is the system of pipes that carries water and waste to a sewer line or septic tank. The DWV System is made up of three parts:

1. Drain lines carry water from tubs, showers, and sinks.
2. Waste lines transport waste from toilets.
3. Vent lines provide the necessary air pressure to allow waste to flow freely and expel sewer gases.

All waste and drain lines slope downward slightly from the fixture toward the septic or sewer system. Gravity carries waste and water (hence, the old axiom about stuff rolling downhill).

Pipes are rather large in diameter to minimize the possibility of blockages. Most plumbing pipes measure from 1 1/4 inches to 4 inches. Different sizes have different uses. The table below illustrates which size pipes serve which purpose.

• Most drain piping is made of cast iron, plastic, or copper (although some older homes may have pipes made of lead, which can be a huge health and safety issue in and of itself). Some vent pipes are galvanized iron.
• By definition, a "drain" is a vessel by which unwanted water is flumed away, funneled into a receptacle, or run into the sewers as waste.
• In order to operate safely and properly, each drain must be served by a vent line that carries sewer gases out through the roof. As long as there is no drain above the connection point, several vents may be connected together and joined to the soil stack. Another option is to have vents may pass through the roof on their own.
• Cleanouts are Y-shaped fittings in the line that are capped off. It is essential for all waste lines to have cleanouts at easily accessible locations, so that if a blockage occurs, a plumber has easy access to snake out the line.
• A trap is a curved section of drain pipe that fills up with water. Traps are necessary to provide seals for preventing odors and sewer gases from entering the building structure.
• A P-trap is used for a drain that penetrates a wall. have, and those that go through the floor have an
• An S-trap is used for a drain that goes through the floor. Each time the fixture is used, the water held by the trap is replaced.