What technique is used for joining copper pipes in plumbing?

Soldering is the technique used for joining copper pipes in plumbing due to its effectiveness in creating a strong, heat-resistant joint. This method involves heating the copper pipes and applying a filler metal (solder), typically composed of a combination of lead and tin or lead-free alloys, to bond the surfaces together as it melts and flows into the joint.

The process requires precise temperature control to ensure that the solder adheres properly without damaging the pipes. Once cooled, the joint forms a durable connection that can withstand water pressure and thermal expansion, which is essential in plumbing systems.

Other techniques mentioned, such as welding, typically operate at much higher temperatures and are not commonly used for copper pipe connections due to the risk of damaging the pipe material. Gluing is not suitable for metal pipes, and threading involves mechanical joining methods that do not create a seamless, leak-proof connection like soldering does. Therefore, soldering remains the preferred method for securely joining copper pipes in plumbing systems.