Plumbing Terms

Plumbing may be defined as the practice, materials and fixtures used in the installation, maintenance and alteration of all piping, fixtures, appliances and appurtenances in connection with sanitary and storm drainage facilities, the venting system, and public and private water supply systems. Plumbing does not include the trade of drilling water wells, installing water-softening equipment, or the business of manufacturing or selling plumbing fixtures, appliances, equipment or hardware. A plumbing system consists of three separate parts: an adequate potable water supply system; a safe, adequate drainage system; and ample fixtures and equipment.

Background Factors

The generalized inspection of a home is concerned with a safe water supply system, an adequate drainage system, and ample and proper fixtures and equipment. This article explains features of a residential plumbing system, and the basic plumbing terms the inspector must know and understand to properly identify housing code violations involving plumbing and the more complicated defects that s/he will refer to the appropriate agencies. Only InterNACHI inspectors are sufficiently trained to spot complicated defects that others will overlook. 

Definitions

Air Chambers

Pressure absorbing devices that eliminate water hammer. They should be installed as close as possible to the valves or faucet and at the end of long runs of pipe.

Air Gap (Drainage System)

The unobstructed vertical distance through the free atmosphere between the outlet of a water pipe and the flood level rim of the receptacle into which it is discharging.

Air Gap (Water Distribution System)

The unobstructed vertical distance through the free atmosphere between the lowest opening from any pipe or faucet supplying water to a tank, plumbing fixture, or other device and the flood level rim of the receptacle.

Air Lock

An air lock is a bubble of air which restricts the flow of water in a pipe.

Backflow

The flow of water or other liquids, mixtures, or substances into the distributing pipes of a potable water supply from any source or sources other than the intended source. Back siphonage is one type of backflow.

Back Siphonage 

The flowing back of used, contaminated, or polluted water from a plumbing fixture or vessel into a potable water supply due to a negative pressure in the pipe.

Branch

Any part of the piping system other than the main, riser, or stack.

Branch Vent 

A vent connecting one or more individual vents with a vent stack.

Building Drain

The part of the lowest piping of a drainage system that receives the discharge from soil, waste, or other drainage pipes inside the walls of the building (house) and conveys it to the building sewer beginning 3 feet outside the building wall.

Cross Connection

Any physical connection or arrangement between two otherwise separate piping systems, one of which contains potable water and the other either water of unknown or questionable safety or steam, gas, or chemical whereby there may be a flow from one system to the other, the direction of flow depending on the pressure differential between the two systems. (See Backflow and Back siphonage.)

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