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Plumbing Terminology
Extensive Online Plumbing Dictionary

Click on any letter of the term you would like to find

Computer Aided Design.

Calcium Carbonate:
A white precipitate that forms in water lines, water heaters and boilers in hard water areas; also known as scale. Can be found in nature, also known as limestone.

Calcium Hypochlorite:
Extract the matter adsorbed from a stream of water by activated carbon, and then extracted from the activated carbon with chloroform, using a specific standardized procedure; a measure of the organic matter in water.

Calcium Magnesium:
Two of the principal elements that, when dissolved, make water hard. Their presence contributes to the formation of scale and insoluble soap curds.

Capacity (1):
Pumps - The flow rate in gallons per minute or liters per minute.

Capacity (2):
Water Softeners/Conditioners - Quantity of undesirable matter that can be removed by a water conditioner under standard test conditions. For ion exchange water softeners, this is expressed in grains of hardness removal between regenerations and is related to a pound of salt used.

Capacity (3):
Water Filters - For filters, capacity may be expressed in the length of time or total gallons delivered between servicing..

Capacity (4):
Water Heaters - The size in gallons of water of the storage tank.

Carbon Dioxide:
A gas present in the atmosphere, formed by the decay of organic matter; the gas in carbonated beverages; dissolved in water it forms carbonic acid.

Carbonate Alkalinity:
Alkalinity due to the presence of the carbonate ion.

Carbonate Hardness:
Water hardness due to the presence of calcium and magnesium carbonates and bicarbonates in water; the smaller of the total hardness and the total alkalinity.

In a pump, where a reduction of hydrocarbons result in the formation of carbon residue that will interfere with the movement of a mechanical seal. Often called coking.

Typically refers to a valve cartridge. It is a single-piece unit that replaces the use of separate seats, stems, and seals for water-flow control.

Carved Glass:
An artistic form of sandblasting that creates a multi-dimensional effect through the carrying depth of the design pattern.

A tubular structure intended to be watertight installed in the excavated or drilled hole to maintain the well opening and to prevent ground water from entering the well.

Cast Iron:
Heavy metal covered with a porcelain enamel coating formed by casting on molds to make fixtures such as sinks, tubs and lavatories.

Catch Basin:
Large underground container, with a grate on the top, for collection of storm water un-off. It catches or collects dirt and other debris and prevents them from polluting streams and lakes.

A negatively charged electrode.

A positively charged ion in an electrolyte solution, attracted to the cathode by a difference in electrical potential.

The tendency of any substance to burn or destroy animal flesh or tissue. The term is usually applied to strong bases.

Caustic Soda:
The common name for sodium hydroxide.

The vacuum created when the discharge capacity of the pump exceeds the replacement in the suction line. This causes bubbling and vibrations that can damage the pump if they occur over an extended period.

Certified Bathroom Designer.

Copper to copper soldered.

Celcon Nut:
Connectors used to hand-tighten faucets to lavatory from underside of lavatory.

A style of bathroom lavatory faucet that has a combined spout and handles. Center of handles are typically 4" apart. Also a single handle faucet installed on 4" center-to-center faucet holes.

Bathroom faucet which installs into fixture holes set 4" apart like a centerset faucet, but with the waterway between the two handles and the spout concealed below the lavatory deck.

Centrifugal Pump:
A pump that moves water by centrifugal force developed by rapid rotation of an impeller. As the rotating impeller whirls the water around, centrifugal force builds up pressure forcing the water through the discharge outlet.

Ceramic Cartridge:
A self-contained cartridge housing two ceramic discs. Full-on / full-off with 1/4 turn of the handle.

Cubic Feet Per Minute.

Certified Graduate Remodeler.

Chain Wrench:
An adjustable wrench in which a chain is used for gripping. Commonly used on large pipes.

Beveled end, usually done on pipe prior to threading.

Check Stop:
Shut-off valve used with tub/shower faucet that is activated by turning a slotted stem with a screwdriver. Also known as a "screwdriver stop" or a "service stop".

Check Valve:
A type of back flow preventer installed in a pipe that allows water to flow in only one direction.

A material made from a clay and water mixture, coated with liquid glaze and fired under extremely high temperature to form a hard, scratch and stain-resistant surface.

A gas, C2, widely used in the disinfection of water and an oxidizing agent for organic matter, iron, etc.

Cast Iron.

Circuit Vent:
Plumbing drainage system vertical vent which is run from the last two traps on a horizontal drain line to the main vent stack of a building drainage system.

Rainwater storage tank, often underground.

Clamp Straps:
Straps used to hold or support pipes.

Cleanout Plug:
A plug in a trap or drain pipe that provides access for the purpose of clearing an obstruction.

A U-shaped piece of metal with holes in the ends through which a pin is run to attach to pipes.

Clevis Hanger:
A type of pipe hanger with a swivel yoke supported at the top by an adjustable vertical rod. This yoke bolts to pins holding a U-strap of metal that supports the pipe

Clevis Insulator:
A clevis hanger with an insulating bushing where the vertical rod bolts to the yoke. Most often used with roller hangers and electrical conduit.

Close Coupled:
A toilet with a separate tank and bowl, secured to each other, and with a separate tank cover. Also known as a two-piece toilet.

Close Nipple:
Short lengths of pipe that are threaded on both ends. The threads are so close together they almost join in the center.

Closed System:
A system where the incoming cold water supply has a device that will not allow water to expand when heated.


Closet Auger:
A flexible rod with a curved end used to access the toilets built-in trap and remove clogs.

Closet Bend:
A curved fitting mounted immediately below the toilet that connects the closet flange to the toilet drain. The only fitting in plumbing where the fitting can legally reduce from 4" to 3". But a 3" long sweep 90° can also be used as a closet bend.

Closet Flange:
Component used to connect outlet of water closet to the drainage waste vent (DWV) system and to mount the fixture to the floor.

Closet Riser:
Flexible supply tube with flat end used to make the final supply connection to ballcock (toilet fill valve).

Closet Seat:
Toilet seat. A rim placed over a toilet as a seating surface.

Closet Sweep:
A curved, long radius 90° fitting, mounted immediately below the toilet that connects the closet flange to the toilet drain. Also known as a closet bend.

Closet Tube:
A water supply tube used for toilets.


A material such as alum, which will form a gelatinous precipitate in water, and cause the agglomeration of finely divide particles into larger particles which can then be removed by settling and/or filtration.

Coagulant Aid:
A material which is not a coagulant, but which improves the effectiveness of a coagulant, often by forming larger or heavier particles, speeding the reactions, or permitting reduced coagulant dosage.

The process in which very small, finely divided solid particles, often colloidal in nature, are agglomerated into larger particles.

A faucet or valve for regulating the flow of water.

Cockhole Cover:
A round cover-plate or disk installed on a sink to cover an unused faucet hole.

Coil Spring Tube Bender:
A flexible heavy-wire coil, which, when slipped over copper tubing, allows it to be bent without crimping.

In a pump, where a reduction of hydrocarbons result in the formation of carbon residue that will interfere with the movement of a mechanical seal. Also referred to as carbonizing.

Cold Drawn:
Pipe or tubing that's pulled through a die to reduce diameter and wall. Produces closer tolerances and higher strength.

Cold Vapor:
Method to test water for the presence of mercury.

Cold Venting:
Also called "Power Venting". Cold venting is where a blower is used to force the byproducts of a furnace or water heater through PVC pipes to outside.

Coliform Bacteria:
Non-pathogenic microorganisms used in testing water to indicate the presence of pathogenic bacteria.

A galvanized sheet metal restricting device used in conjunction with plastic pipe. Its function is to direct and control the intumescent action of the fire stopping material.

very finely divided solid particles that remain suspended in a solution; the removal of colloidal particles usually requires coagulation.

Combined Sewer:
A sewer system that carries both sanitary waste and storm water runoff.

Combustion Chamber:
The location where combustion takes place.

Combustion Gases:
Gases released when a gaseous, liquid, or solid fuel reacts at an elevated level that needs to be vented with gas or oil-fired water heaters.

Commercial Heater:
Water heaters used for more than a single-family dwelling.

Commercial Water Use:
Water for motels, hotels, restaurants, office buildings, other commercial facilities, and institutions.


Common Vent:
Building drain system vertical vent which connects two or more fixture branches on the same level.

An abbreviation for (brass) compression fittings. Normally used to describe a fitting when one side is not compression. Example: 3/8" comp x 3/8" mipt

Compensated Hardness:
A calculated value based on the total hardness, the magnesium to calcium ratio, and the sodium concentration of water. It is used to correct for the reductions in hardness removal capacity caused by these factors in cation exchange water.

Composite sinks made from high-tech, high-strength, color-impregnated that resists chipping and scratching.

Composting Toilet:
A self-contained toilet that use the process of aerobic decomposition to break down feces into humus and odorless gases.

Compression Fitting:
A kind of tubing or pipe connection where a nut and a sleeve or ferrule is placed over a copper or plastic tube and is compressed tightly around the tube as the nut is tightened forming a positive grip and seal without soldering.

Compression Valve:
Term used to describe a faucet valve in which the flow of water is shut off by means of a washer that is forced down onto its seat.

Concealed Arm Carrier:
Used to securely mount a wall mount lavatory. Unlike a hanger which only supports the lavatory where it meets the wall, the carrier has long arms onto which the lavatory slides.

Water vapor that separates from products of combustion due to a reduction in heating surface temperatures to below the dew point of surrounding air. Water formed when water vapor forms in a gas combustion loses heat before it passed out the venting system.

In water conditioning, the readiness of water to carry electricity. The unit of measure for conductance is the mo; it is used to approximate the dissolved solids content of water.

The quality or power to carry electrical current in water, the conductivity is related to the concentration of ions capable of carrying electrical current.

Tube that houses electrical wiring.

Conduit Clamp:
A screw-down, U-shaped spring clamp formed out of a band of metal used to hold conduit pipe.

Conical Sponge Washer:
Sealing washer on urinal between outlet connection at the wall and the china to make a watertight seal.

Connecting Rod:
Also known as lift rod. The rod that caused the drain to close when lifted.

Console Lav / Console Table:
A table-like fixture with an integral lavatory. The back is fixed to a wall and the front is supported by brackets or legs.

Consumptive Water Use:
Total amount of water used by vegetation, mans activities, and evaporation of surface water.

Countertop Sink:
Style of lavatory which drops in or adapts to a cutout in the countertop.

Continuous Feed:
Wall switch activated type of garbage disposer in which garbage is fed into the unit while running.

Continuous Hinge Door:
A shower door that has a full-length continuous metal hinge on the side of the door.

Conventional Vent:
A flue piped to exit vertically out through the roof of a building. Allows vapor or air to escape to open air.

C.O. Plug:
Lavatory drain with separate removable (pull out) plug, but without an overflow opening.

Corporation Cock:
A stopcock screwed into the street water main to provide the house service connection.

Corporation Stop:
The stop connected to the water main, usually made of brass and can be connected to the main with a special tool without shutting off the municipal supply.

The disintegration of a metal by electrochemical means.

Corrosive Water:
A water condition of low pH that can corrode metal pipes, pool fixtures, and pumps.

Straight, sleeve-like fitting with female connections at both ends.

A short fitting used to join two pieces of pipe.

Polished Chrome.

CPE Solvent:
Chlorinated Polyethylene. A melting agent to form seams in shower pan liners.

Chlorinated Polyvinyl Chloride. Rigid plastic pipe used in water supply systems, where code permits. Withstands high temperatures.

Crocus Cloth:
Finer than sandpaper grit on a cloth backing.

Any connection or situation that may allow wastewater to enter the supply system.

IF tub or shower outlets are completely closed but the main valve(s) is/are left open, it will cause the hot and cold to mix potentially creating a scalding condition when one of the outlets is reopened.

Crown-vented Trap:
An air admittance valve attached to a drainpipe, protected by a check valve, designed to equalize pressure in the drain line and to protect the trap seal.

Crown Weir:
The interior projection in the outlet side of a P-trap to aid in maintaining the water seal in the trap.

Crows Foot:
A PVC tee with twin outlets at right angles off the main.

An intestinal protozoan parasite resistant to chlorine. It infects the intestines and causes diarrhea, nausea and cramps. Can be removed through filtration.

Corrugated Stainless Steel Tubing. Also known as TracPipe, it has a polyethylene jacket.

Copper Tube Size. Refers to outside diameter; Used to size certain fittings and hangers.

Cubic Foot of Gas:
the amount of gas that will occupy one cubic foot at a temperature of 60°F, and under a pressure equivalent to that of 30 inches of mercury.

A pipe-like construction of concrete that passes under a road to allow drainage.

A raised edge or border of a shower.

Curb Cock:
Shutoff valve normally used with water meters set between the meter and the building.

the movement of electrons through a conductor, measured in amperes.

Curtain Drain:
A ditch sometimes filled with gravel or drainage tile which diverts storm water away from a structure.

Cut Lengths:
Pipe cut to a specific length as ordered.

Continuous Weld. A method of producing a small diameter pipe.

Copper Water Tube

The number of times per second that a conductor of alternating current reverses polarity.

Cycle Time:
The time beginning at the instant a toilet flush lever is actuated until the instant the water supply shuts off, completing the flush cycle.

A group of chlorine-resistant microorganisms that when ingested can cause gastrointestinal illness.