Do all unions require a gasket to ensure a tight seal?

Not all unions require a gasket to ensure a tight seal, which makes this answer accurate. The necessity of a gasket depends on the design of the union and the materials being joined. Unions that have a precise machined surface may achieve a watertight seal simply through the compression of the metal surfaces against each other when tightened, effectively eliminating the need for a gasket.

In some cases, unions may utilize a form of a threaded connection or even a weld, which inherently provides a tight seal without additional sealing materials. Additionally, certain applications, particularly those involving high pressure or specific fluids, might mandate the use of gaskets to prevent leaks and ensure operational safety.

Understanding these variations is essential for a pipefitter, as it influences decision-making regarding materials and installation methods in various plumbing and HVAC systems.