Plumbing Terminology - C

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Cap Fitting

In the plumbing trade with a cap fitting or cap is meant a type of pipe fitting, often liquid or gas tight, which covers the end of a pipe. A cap has a similar function to a plug. cap fittings are designed to attach over the outside of a tube end to dead-end the flow. A plug is inserted into the end of hose or tubing to dead-end the flow. Attachment techniques include welding, push-fit, brazing, adhesives, and threading.In plumbing systems that use threads the cap has female threads.

Catch Basin

A catch basin is a device that receives storm water drainage from an outside surface area. They are usually located in parking lots or in areas where the removal of storm water buildup is desirable. The catch basin is a part of a sewer system or storm drain that is designed to trap debris, preventing it from entering the drainage pipes.


A centerset is a type of faucet that has combined spout and handles, with the handles 4 inches apart - center-to-center. A single-handle faucet installed on 4 inches center-to-center faucet holes is also called a centerset.

Clean Out

Clean Out is a term used in the plumbing business to refer to the access to the sanitary or waste lines in order to be able to clean them out if they were clogged.

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