Guide to Plumbing Installation For Beginners

A soil pipe in a plumbing system acts as a drainage pipe that carried or is designed to carry human excrement.
If a pipe is vertical it is called a stack and if it is horizontal it is called a branch. A waste pipe carried liquid wastes that do not include human excrement.
Vent pipes, with few exceptions, are attached to the drainage piped near the traps, and between the trap and the sewer for purpose of admitting air or taking air away from the drainage pipes.
The vent pipes should lead to the outside air at some distance from any other opening into the building. Ventilating and drainage pipes at distance from any other opening into the building.
Ventilating and drainage pipes at a point near the trap assist in prevailing the trap seal from being broken by air pressure in the drainage pipes preventing the trap seal from being broken by air pressure in the drainage pipes.