Where should pipe joint compound be applied?

The correct application of pipe joint compound is typically to the male threads only, excluding the last two threads at the end. This practice is important because it helps to create a seal while preventing the compound from being squeezed into the pipe, which can contaminate the gas or fluid flowing through it. The last two threads are left free of the compound to ensure that no obstruction occurs at the entry of the pipe, maintaining a clear connection.

Applying the joint compound exclusively to the male threads allows for effective sealing without risking the integrity of the flow path. It also helps in achieving a tight seal that can accommodate slight deviations in the joint alignment or threading.

In contrast, putting compound on female threads or applying it to all threads may lead to excessive buildup, which could impede flow or create leaks. Similarly, coating the entire joint surface is unnecessary and can be detrimental to the connection's performance. The focus should remain on ensuring a secure yet unobstructed connection, reinforcing why it's standard practice to limit the compound application to the male threads, avoiding the last two threads.