Standard Tubes:
Types of Copper Tube

Long lasting copper tube is a favorite choice for plumbing, heating, cooling and other systems. In the United States, it is manufactured to meet the requirements of specifications established by ASTM International.

All tube supplied to these ASTM standards is a minimum of 99.9 percent pure copper. The copper customarily used for tube supplied to these specifications is deoxidized with phosphorus and referred to as UNS C12200 or DHP1 Copper. Other coppers may also be used.

Table 14.1 identifies the six standard types of copper tube and their most common applications.2 The table also shows the ASTM Standard appropriate to the use of each type along with a listing of its commercially available lengths, sizes and tempers.

Types K, L, M, DWV and Medical Gas tube are designated by ASTM standard sizes, with the actual outside diameter always 1/8-inch larger than the standard size designation. Each type represents a series of sizes with different wall thicknesses. Type K tube has thicker walls than Type L tube, and Type L walls are thicker than Type M, for any given diameter. All inside diameters depend on tube size and wall thickness.

Copper tube for air-conditioning and refrigeration field service (ACR) is designated by actual outside diameter.

"Temper" describes the strength and hardness of the tube. In the piping trades, drawn temper tube is often referred to as "hard" tube and annealed as "soft" tube. Tube in the hard temper condition is usually joined by soldering or brazing, using capillary fittings or by welding.

Tube in the soft temper can be joined by the same techniques and is also commonly joined by the use of flare-type and compression fittings. It is also possible to expand the end of one tube so that it can be joined to another by soldering or brazing without a capillary fitting—a procedure that can be efficient and economical in many installations.

Tube in both the hard and soft tempers can also be joined by a variety of "mechanical" joints that can be assembled without the use of the heat source required for soldering and brazing.


1. Phosphorous-Deoxidized, High Residual Phosphorous Copper; 
2. There are many other copper and copper alloy tubes and pipes available for specialized applications. For more information on these products, contact CDA.