Drain Pipes: These are downward angled pipes that rely on gravity to move water from the fixture and into the sewer line. By observation, you’ll tell this system is more complex than the water supply system: Reliance on gravity has its downsides.
Drain Traps: Drain traps, also called P traps, are U-shaped pipes that prevent backflow in a plumbing system. These pipes also hold water consistently, thanks to their curvature.
Drain Vent: If you turn a bottle of water upside down, water flow is rather hectic. That’s what happens when water flows through a closed system; it’s just not smooth. That’s where drain vents come in.