How Do I Ensure that I Am Getting Quality Copper Tube & Fittings?

To ensure that copper tube and fittings are of the highest quality; meet market needs and requirements; and comply with governing codes, you should always verify that they meet applicable product standards. In the United States, copper tube and fitting standards have been developed through third-party consensus bodies, primarily ASTM International and the American Society of Mechanical Engineers (ASME).

The most common copper tube and fitting standards are listed below.

These standards establish a series of critical requirements, along with tests designed to verify compliance with such requirements. Compliance with these standards ensures not only that these products are of the highest quality, but also that they meet the requirements of the plumbing, mechanical and other codes that govern the use and installation of piping systems.

Some of the critical requirements established by these standards include:

1. Dimensional Requirements – Not only do these help to identify the standard size of the tube or fitting, but more importantly, they ensure that the copper tube and fittings fit together to create a strong, leak tight system.
   • Outside diameter (OD) and inside diameter (ID) – Particularly important in the tube standards, the outside diameter of the tube (along with appropriate tolerances ensure proper fit of the tube inside the fitting. These dimensions are critical to establish the optimum capillary space between the tube and fitting in soldered and brazed systems, and to ensure adequate tube to fitting interface in mechanical and press-fit joining systems.
   • Inside diameter (ID) – this is particularly important in the fittings standards for the same reason OD is important in the tube standards.
   • Wall thickness – copper tube is available in different types (wall thicknesses) to meet the pressure ratings of different systems. The wall thickness requirements ensure that the tube is able to withstand these pressure ratings with an adequate safety factor.
   • Insertion depth/Cup depth – For copper fittings, the insertion or cup depth is important to ensure that the resulting joint between the tube and fitting is adequate to meet the pressure ratings of the systems in which they are used.
2. Chemistry Requirements – Different tube or fitting products can be made using a number of standard copper alloy compositions. For example, most copper tube is made of UNS alloy C12200, meaning that the material is minimum 99.9% copper, with a maximum of 0.04% phosphorus. Each tube and fitting standard outlines the alloys suitable for that product to promote proper workability, strength, and chemical compatibility.
   
   
3. Mechanical Properties – Each standard may establish a set of mechanical properties (e.g., minimum yield or tensile strength, elongation, etc.) for the alloys and tempers to which the tube or fitting product is manufactured.
   • Tensile and yield strength properties ensure the strength and pressure rating of the product.
   • Elongation ensures that the product can be worked and formed, for example in tube bending, flaring, etc.
4. Grain Size – During manufacture, copper alloys crystallize into specific grain structures based on their alloy composition. To ensure proper workability and flexibility for use in normal operations, grain size is especially important to copper tube. A grain size that is too small can lead to more rapid “work hardening” of the tube, which can lead to bending/kinking issues and cracking during tube installation.
   
   
5. Hydrogen Embrittlement – These standards require that testing be conducted to ensure that the copper tube and fittings do not react with oxygen, thereby becoming brittle during high temperature operations like soldering and brazing.
   
   
6. Cleanliness – For copper tube and fittings that are used for specific applications, like medical gas (ASTM B819) and HVACR systems (ASTM B280), additional cleanliness requirements are included in the standards to ensure that the interior tube surface does not introduce any contaminants that might interfere with the safety or operation of the system. In medical gas systems, this prevents contamination of the gases used in healing and maintaining life. In HVACR systems, the cleanliness standards ensure that incompatible residues do not react with the refrigerant or cause clogging of compressors, orifices or other system equipment.

The examples listed above represent only a portion of copper tube and fittings standards and their requirements. For more information on the different types of copper tubes and fittings, their applicable standards, applications, dimensions, identification, pressure ratings, etc., please visit our Copper Tube Handbook or Guide Specifications on Plumbing.