The drainage system is that series of pipes which receives, carries, and removes waste and rain water, other liquids, and human excreta from fixtures to a sewer or other disposal receptacle. This system is divided into several sections, each of which is defined below.

Parts of drainage system

House sewer: That section of pipe which runs between the house drainage system and the connection to the public sewer or septic tank. House sewers should convey the waste of only one residence.

House drain: The lowest piping in a house drainage system, this pipe receives the discharge from soil, waste, and other drainage pipes, and then carries such discharge to the house sewer. The house drain ends just outside the front or foundation wall of the building, and operates by gravity.

Soil stack and pipe: Any line of pipe which carries the discharge of water closets. The term “stack” refers to the vertical runs of such piping.

Waste stack and pipe: All pipe receiving the discharge of fixtures other than water closets. An indirect waste pipe does not connect directly with either the house drain or the soil or the waste stack, but usually ends over and above the overflow rim of fixture that is water-supplied, trapped, and vented.

Trap: Refers to a fitting or device constructed to prevent the passage of air or gas back through a pipe or fixture, without materially affecting the flow of sewage or waste water.

Vent piping: Provides ventilation to the drainage system and prevents trap siphonage and back pressure from clogging or contaminating the drainage system. Local ventilating pipe is a duct or pipe connected to the house side of a fixture or trap through which foul vapors may be removed from a room.

Sub-house drain: Any portion of the drainage system which cannot drain by gravity but which still handles the disposal of waste sewage.