Plumbing Terms - Glossary of Plumbers Terminology

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Compression Fitting

A compression fitting is a kind of pipe or tubing connection where a nut and a sleeve (or ferrule) are placed over a copper pipe or plastic tube and is then compressed around the pipe or tube as the nut tightens, forming a positive grip, sealing the connection without any soldering. It is also a flexible connector that has a nut and gasket designed to attach directly to an SAE standard compression thread, without the use of a sleeve or ferrule.

Concentric reducer

A concentric reducer, also known as a tapered expansion joint, is a type of plumbing fitting that is used to connect two pipes or tubes that have a different inside diameter. Both the pipes need to share a common centerline or alignment to facilitate the flow of water or a substance.

Copper Type

The Copper Type refers to the type of copper that is normally used in pressure or water applications normally in residential construction type K or type L is preferable. The higher in letter the thinner the copper will be.


With coupling is meant a type of fitting with two female ends that receive the smaller ends of piping or tubing, making a connection. A mechanical device or part for joining two pipes together. When the two pipes have differnt sizes then the fitting may be called a reducing coupling or reducer, or an adapter. The term 'expander' is not used for a coupler that increases pipe size; instead 'reducer' is used.

Cross Fitting

A cross fitting has one inlet and three outlets, or three inlets and one outlet. Crosses are common in fire sprinkler systems, but not in plumbing due to their extra cost as compared to using two tee fittings. The three outlets should be named in order; left, middle , right.  For example 15-22-15

Disposal Field

With a disposal field is meant a series of trenches to which the effluent form the septic tank is conveyed. The disposal fields are designed and laid out in such a way that the flow from the septic will graduately be distributed into the natural soil that surrounds the disposal field.


A diverter is a three-way valve which splits up incoming water flow in multiple directions to other outlets. Tthe waterflow can be diverted from one outlet to another, or different inlets can be selected and sent to a common outlet. In the plumbing trade diverters are used in showers, tubs, bidets, and sinks.

Double Sanitary Tee

A double sanitary tee also know as a sanitary cross is a fitting that differs from a standard cross in that two of the ports have curved inlets. The fitting has been used in the past for connecting the drains of back to back fixtures (such as back to back bathroom sinks). Some current codes preclude the use of this fitting for that purpose. Instead a Double Fixture Fitting is required.

Drain Rod

A set of drain rods is plumbing equipment used to attempt to unblock drains and sewers. The set normally consists of several stiff, but flexible, rods, each approximately one metre long, which may be screwed together end-to-end. In addition the set usually has one or two unblocking tools, which may be a flat plate or an auger, which can be screwed onto one end.

The screwed together rods and tool are inserted into a drain or sewer from an access point, sometimes referred to as a rodding point or cleanout, and used to attempt to dislodge a blockage. Rodding is the act of using a drain rod.

Drum Trap

A drum trap is a plumbing fixture, which is cylindrical in shape, which retains water as a seal, with an outlet at its top and an inlet at its base. Used in plumbing fixtures that are too low to the floor for installation of a P-trap.

DWV - Drain, Waste, Vent

In the plumbing trade the acronym DWV stands for Drain, Waste and Vent. These are the three main parts that make up a plumbing drainage system which carries, and removes waste and rain water, other liquids, and human excreta from fixtures to a sewer or other disposal receptacle.

Eccentric reducer

An eccentric reducer is useful at the suction side of a pump system when the fluid the pump drives could contain another substance with different density, for example, water with air bubbles or oil with water. The purpose of the eccentric reducer is to properly mix substances that have different densities to reduce variations in the pump system.

Elbow Fitting

And elbow fitting or ell is a plumbing fitting installed between two lengths of pipe or tube allowing a change of direction. The name comes form the shape of the fitting, it is shaped like an elbow with two openings that changes the direction of the line allowing water to flow in a curve.

Emergency stop valves

An emergency stop valve, or straight stop valve, is valve that does not change direction. They are usually installed before the water supply line (below) to toilets and faucets. Angle stops are to be shut off in case of an emergency or repair and are generally not designed for daily on and off usage. The difference between a straight stop and an angle stops is the angle stop changes direction by 90 degrees while a straight stop is like most valves and does not change direction.

End Bell

An end bell or end bell fitting is attached to one pipe end to provide a socket or bell into which another pipe end can be fitted.


Plumbing equipment, not present in all systems, include, for example, water meters, pumps, expansion tanks, backflow preventers, filters, water softeners, water heaters, wrenches, heat exchangers, flaring pliers, gauges, and control systems.

Face Seal

A face seal is typically incorporate an O-ring that mate against the face of the opposite connector to form the seal. Depending on the standard, the O-ring may be on the nose of the male threaded connector, or behind the male thread on the face of the backing nut.


A ferrule is a sleeve-type fitting that slip over two ends to join them together. These fittings can be compressible and used as the sealing component of a compression fitting. They are also used as weldable connection fittings.