Definitions of Terms Related to Home Water
devices that eliminate water hammer. Air chambers 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
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
flowing back of used, contaminated, or polluted water from a plumbing fixture
or vessel into a potable water supply because of negative pressure in the pipe.
Branch—Any part of the piping system other than the main, riser, or
Branch vent—A vent connecting one or more individual vents with a vent
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
physical connection or arrangement between two otherwise separate piping
systems (one of which contains potable water and the other which contains
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.)
Disposal field—An area containing a series of one or more trenches lined
with coarse aggregate and conveying the effluent from a septic tank through
vitrified clay pipe or perforated, nonmetallic pipe, laid in such a manner that
the flow will be distributed with reasonable uniformity into natural soil.
Drain—Any pipe that carries wastewater or waterborne waste in a
building (house) drainage system.
Flood level rim—The top edge of a receptacle from which water overflows.
Flushometer valve—A device that discharges a predetermined quantity of water
to fixtures for flushing purposes and is closed by direct water pressures.
toilet using a flushometer valve that uses pressure from the water supply system rather
than the force of gravity to discharge water into the bowl, designed to use
less water than conventional flush toilets.
Flush valve—A device located at the bottom of the tank for flushing
toilets and similar fixtures.
water heated to at least 120°F (49°C) and used for cooking, cleaning, washing
dishes, and bathing.
Insanitary—Unclean enough to endanger health.
device to separate and retain deleterious, hazardous, or undesirable matter
from normal waste and permit normal sewage or liquid waste to discharge into
the drainage system by gravity.
Main vent—The principal
artery of the venting system, to which vent branches may be connected.
Leader—An exterior drainage pipe for conveying storm water from roof
or gutter drains to the building storm drain, combined building sewer, or other
means of disposal.
Pneumatic—Pertaining to devices making use of compressed air as in
pressure tanks boosted by pumps.
Potable water—Water having no impurities present in amounts sufficient to cause
disease or harmful physiologic effects and conforming in its bacteriologic and
chemical quality to the requirements of the U.S. Environmental Protection
Agency’s Safe Drinking Water Act or meeting the regulations of other agencies
P & T (pressure and temperature) relief valve—A
safety valve installed on a hot water storage tank to limit temperature and
pressure of the water.
P-trap—A trap with a vertical inlet and a horizontal outlet.
Public sewer—A common sewer directly controlled by public authority.
Relief vent—An auxiliary vent that permits additional
circulation of air in or between drainage and systems.
Septic tank—A watertight receptacle that receives the discharge of a building’s
sanitary drain system or part thereof and is designed and constructed to
separate solid from liquid, digest organic matter through a period of
detention, and allow the liquids to discharge into the soil outside of the tank
through a system of open-joint or perforated piping or through a seepage pit.
Sewerage system—A system comprising all piping, appurtenances, and treatment
facilities used for the collection and disposal of sewage, except plumbing
inside and in connection with buildings served, and the building drain.
Soil pipe—The pipe that directs the sewage of a house
to the receiving sewer, building drain or building sewer.
Soil stack—The vertical piping that terminates in a roof
vent and carries off the vapors of a plumbing system.
Stack vent—An extension of a solid or waste stack above
the highest horizontal drain connected to the stack, sometimes called a waste
vent or a soil vent.
Storm sewer—A sewer used for conveying rain water,
surface water, condensate, cooling water, or similar liquid waste.
Trap—A fitting or device that provides a liquid seal to prevent
the emission of sewer gases without materially affecting the flow of sewage or
wastewater through it.
Vacuum breaker—A device to prevent backflow (back siphonage) by means of an opening through which air may be
drawn to relieve negative pressure (vacuum).
Vapor lock—A bubble of air that restricts the flow of
water in a pipe.
Vent stack—The vertical vent pipe installed to provide
air circulation to and from the drainage system and that extends through one or
Water hammer—The loud thump of water in a pipe when a
valve or faucet is suddenly closed.
Water service pipe—The pipe from the water main or other sources
of potable water supply to the water-distributing system of the building
Water supply system—Consists of the water service pipe, the water-distributing pipes, the
necessary connecting pipes, fittings, control valves, and all appurtenances in
or adjacent to the building or premises.
Wet vent—A vent that receives the discharge of waste
other than from water closets.
Yoke vent—A pipe connecting upward from a soil or waste
stack to a vent stack to prevent pressure changes in the stacks.