Plumber's Licensing Exam: Glossary of Important Plumbing Terms

The following glossary is meant as a tool to prepare you for the plumber’s licensing exam. You will not be asked any vocabulary questions on the exam, so there is no need to memorize any of these terms or definitions. However, reading through this list will familiarize you with general words and concepts, as well as terms you may encounter in the exam questions.
 

A
ADA Americans with Disabilities Act.: Enacted in 1990, this federal act created regulations that guarantee access of public areas to people with various disabilities. Some of the requirements include ramps for wheelchairs, grab bars, and larger toilet areas to accommodate wheelchairs.
adhesion : an attraction between different materials on a molecular basis.
air admittance valve: a one-way valve that closes by gravity. This allows air to be drawn into a drainage system when negative pressure exists, such as that created when a slug of water travels down it, but does not allow air or sewer gasses into the building through the valve.
air break : an indirect waste that discharges into a receptor below the flood-level rim of the receptor.
air gap : an indirect waste that discharges into a receptor above the flood-level rim of the receptor.
ambient: the area surrounding something; often referred to as room temperature for plumbing purposes.
aquastat : a device that controls the water temperature in a vessel or in piping. An aquastat has a sensing probe, either inside the water vessel or mounted on the surface. This actuates the manually set control that turns the heating appliance on or off according to the water temperature desired. Aquastats are always in hydronic (heat distributed by water) systems.
ASME : American Society of Mechanical Engineers. The ASME has researched, created, and published many engineering standards, including those for piping and storage systems for medical gasses.
 

B
backflow preventer: a system of check valves of various configurations that allow flow in one direction and securely prevent flow in the opposite direction.
black water: water that contains human bodily waste.
BTU : British Thermal Unit, a measurement of heat. The amount of heat required to raise one pound of liquid water 1°F is 1 BTU.
building drain the lowest (with the exception of subdrains) horizontal part of a drain system within a building that receives all the drainage from the fixtures within the building and extends to 30 inches outside the exterior wall of the building.
building sewer: the final part of a building drain system that begins where the building drain ends, 30 inches beyond the exterior wall of the building. It then extends to the sewage disposal system, be it the public sewer main, a septic system, or other sewage disposal system.
 

C
closet carrier : a cast iron and steel structure that is concealed in the wall and is used to support a wall-mounted closet.
concealed fouling surface: from the definitions section of the IPC, a concealed fouling surface is “any surface of a plumbing fixture which is not readily visible and is not scoured or cleansed with each fixture operation.”  This definition also includes the surface of the wall or floor adjacent to and covered by the fixture body.
conductor: a pipe inside a building that carries storm water from a roof drain to the storm drain or a combined drain.
constant: a number that is always the same in a particular mathematical equation.
 

D
DFU: drainage fixture unit. A number used to measure the load impact of a fixture on the drainage system.
dielectric unions: a type of three-part union that is usually half galvanized and half brass. Between the galvanized and brass sections is a plastic insert that prevents galvanic corrosion between the two metals. Any time two pipes of dissimilar metals are joined, it’s a good idea to install a dielectric union to reduce corrosion.
domestic: hot water potable water supplied by the building water distribution system, which has been heated for residential use at sinks, lavatories, baths, showers, a laundry, or any other residential heated water application.
 

E
effluent: the liquid waste discharged from a drainage pipe.
 

F
flashing: a system of sealing layers around a pipe or device that passes through a surface, which is designed to prevent water from entering a roof or wall through the penetration.
flow pressure : the pressure in the water supply pipe near the faucet or water outlet while the faucet or water outlet is wide open and flowing.
flush tank: a tank equipped with a valve that automatically refills it. When actuated, water is released from the tank by gravity into the fixture to be flushed.
flushometer tank : a tank equipped with another pressure tank that fills with water, compressing the air captured inside it until an equal pressure of water and air is achieved. When actuated, the compressed air forces the water out of the tank and into the fixture to be flushed.
flushometer valve : a valve that is connected to a water line under pressure and uses that water pressure to flush a fixture. The flushometer automatically closes after the prescribed amount of water needed for the flush has passed through it.
 

G
GPF: gallon(s) per flush.
grade: for our purposes, the level of the earth where it meets a building.
gray water: water drained from showers, bathtubs, automatic clothes washers, laundry trays, and lavatories. This is water that has no human bodily waste or food waste.
green: environmentally friendly.
 

H
head : the pressure at the bottom of a certain height of a column of a liquid.
hoar frost: a buildup of frost over a period of time when condensation contacts a cold surface and freezes.
hydraulic jump: water rises to a depth greater than a half pipe in the horizontal pipe at a distance within 10 pipe diameters of the vertical stack. This is caused by the sudden slowing of the velocity of the water from the approximately 10 feet per second it attains in the vertical pipe to the pace of 2 feet per second in the horizontal pipe sloped at 1/4-inch per foot. As the water slows, it “stacks up” like traffic at a tollbooth until it can resume a steady flow at a slower pace.
 

I
ID: inside diameter or nominal diameter.
indirect waste: a waste pipe that is not directly connected to the drainage system of the building. It ends above a receptor such as a floor drain or floor sink. The end of the indirect waste pipe is suspended above the receptor a minimum of 1 inch to prevent a backup in the drainage system from entering the indirect waste pipe.
individual water supply: a water supply that is not supplied by or approved by a public entity. Individual water supplies can be from wells, springs, streams, or cisterns. If surface water is utilized as the water supply, it must be appropriately treated to ensure its potability.
invert: the bottom portion of a drainage pipe. The part of the pipe where the waste flows in a stream.
 

L
local vent: a vent that connects to a fixture on the building side of the fixture trap to vent foul odors from the air in the fixture and extends through the roof. Local vents are commonly found on bedpan washers.
 

N
natural gas : a naturally occurring combination of flammable gasses found underground in pockets of certain rocks. It can be used as is, and it is lighter than air. Natural gas is customarily delivered to the point of use by underground pipelines and is metered at the service entrance to the building. If there is a natural gas leak in a building, it will not settle in the lower portions of the building, but will rise and usually exit the building through the roof venting system.
971/2% design temperature : the temperature in a particular area will be above this temperature 971/2% of the time. If the outdoor winter design temperature is 30°F, this means that the temperature in the winter will be 30°F or higher 971/2% of the time. Charts have been created by the National Oceanic and Atmospheric Administration (NOAA) that provide the 971/2% temperature for a number of localities in every state of the United States.
 

O
offset: a combination of fittings that change the location of a pipe, but ends with it continuing in the same original direction. This is commonly done to move around an obstruction such as a beam or post.
oxidation: the chemical process that results when an element combines with oxygen, such as rusting or burning.
 

P
plenum: a space or box, up to room size, that is used for distribution and pressure balance of air throughout a building that has been conditioned by heating, cooling, humidification, dehumidification, filtering, or other treatment. A plenum is not intended to be for habitation. A distribution system of ducts is generally the distribution means attached to a plenum.
potable: water that is free from impurities that would cause harm if ingested and is therefore suitable for drinking.
primary roof drain : a grate in a roof at a low point that is connected to a conductor with the purpose of collecting rainwater and transporting it to the storm drainage system.
propane gas: a by-product of the refining process of oil. It is burned as a gas, but it is usually compressed into a liquid (liquefied petroleum gas, LPG) for easy transport and delivery. Propane is most often stored in tanks at the site where it is consumed. Leaking propane can collect in explosive pools in crawl spaces, basements, and other low portions of a building since it is heavier than air.
psi: pounds per square inch, or, the force exerted on 1 square inch of a surface, such as that created on the inside of a water tank by the pressure from the water supply pipe or the added pressure exerted by the expansion of water being heated in the water heater.
psig: pounds per square inch, gauge. This is pressure expressed in pounds per square inch above normal atmospheric pressure. Normal atmospheric pressure is 14.7 psi. Psig is a measurement of pressure greater than 14.7 psi, using 14.7 psi as zero.
 

S
sanitary drainage system: a drainage system that carries sewage. It does not carry any surface water, storm runoff, or groundwater. This system receives its supply from the plumbing fixtures in a building and nowhere else.
scupper: rectangular holes in the wall at a height demanded by the load-bearing ability of the roof for the purpose of removing rainwater that has collected on the roof when the primary roof drain cannot carry all the water away.
secondary roof drain: a construction method, usually accomplished with scuppers, that conducts rainwater off a roof to a location that is obvious to an observer, who can recognize that the primary roof drain is not removing all the water.
stack vent: the vertical extension of a soil stack above the point of any fixture branch. The stack vent conducts no waste.
station outlet: the point, usually mounted on a wall, where the user makes connections to use the medical gas.
subsoil drain a buried drainage system, usually around the footing of a building, designed to carry water in the soil near the footing away from the building.
sump: a pit designed for the collection of water.
sump pump: a pump placed inside a sump for the removal of the water collected in the sump.
 

T
thermostat : a device that regulates the temperature in a building or a section of a building. A thermostat does this by turning a heating or cooling system on or off according to a manually determined setting. Temperature in the room is sensed by various means, including thermistors, bimetallic strips, bimetallic discs, gas expansion, thermo couples, and thermopiles.
Transite pipe: a brand name of asbestos cement pipe manufactured by the Johns-Manville Company. The name “Transite” has become synonymous with asbestos cement pipe, since Johns-Manville was the largest manufacturer of the product.
trap seal : the distance vertically from the trap weir, or point of overflow into the drain, to the top of the dip of the trap. As long as there is water in this area, no sewer gas can enter the building through the trap.
 

V
vacuum drainage system: a vacuum pump connected to a receiving tank creates a vacuum condition in the drainage system. Fixtures are emptied by opening a valve in the drain, which allows atmospheric pressure to push the waste and water down the drain to the receiving tank.
vacuum relief valve: also known as a vacuum breaker, this device consists of a one-way check valve along with a means for allowing air into the outlet: side of the valve when the water supply is off. This construction prevents backflow into the supply piping and prevents a siphon from occurring in the outlet pipe.
vent : stack a vertical pipe connecting at or near the base of the stack it serves and extending through the roof of the building, used only for conducting air and sewer gas. No waste flows in a vent stack.
 

W
WC : water column. This is the pressure required to create a differential of a certain number of inches in a U-shaped tube. It is used primarily for measuring small pressures similar to those found in end-user gas supplies.
weir : the point in a trap where the water overflows the trap and continues down the drainage pipe.