From supply lines to wastewater disposal pipes and all the fixtures in between, your plumbing is a complex system with a lot of critically important components. As a result, there are thousands of terms used in the plumbing industry that are not a part of the common lexicon. This glossary from your Mississauga plumber at Mr. Rooter Plumbing of Mississauga gives definitions for some of the most commonly used plumbing terms, so you'll know exactly what your plumber is talking about when you need repair, maintenance or installation services.

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ABS (Acrylonitrile Butadiene Styrene): Black plastic material that is used to make pipes for drain, waste and vent lines.

Access Panel: A small door, hatch or removable panel in a wall that gives access to plumbing components that are typically hidden in the wall, such as shutoff valves and drain stacks, so a plumber can reach them for repair and maintenance purposes without cutting a hole in the wall.

Aerator: A device that attaches to a faucet or is part of a faucet that mixes air with the water that it is released to reduce splashing.

Angle Stop: A shutoff valve located between a water supply line and plumbing fixture so water supply to that fixture can be cut off when the fixture needs maintenance or repairs.

Anode Rod: In conventional, tank-style water heaters, this sacrificial component is made from steel core wire wrapped in aluminum, magnesium or zinc. Anode rods protect the metal lining inside a water heater tank from corrosion, and they wear out rapidly so they must be replaced regularly to stay effective.


Backwater Valve: A valve on a sewer line that prevents sewage from reversing directions and traveling into a building.

Ballcock: A valve attached to a ball-shaped float that controls the flow of water from a supply line into a toilet tank. The valve opens and refills the tank when the toilet flush lever is pressed, and closes once the float reaches the top of the tank to avoid overfilling. It is sometimes referred to as a float valve or ball tap.

Bends: A generic term that applies to elbows, or bent pipe connectors that allow a run of pipe to turn in a different direction. Bends can be made of any type of piping material.

Bidet: A ceramic fixture, typically located next to a toilet, with a water faucet and bowl that a person can sit on to wash up after using their toilet. Bidets are used instead of or in combination with toilet paper in many countries.

Boiler: A heating system that uses pipes and radiator units to convey heated water through a closed system for the purposes of providing radiant heat to a building.

BTU (British Thermal Unit): A measurement of thermal energy that represents the amount of heat necessary to raise the temperature of one pound of water by one degree Fahrenheit.


Cesspool: An underground pit where drainage system discharge is dumped. It retains solid organic material and allows liquids to seep through.

Cistern: A large container buried underground to collect and store rainwater.

Cleanout: An access point located at a convenient place in a drainage line to make it easier to clear a blockage with drain cleaning equipment.

Compression Fitting: A pipe connection that joins two pipes or tubes together without the need to solder them. An effective seal is created with sleeves, nuts, gaskets and ferrules inside the fitting.

Copper: An elemental metal represented by Cu on the Periodic Table of Elements. It is one of the alloys used to make brass, which is a common material for plumbing system components such as fittings and faucets.


Dam: A seal formed by water in a trapway to regulate the level of water in a toilet bowl.

Discharge Tube: An outlet tube that serves to connect a sump pump or disposal to a drain line.

Dope: Lubricant applied to a threaded fitting to make the pipe joint pressure tight and impervious to leaks.

Duo Valve: A washing machine valve with a single on/off lever that provides hot or cold water to the machine as needed.


Effluent: Liquid waste in a septic tank that is potentially hazardous.

Energy Star: A program jointly operated by the U.S. Department of Energy and the U.S. Environmental Protection Agency that rates and certifies products, such as plumbing-related fixtures and appliances like hot water heaters and dishwashers, that meet certain energy efficiency standards.

Escutcheon: A protective or ornamental flange that covers the gap where a faucet goes into a fixture or the wall.

Expansion Tank: A tank installed on a closed hot water line to negate excessive pressure by giving the hot water extra space to expand into.


Ferrule: A threaded ring made of copper or soft brass. In plumbing, ferrules are a part of compression fittings that exist to make the connection watertight. Compression ring bushing is another term for the ferrule.

Flush Valve: A valve located at the bottom of a toilet tank. When a toilet is flushed, the flush valve opens to allow water from the toilet tank to enter the toilet bowl via the rim holes. It is also referred to as a toilet flapper.

French Drain: An outdoor drain channel that is set into the ground and covered with rocks or other loose material that allows water to seep through to the drainage channel.


Green Plumbing: Plumbing components or practices that promote the conservation of water or electricity, such as low-flush toilets or tankless hot water heaters.

Groundwater: Naturally occurring water in the soil that comes from rain, snowmelt and other sources. In places with excessive groundwater, it can be forced up to ground level to form springs, wetlands and other water-related geographical features.


Hard Water: Water with high concentrations of dissolved minerals such as calcium and magnesium. While hard water is typically potable, it can cause problems for a plumbing system because mineral deposits build up over time inside pipes, fixtures, appliances and other parts of your system.

Head: 1. A measure of the water pressure caused by gravity—70.4 centimeters of height results in one pound of head. 2. A slang term for toilet.

Hose BibbAn indoor or outdoor valved water fitting that attaches to a hose, such as a garden hose or washing machine supply line.

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


Inside Diameter (ID): The diameter of the inside opening of a pipe, not counting the pipe walls.

Isolation Valve: A shutoff valve that allows a plumber to stop water flow to a section of a building or a major plumbing component like a house pump so they can do maintenance and repair work on that area or part without shutting off the water supply to the rest of the building.


Lavatory (Lav): In the plumbing industry, this term refers specifically to a bathroom sink. It's also an old-fashioned term that a layperson would typically use synonymously with water closet to refer to the entire bathroom.

Leader: Part of a rainwater disposal system that carries rainwater from the roof or horizontal gutter system to the ground or an underground drainage pipe. It is also referred to as a leader pipe or downspout.

Litres Per Flush (LPF): A measure of the total volume of water required to complete a flush cycle in a toilet or urinal, expressed in gallons.

Litres Per Minute (LPM): A measure of the rate at which water moves through a fitting or fixture, expressed by the number of gallons coming out of the fitting or fixture over the course of one minute at a given water pressure.

Liquid Waste: Liquid discharged from a plumbing fixture that does not contain human or animal waste.


Manifold: 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.

Master Plumber: A professional who has earned the highest designation level for a plumber. Master plumbers usually have at least ten years of experience, but many have been working as plumbers for much longer. They must complete an apprenticeship, become a journeyman plumber and earn their master plumber license to receive this designation, and they may choose to specialize in one type of plumbing.

Mixing Valve: A plumbing valve that delivers a certain temperature of water by mixing the correct ratios of hot and cold water.


Negative Pressure: Pressure that is lower than atmospheric. It can induce a partial vacuum in a pipe system that can siphon non-potable liquid into water supply lines.

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


Outside Diameter (OD): The diameter of a pipe from the outside edge, including the pipe walls.

Ovality: The difference between the widest outside diameter and the narrowest outside diameter on a given pipe or tube. The calculation to determine ovality is maximum outside diameter minus minimum outside diameter.


Peak Hour Demand: The time of day when the demand for hot water in a building, city or region is at its highest point. It is generally considered to be one-third of the overall average daily demand.

Potable Water: Fresh water that is safe to use for drinking, cooking, bathing and other household purposes.

pH (Potential Hydrogen): A measure of the acidity or alkalinity of a solution on a logarithmic scale where seven is neutral and higher values indicate the solution is more alkaline, while lower values indicate it's more acidic.

Pressure-Reducing Valve (PRV): A device that regulates water pressure to keep it consistent for home use when installed on main water supply lines. It is sometimes referred to as a pressure regulator.


Rated Storage Volume: The volume of water that a storage tank can hold, as rated by the manufacturer of the tank.

Rim Holes: A series of holes or small slats under the toilet bowl through which water pours into the bowl from the tank, rinsing away debris or liquids that are clinging to the side of the bowl.

Rough-In: A plumbing or electrical fixture or appliance that has been set in place but is not yet hooked up to supply and disposal lines.


Saddle Valve: A valve that provides a low volume, low-pressure water stream to appliances including ice makers or humidifiers.

Sediment: Particles of debris such as rust, dirt, mineral deposits and other substances that settle at the bottom of a hot water tank and can block water from exiting the tank.

Sewage: Wastewater and human waste that is transported through sewer systems for treatment and disposal.

Sewer Line: A disposal pipe that transports wastewater and human waste away from a building and deposits it in the city sewer or a septic system.

Supply Line: A metal or plastic pipe that carries potable water from the main line into fixtures and appliances.


Touchless Faucet: A handleless faucet that is motion activated by infrared so it can be operated by someone with dirty or occupied hands.

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.


ULF (Ultra Low Flush): A toilet that uses less than 6 litres (1.6 gallons) per flush to conserve water.

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

Usable Storage: The volume of hot water that can be removed from a water heater tank before the temperature is lowered to the point where it is no longer hot.


Wastewater: Water that has been used for a purpose such as cleaning, bathing or other purposes in domestic, commercial and industrial applications.

Water Hammer: A pressure surge that occurs when a fluid in motion is forced to stop or change direction suddenly. Water hammer causes pipes to vibrate and make banging or thumping noises. It can also cause more serious issues like pipeline collapse and leaky fittings.


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.

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