Plumbing drainage system

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.

Other definitions of smaller parts of the drainage system include:

Fixture: Any receptacle intended to receive or discharge water or water-carried waste into the drainage system.

Main: Any system of horizontal, vertical, or continuous piping to which fixtures are connected either directly or through the use of branches.

Branch: That part of the plumbing system which extends from the main to a fixture.

Leader: Any vertical line of piping which receives and carries rain water.

Fitting: Any one of a number of devices used to connect pieces of pipe or change the direction of pipe.

Plumbing basics

Bathroom fixtures
Bathroom floor plans
Bathtub installation
Installing lavatory
Water closet install

Cesspool / septic tanks

Fixture pipes
House drain
House sewer
Soil stack
Vent piping

Finishing touch

Heating a home


Dishwasher install
Garbage disposer install
Kitchen plans
Kitchen sink installation
Laundry install
Room plans
Work areas

Cast Iron

Plumbing layout
Pipe plan
Water distributing

Faucet repair
Pipe problems
Repair other
Toilet repair


Plumbing materials
Specialty tools

Water Supply

Hot water heaters
Running pipes
Service connection
Water meter
Water savings

Wells / pumps