Professional Plumbing Glossary


ABS (Acrylonitrile Butadiene Styrene): A black plastic pipe that is used for waste, drain, and vent lines.

Access Panel: A door, panel, or sheet of plywood that can be removed for easy access to drains, shut-off valves, and other plumbing parts that need occasional maintenance.

Aerator: A faucet component that assists in water conservation. It works by aerating water as it exits a faucet to reduce total water output while still maintaining the same perceptible flow rate.

Angle Stop: An emergency shut-off valve located under plumbing fixtures and water-related appliances; a valve that stops water flow in a specific fixture or appliance without disrupting water services for the rest of the building.

Anode Rod: A sacrificial component of conventional water heaters; a steel core wire wrapped in aluminum, magnesium, or zinc. Anode rods are installed inside water heaters to protect the metal lining inside their tank from corrosion, and they must be replaced regularly to stay effective.

Anti-Scald Valve: A mechanism that controls the hot and cold water pressure balance in a shower to avoid releasing scalding hot water in the event of a sudden pressure drop.

Anti-Siphon Valve: A backflow prevention device used in sprinkler systems to prevent irrigation water from contaminating a connected potable water supply.


Backflow Prevention Device: A system or component—such as a backwater valve—designed to prevent water contamination by stopping liquids from flowing backwards into your main supply lines.

Backwater Valve: A specific type of backflow prevention device that prevents wastewater from backing-up into private buildings from public sewer lines.

Ballcock: Also called a float valve or balltap, this is a valve attached to a ball-shaped float that controls the flow of water from a supply line into a toilet tank. When the toilet is flushed, the valve opens and refills the tank, stopping once the float reaches the top of the tank.

Balling Up: A welding term for when globules of molten brazing filler metal or flux form because base metals were not wetted.

Bleed: A method used to remove excess air from a pipe by opening a connected valve at one end of the pipe.

Branch Vent: A vent pipe that connects multiple vents (or one individual vent) to a vent stack.

BTU (British Thermal Unit): A unit of measurement for how much heat is required to raise the temperature of one pound of water by one degree Fahrenheit. BTU is used to measure the efficiency of heating systems.


Centerset: A bathroom faucet style in which the spout and faucet handles are combined in one unit, or a single-handle faucet installed on four-inch center faucet holes (see: widespread).

Circuit Vent: A single common vent connected to a horizontal branch line and used for as many as eight fixtures.

Cleanout Plug: A metal or plastic plug in a drain pipe, vent, or trap that can be removed to provide access to clear out a blockage.

Closet Bend: A curved fitting that connects a toilet to its drain via a closet flange.

Closet Flange (Floor Flange): A circular piece of metal, PVC, or rubber that secures a toilet to the floor and connects to the drain pipe.

Compression Fitting: A pipe connection used in plumbing to join two tubes or pipes together without soldering them. Compression fittings use nuts, sleeves, gaskets, and ferrules to create an effective seal.


Dam: The barrier in a toilet trapway that regulates the water level in the toilet bowl.

Diaphragm: A flexible membrane inside a valve that controls the flow of liquids or gases by changing the valve to an open or closed position.

Dip Tube: A plastic tube that fits into a water heater's cold water inlet and extends to the bottom of the tank, ejecting cold water into the tank at the bottom near the burners.

Dope: Pipe dope is lubricant applied to a threaded fitting to make the pipe joint pressure tight and leakproof.

Drip Leg: Often called a sediment trap, this is a pipe on the lower segment of a gas line that collects condensation and debris in a capped-off section.


Effluent: Liquid waste in a septic system.

Energy Factor (EF): A water heater rating that measures efficiency, recovery, energy input, and stand-by loss.

Expansion Tank: A water heater tank capable of negating excess pressure from thermal expansion.


Ferrule: A threaded ring made of soft brass or copper that goes inside a compression fitting to make the connection watertight. Ferrules are sometimes called compression ring bushings.

Fixture: 1. A device or system that provides water access, such as a faucet, bathtub, or shower.
2. Any part of a plumbing system that is responsible for removing waste, such as a toilet or drain.

Flapper Valve: Located at the bottom of a toilet tank, this is the component that allows water to flow from the tank to the bowl when the toilet is flushed.

Floor Drain: Any drain that is set in a floor, such as inside a shower or in a laundry room, to drain water off the floor surface.

Flow Rate: The volume of fluid that passes through a plumbing system in a specific amount of time, also known as volumetric flow rate or volume velocity.

Flush Valve (Flushometer): The valve that opens when the flush lever is pushed to allow water to flow from the tank to the toilet bowl, and which closes when the bowl is full.

Flux: A material that prevents oxidation and assists with the fusion process when applied to copper pipes and fittings before soldering.


GPF (Gallons Per Flush): The volume of water that a toilet uses when it is flushed, which is also measured in LPF (litres per flush).

Gravity-Operated Toilet: A toilet that uses the natural downward pressure of water flowing from a tank to flush its contents; the most common type of toilet found in residences.

Grey Water: Domestic wastewater in residences and office buildings from sinks, showers, bathtubs, and other sources that are not contaminated with human waste. Grey water (“gray” water in the United States) can be recycled for non-potable purposes.

Groundwater: Naturally occurring water beneath the surface of the Earth. It is recharged from natural sources such as rain, and can emerge from the ground to form springs, wetlands, and other geographical features.


Hose Bibb: 1. A fixture commonly referred to as an outdoor faucet, spigot, or garden faucet; an exterior faucet used to connect a garden hose with the water supply.
2. A hose or tube that supplies water to washing machines.

Hubless: Also called a no-hub, this is a drain pipe made of cast iron with neoprene clamps and gaskets.

Hydronic Heating: A heating system that uses hot water to supply radiant heat, such as a boiler.


Johnny Bolts: Used to secure a toilet to a closet flange.


Lavatory (Lav): 1. A bathroom sink fixture comprising a basin or bowl, faucet, faucet handles, and a drain.
2. A bathroom.


Main: The main pipe connecting interior and exterior plumbing systems; a sewer line that carries wastewater and sewage to public sewers or a septic tank, or a water line that carries fresh water into private buildings.

Manifold: A section of pipe with built-in ports to allow hot and cold water to flow to various fixtures and appliances, such as sinks, bathtubs, showers, dishwashers, and laundry washing machines.

Mechanicals: 1. Systems that use electrical, plumbing, and heating and cooling components to make a building livable.
2. The moving parts of specific fixtures and appliances such as a furnace or water heater.


Nipple: A short piece of pipe that is used to create a water seal and connect a pipe to threaded fittings, valves, or equipment.

NPT (National Pipe Thread): The most common standardized thread type used for pipe connections in Canada and the United States.


O-Ring: A small, flexible, ring used to create a watertight seal in plumbing fixtures. O-rings need to be replaced regularly; deteriorated O-rings are a common cause of dripping faucets.


Peak Hour Demand: The time of day when there is typically the greatest demand for hot water.

Pipe Threads: Spiraled ridges along the connecting parts of a pipe that allow them to be screwed together and interlock tightly.

Pitch (Fall): The slope of a pipe that allows for gravity-based water flow.

Preheating: A welding term that refers to the application of heat to a base material before soldering or brazing.

Pressure Regulator: A system installed on main water supply lines to keep water pressure consistent for home use. A pressure regulator could also be referred to as a pressure reducing valve or PRV.

Pressure Tank: The device used in well water systems to help pump water out of the well and provide water under pressure when the pump is not in operation. Pressure tanks also provide a reserve supply of water for periods of high demand.

PSI (Pound-Force Per Square Inch): A measurement of water pressure. The pressure produced by a typical faucet ranges from about 40 to 60 PSI.

PVC (Polyvinyl Chloride): In plumbing, PVC is a rigid plastic pipe, usually white or light beige, that is used for non-pressurized vent, drainage, and waste systems.


Rated Storage Volume: The exact amount of water stored in a water heater tank, in gallons, as specified by the manufacturer.

Reamer: A tool used to remove metal burrs from the interior of pipes, or from holes that have been drilled in metal.

Refill Tube: A component that maintains the water level in a toilet bowl by refilling it from the tank as needed. Refill tubes must be located above siphon tubes to operate correctly.

Rim Holes: The holes underneath the rim of a toilet bowl through which water pours into the bowl from the tank, creating a rinsing effect across the interior surface of the toilet bowl. 


Saddle Valve: A valve that provides a low volume, low pressure stream of water to appliances such as humidifiers and ice makers.

Sediment: Debris such as rust, dirt, and other particles that settle at the bottom of a water tank.

Soil Stack: The drain line that connects to all branch lines and carries waste to a building’s sewer main; this is often the biggest vertical drain line in a building.

Solder: 1. The metal alloy that creates a fused joint between metal pieces when melted.
2. The act of applying solder to a joint.

Spigot: 1. The end of a PVC or CPVC fitting that is the same size as the pipe, which is used to connect a fitting to another fitting inside a socket.
2. The plain end of a cast-iron pipe.

Stack: A vertical drain line in a waste, drain, and vent system that extends upward one or more storeys.

Sewage: Wastewater that comes from toilets, or any water contaminated with human waste.


T & P Valve (Temperature & Pressure Relief Valve: A safety device on water heaters that is designed to release excess pressure and heat from inside the tank.

Thermostatic Valve: A valve with a thermal actuator that regulates temperature and pressure fluctuations by adjusting the ratio of cold to hot water to maintain a desired temperature setting.

TPI (Threads Per Inch): A measurement of the number of pipe threads on a fastener. Metric fasteners use a similar unit of measurement called thread pitch, which measures the distance between individual threads.

Touchless Faucet: A faucet without handles that is motion activated by infrared. Touchless faucets are mostly used for commercial applications, though they can be found in some homes.


ULF (Ultra Low Flush): A term used for toilets that have a GPF (gallons per flush) rating of 1.6 or lower.

Union: A plumbing fitting that joins sections of pipe together so they can be decoupled without cutting through the pipe.

Usable Storage: The amount of hot water in a water heater tank that can be used before the temperature drops too low to be considered hot.


Valve Seat: The stationary part of a valve that prevents water flow when it comes in contact with the moveable part of the valve.

Vent Stack: A system that regulates air pressure to prevent a vacuum from forming in a plumbing system, which could cause slow drainage or prevent water from draining at all. Vent stacks are also called vent pipes or plumbing system air pipes.


Wastewater: Dirty water from toilets, sinks, bathtubs, other drains, and pipes that transport waste through plumbing systems. Grey water and sewage are both different types of wastewater.

Water Closet: An old-fashioned term for toilets and bathrooms that is commonly noted on plumbing schematics as WC.

Water Hammer: Loud banging noises that come from pipes when water valves are opened or closed. Water hammer appears because of sudden changes in pressure, and it’s often caused by fluid in a vent stack, although there are other possible causes.

Wax Ring: A ring that fits between the hole in the bottom of a toilet fixture and the flange that connects to the drain pipe to form a pliable seal between the two.

Widespread: A type of bathroom faucet in which the spout and handles are separate from each other, usually measuring eight inches from center of handle to handle (see: centerset).


Yoke Vent: A vent pipe that connects from a vertical waste stack or soil stack to a raised location in order to prevent pressure changes in the stack pipe.