In plumbing, what does the term "capillary" refer to?

The term "capillary" in plumbing specifically relates to the type of joint created during the soldering or brazing process, particularly when joining copper pipes. A capillary joint is formed when the molten solder is drawn into the small space between the pipe and the fitting due to capillary action—the phenomenon where liquid is attracted to surfaces and moves through narrow spaces.

This type of joint is crucial for creating a watertight seal in plumbing systems. Understanding capillary action is essential for plumbers as it influences the effectiveness of soldering techniques and ensures that connections are reliable and leak-free. A proper capillary joint can withstand temperature changes and pressure variations, contributing to the overall durability of the plumbing system. In contrast, the other options do not relate directly to this principle or practice in plumbing.