Compression fittings used with copper or plastic tubing seal by means of what?

Compression fittings used with copper or plastic tubing create a seal through the use of a compressed beveled gasket. When a compression fitting is tightened, the fitting compresses the gasket against the pipe, creating a watertight seal. This system is effective because it ensures that as pressure is applied, the gasket conforms to the surface of the tubing, preventing leaks.

In contrast, a threaded connection involves physically screwing together two parts, relying on the threads to maintain a seal. Solder joints require a melting process to join materials together, making them permanent and not easily adjustable. A welded connection also involves fusing materials together, which creates a very strong, but also permanent bond that isn't suitable for applications where flexibility and adjustments are needed. Thus, the use of a compressed beveled gasket in compression fittings offers both reliability and ease of disassembly when necessary.