Glossary of Plumbing Terms

As the premier family-owned plumbing company in the Indianapolis area for the past three decades, Hamm & Sons Plumbing values transparency in our practices. That includes ensuring our customers understand exactly what we mean when the occasional technical plumbing term comes up during our discussions. We want to provide the information you need to confidently make informed decisions regarding the services inside of your home or business. Though it is our practice to always describe plumbing matters in easy to understand terms, there are times when technical accuracy is important.

This comprehensive list of plumbing terms is a great tool to help you learn more about the inner workings of one of your home or businesses’ most important systems.

plumbing terms


Acrylonitrile Butadiene Styrene (ABS)

Type of rigid black plastic pipe used for drainage, waste disposal and vent lines

Absorption Field (Disposal Field, Leach Field)

A series of trenches engineered to receive effluent from the septic tank and disperse it in a manner that allows the flow to be distributed uniformly into natural soil

Access Panel

An opening in a wall or ceiling near a fixture that provides access to work on plumbing or electrical systems


A fitting that joins two different kinds of pipes together, such as threaded to non-threaded or ABS to PVC


A device attached to a faucet that mixes air into the flowing water, controlling the flow to reduce splashing

Air Admittance Valve

A valve that allows air to enter the pipe to equalize pressure, preserving the seal of water in the fixture trap. An air admittance valve replaces a traditional vent.

Air Check Valve

A device that allows water to pass through it but prevents air from bleeding out of the tank


The ability to survive without oxygen; e.g. some types of microorganisms that break down waste in a septic system

Angle Stop

A shutoff valve between the water supply and a plumbing fixture; also used to reverse the direction of water flow

Anode Rod

A degradable metal rod made from a steel wire core wrapped in magnesium or aluminum. The rod is inserted into a water tank to attract the ions that would otherwise cause the tank to rust. The protection provided by the anode rod only occurs while the rod is degrading; when it has fully degraded, it must be replaced to continue protecting the water tank.


Back Pressure

Pressure that resists the flow of fluid in a piping system caused by obstructions such as welds that weren’t ground flush to the pipe or bends in the pipe. These obstructions can create a pressure drop resulting in reduced water flow.


Overflow of a plumbing fixture due to drain blockage

Backwater Valve

A valve that prevents sewage from backing up into the home through water drainage systems, such as showers or sinks

Balancing Valve

A water heater valve that controls water flow, ensuring the proper distribution of the heat flow in the system

Ball Check Valve

A valve that uses a ball to seal against a seat to stop flow in one direction


Also referred to as a balltap or float valve, the ballcock is a mechanism that controls the flow of water in a flush toilet tank. When the toilet is flushed, the circular float will drop and open the ballcock, allowing water to fill the tank. As the water rises, the float rises and shuts the ballcock to prevent overflow and backflow.

Ball Passage

This refers to the size of ball that can pass through the trapway of a toilet. In general, the trap size will be 1/8" larger than the maximum size ball that can pass through it.


Refers to the absence or minimalism of bottom tracks in handicap-accessible showers and baths


A receptacle to hold water discharge from a tap, i.e. a sink or bathtub

Basin Wrench

A long-handled wrench with swivel-mounted jaws designed to reach and handle nuts and faucet fasteners

Beehive Strainer

A strainer inserted into a urinal to prevent debris from entering the drain

Biochemical Oxygen Demand (BOD)

The measurement of the amount of dissolved oxygen that must be present in water for microorganisms to break down organic material present in the water. BOD is used as a parameter of the potency of sewage and wastewater. Insufficient oxygen amounts can result in an environment in which microorganisms cannot thrive or survive.

Black Pipe

Lacquer-coated cast iron pipe


To rid a pipe of excess air by opening a valve at one end of the pipe

Blowbag (Blowfish)

A rubber bladder fitted with a hose on one end and a nozzle on the other; the bladder is inserted into a clogged pipe and filled with water, causing the bladder to expand to grip the sides of the pipe. The device then releases sonic bursts of water through the nozzle forcefully enough to clear obstructions in the pipe.


Using pressure to partially drain the water side of a boiler to remove foreign contaminants


A tank in which water is boiled; the resulting steam is used for heating or power


The top portion of a compression valve assembly. The bonnet holds the valve stem in place as it is tightened against the valve seat at the other end of the assembly and provides leakproof closure for the valve body.


The end of the pipe that is threaded on the inside (female)

Brackish Water

A nonpotable mix of salt (sea) water and fresh water


A strong solution of sodium chloride (salt) used in the regeneration of ion-exchange water softeners.

Braided Hose

Flexible connecting hose

Brake Horse Power (BHP)

The amount of horsepower being consumed by a pump. BHP is measured on a dynamometer.


Also referred to as a lateral line, a branch is any secondary portion of the drain system.

Branch Vent

A branch vent connects vents with a vent stack.

British Thermal Unit (BTU)

A unit of heat energy required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

Burst Pressure

The amount of pressure that a pipe or tube can handle before rupturing


A pipe fitting that has threading on both the inside and outside; used to join two pipes of different sizes

Butterfly Valve

A type of quarter-turn valve that allows water to flow through it when open, and stops the water flow when closed.


Calcium Carbonate (Hard Water Scale; Carbonate Hardness)

A solid white precipitate that forms in hard water lines, water heaters and boilers

Calcium Magnesium

Dissolved elements that make water ‘hard’ and contributes to the formation of calcium carbonate (hard water scale)

Catch Basin

A large underground container that collects stormwater runoff through a grate. The grate catches debris to prevent it from entering nearby bodies of water (lakes, streams)


A vacuum created by the discharge capacity of the pump exceeding the replacement in the suction line, causing damage the pump if not immediately rectified

Centrifugal Pump

A pump that forces water through the discharge outlet by centrifugal force

Check Stop (Screwdriver Stop; Service Stop)

Shower/bathtub shut-off valve used by turning a slotted stem with a screwdriver.

Check Valve (Ball Check Valve)

A valve that is installed on a pipe to allow water to flow in only one direction.

Cleanout Plug

Located in a trap or drain pipe, the cleanout plug provides access to the drain line for clearing out clogs or blockage in the pipe.

Closed System

A water system in which the incoming cold water supply is fitted with a device that will not allow water to expand when heated.

Closet (Commode)

Synonym for a toilet, also referred to as a water closet

Closet Auger

A flexible rod used to remove clogs from a toilet’s trap.

Closet Bend

A connector that connects the closet flange to the toilet drain.

Closet Flange

Used to anchor the closet bend to the floor, the closet flange is a ring that has closed bolts to secure the toilet in place.

Cold Vapor Atomic Absorption Spectrometry

A testing method for detecting mercury in water in which there is no vaporization step

Coliform Bacteria

Non-pathogenic microorganisms used to test water for the presence of pathogenic bacteria.



A flexible membrane that helps regulate water flow and buildup within a valve.

Dip Tube

A tube inserted into a water heater tank to send cold water to the bottom of the tank.

Direct Tap

A clamp that allows a branch line to be added to the main water line.

Drip Leg

Also referred to as a sediment trap, the drip leg is a pipe installed at the lower segment on a gas line. The capped-off section collects condensation and debris.

Dynamometer (dyno)

A device that measures both the torque and rotational speed of an engine to calculate its instantaneous power. The unit of measurement for the output is expressed in kW or bhp.



The liquid portion of septic system waste

Energy Factor (EF)

The overall efficiency rating of a water heater based on its efficiency, recovery, stand-by loss and energy input.


A protective flange or cover under the faucet handle that covers the fixture’s hole

Expansion Tank

A water heater tank designed to absorb excess pressure due to thermal expansion



The proper slope needed to create proper drainage in pipes

Feed Pump

A pump that supplies feed water to a boiler


Metal cap or cover used to create a tight compression fitting in two joined pipes

Fill Valve

Float-type shut-off valve designed to refill the toilet tank and bowl with water after flushing


A device that provides water or disposal, as in toilets, sinks and tubs/showers


A rib, collar or rim that strengthens or attaches sections of piping together

Flapper Valve (Flush Valve)

A valve in the toilet tank that connects the tank and toilet bowl; when opened, water is able to flow from the tank into the bowl

Flex Coupling

Rubber coupling used to join water or drainage pipes of differing materials, such as PVC to cast iron

Float Ball

The float ball is the plastic ball attached to the ballcock. The rise and fall of water in the tank is determined by the float ball’s placement.

Floor Flange (Closet Flange)

A cast iron, PVC, or metal ring that connects a toilet to the sewer line


A valve on a toilet that shuts off automatically after it detects a set amount of water flow

Foot Valve

A type of check valve located at the bottom of the pump’s suction pipe which opens to allow water in when the pump operates and closes to keep the water from flowing out when the pump shuts off



Flat piece of rubber used to provide a watertight seal between metal joints

Gate Valve

The gate valve, also known as a sluice valve, controls the flow of liquids in pipes by lifting a barrier (gate) out of the path of the fluid to facilitate the flow and lowering the gate to block the flow.

Globe Valve

A gate valve made of a movable plug or disc element and a stationary ring seat in a curved chamber

Gravity-Operated Toilet

A gravity-operated toilet relies on the downward pressure of water in a toilet tank to flush. Gravity-operated toilets often have ballcocks in their tank.

Gray water

Gray water is wastewater from fixtures such as sinks and tubs, but not toilets

Guide Arm (Float Arm)

A level that connects the flapper valve with the toilet handle; facilitates the control of water flow into and out of the toilet tank


Hard Water

Natural water containing impurities such as calcium or other dissolved solids; generally found in ranges from 100–250 ppm

High-Temperature Limit Stop (Anti-Scald Valve, Pressure Balancing Valve)

A mechanism that provides additional safety by disallowing the maximum temperature of flowing water to exceed a pre-set tolerance

Horizontal Branch

Lateral drain pipe that runs from a plumbing fixture to the waste stack Horizontal Run The distance liquid travels between the entry and exit points of a pipe.

Hose Bib

A hose bib is a common outdoor faucet.

Hydronic System

A heating or cooling system that uses water as the heat-transfer medium in a circulating loop.

Hydrostatic Pressure

The gravitational pressure exerted by a liquid increasing in proportion to the depth of the liquid from the surface due to the increasing weight of the fluid


In-line Pump

Small pump that uses centrifugal force to pump fluid through the line on which it is supported and mounted

Insert Fittings

Sleeve-like pipe fittings made of plastic, nylon or PVC that are equipped with rings or barbs for gripping; typically used by inserting into flexible rubber or plastic tubing as a means of connection

Instantaneous (Tankless) Water Heater

A type of water heater that heats water directly without the use of a storage tank by passing cold water through a gas- or electric-powered heat exchanger coil.


J Bend (Return Bend, P-Trap, U-Bend, S-Trap)

The curved pipe under a sink that keeps sewer gases from entering the home

Johnni-bolts (Closet bolts)

Bolts that are used to mount toilet bowls to the closet flange


Leader (Downspout)

A pipe designed to drain rainwater from the gutter, down the side of the building and out to the ground or sewer


Main Line

The main line supplies water from the water company’s meter at street level to the branch pipes around your home.

Maximum Contaminant Level (MCL)

The maximum level of a contaminant allowed in water by federal law, based on effects on human health and available testing and treatment methods

Mixing Valve

A valve that allows hot and cold water to mix in order to achieve a specified temperature



A short length of pipe, typically very tightly threaded on both ends, that connects couplings and other fittings.

Nipple Extractor

A tool used to unscrew sections of pipe

No Hub (Hubless) Pipe

A pipe with no threading; requires a special type of connector which connects two no hub pipes by butting the ends of the two pipes together and sealing them with a hub coupling


Not suitable for drinking



A unit of electrical resistance


Round rubber gasket designed to be seated in a groove and compressed during the joining of two or more lengths of pipe, creating a watertight seal at the interface

Outside Diameter (OD)

The outside diameter of a pipe



A small faucet for draining liquids or bleeding air pressure

Polybutylene (PB)

Flexible plastic tubing used in water supply systems


Safe to drink

Power Flush System

The power flush system compresses water to provide a pressurized flush. This system is often found in business and commercial settings.

Pressure Reducing Valve (PRV)

PRV, or pressure reducing valve, is a special valve that is installed directly on the main water line. The PRV constrains the amount of water entering from the water company’s supply to normalize water pressure for home use.


PVC pipes are sturdy plastic pipes that are used for drainage, waste and vent systems.


Raw Water

Untreated water


The reduction-oxidization potential of water. Redox indicates the ease at which chemical reactions take place in a tank; a high redox value is better than a low one.

Relief Valve

A valve that opens to relieve excess temperature

Rim Holes

A series of small holes around the inside rim of the toilet bowl from which water flows into the bowl Rough-In Installation of the drain, waste, vent and supply lines to prepare for finished plumbing fixtures


Saddle Valve

The saddle valve is a mounted pipe run by a clamping device. The saddle valve is used to make quick connections between low-demand devices.

Septic Tank

A small sewage treatment system that uses bacteria to decompose the waste inside the tank; typically used for homes with no connection to local sewage pipes.

Sewer Gas

Potentially combustible and toxic gases resulting from the decay of organic materials in the sewer system. Sewer gas is typically composed of hydrogen sulfide, ammonia, methane, carbon dioxide, sulfur dioxide and nitrous oxides.

Shock Load

Abnormally high rate of flow or concentration of pollutants received by a wastewater treatment facility which causes problems in the treatment processes. Shock loading creates the need to readjust procedural practices to return the process to normal.

Slip Joint

A connection made with compression fittings

Soft Water

Water that contains a low concentration of calcium and magnesium

Soil Stack

A water system’s largest vertical drain line to which all branch waste lines connect and that carries waste to the sewer line


The plain end of a cast-iron pipe, which is inserted into the bell end of the next pipe to create a watertight joint.

Straight Stop Valve

A straight shutoff valve used to close off water supply during repairs

Sump Pump

A sump pump is used in basements that flood often. The sump pump sits in a pit that accumulates the water, where it pushes the water outside the home.

Supply Line

A supply line is a metal or plastic line that carries water directly from the main line into a plumbing fixture.


T&P Valve or Temperature and Pressure Valve

The temperate and pressure relief valve is used to safely release excess heat or pressure in a water tank.


The tailpiece is a pipe that runs between a fixture and trap.

Thermostatic Valve

A valve that possesses an automatic temperature control feature. When water temperature fluctuates, the device, called a thermal actuator, adjusts the ratio of hot and cold to maintain the original temperature setting

Thread Seal Tape (PTFE Tape, Teflon Tape, Plumber's Tape)

A polytetrafluoroethylene (PTFE) film tape used for sealing pipe threads by providing lubrication to allow for a deeper seating of the threads; also helps to prevent the threads from seizing when being unscrewed.


The passage connecting the toilet bowl to a waste outlet

Trip Lever (Flush Handle, Actuating Arm, Guide Arm)

A lever attached to the flapper, which results in the toilet flushing when tripped.



A three-piece fitting that joins two sections of pipe, but allows them to be disconnected without cutting the pipe.


Valve Seat

The static part of a valve which allows water flow to stop when the moveable portion of the valve makes contact with the valve seat


A pipe that allows air into the drain system

Vent Header

A main vent pipe into which several vents connect, leading to the vent stack outside of the building

Vent Stack (Stink Pipe)

Outlet pipe that releases gas and odors outside the structure

Voral Tube

Flexible steel hose used for hand-held showerheads


Waste Arm

Drain extension pipe typically used to extend a sink drain into a wall

Waste Shoe

Bathtub drain assembly

Water Hammer

A loud noise caused by the vibration associated with water pipes being turned on or off

Water Hammer Arrestor

A device designed to absorb the hydraulic shock caused by water pipes being turned on or off

Working Pressure

The maximum permissible pressure of the water system



A brass, copper or other metal casting that holds both the hot and cold valves and the mixing chamber for the water.

Yoke Pipe Vise

A vise used to provide the strongest jaw-to-jaw grip for high torque applications such as threading.

Yoke Vent

A pipe that connects a soil or waste stack to a vent stack for the purpose of regulating pressure in the stacks

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