There are three categories of methods to join copper tubing:
Solder or Brazed Joints
These joining methods include soldering, brazing and electric resistance. Soldered joints, with capillary fittings, are used in plumbing for water lines and for sanitary drainage. Brazed joints, with capillary fittings, are used where greater joint strength is required or where service temperatures are as high as 350°F.
Brazing is preferred, and often required, for joints in air-conditioning and refrigeration piping. Electric resistance joining is a flameless way to make soldered joints, although heat is still generated.
Copper tube may also be joined by butt-welding without the use of fittings. Care must be taken to use proper welding techniques. Welding methods are covered in CDA publication A1050, Welding Copper and Copper Alloys.
Flameless mechanical joining methods have been used for decades for underground tubing, for joints where the use of heat is impractical and for joints that may have to be disconnected from time to time. Traditional methods include flared joints and roll groove coupling systems.
Newer methods for most general plumbing applications include solderless press-connect and push-connect fittings, which incorporate an elastomeric gasket or seal (such as EPDM). The ranges of pressure-temperature ratings for no-flame joints are found in Table 4b.
Additional Joining Methods
Mechanically formed extruded outlets or tee-pulling is typically used in a variety of plumbing and piping applications where tee-connections are frequently encountered. Tee-pulling is a mechanical process; however, it requires a brazed joint for completion. Soldering of the branch tubing into the mechanically formed tee is not permitted.