Final answer:
The technique for joining copper water pipes is called soldering, which uses molten solder to create a waterproof bond and is used in plumbing to ensure a safe water supply.
Step-by-step explanation:
The technique for joining copper water pipes is known as soldering. Soldering involves melting a metal called solder around the joint where two pipes meet. It creates a strong, waterproof bond that is suitable for plumbing. Unlike soldering, welding fuses the base metals together, and threading refers to creating a spiral ridge on the end of the pipe, which can be screwed into a fitting. Cementing is a method typically used for joining PVC pipes, not copper.
In the context of plumbing, especially when replacing hazardous lead pipes with copper ones, using a propane torch is a common method to solder copper plumbing pipes. This torch provides the necessary heat to melt the solder that seals the joint. The process is essential for ensuring safe and reliable water supply.