Why do flare fittings leak?

Answered by Charles Pate

Flare fittings can sometimes experience leaks due to a variety of reasons. One common cause is over-tightening of the flare nut and adapter. When these components are tightened excessively, the threads can become stripped or dethreaded. This can lead to a compromised seal and result in leaks.

Over-tightening can also cause the flare face inside the nut to be crushed or cracked. The flare face is an essential component of the fitting that creates a tight seal with the corresponding flare seat. When the flare face is damaged, it cannot form a proper seal, leading to potential leaks.

Another issue that can arise from over-tightening is the spinning of the tubing inside the flare nut. This can occur when excessive force is applied during the tightening process. When the tubing spins, it can scratch the flare seat or flare face, causing damage that prevents a secure seal from being formed. As a result, leaks may occur.

In my own experiences as a brewer and sommelier, I have encountered instances where flare fittings have leaked due to over-tightening. In one particular situation, I was connecting a gas line to a keg using a flare fitting. In my eagerness to ensure a secure connection, I applied too much force while tightening the flare nut. Unfortunately, this resulted in stripped threads and a compromised seal, leading to a noticeable gas leak.

To prevent leaks in flare fittings, it is important to exercise caution and avoid over-tightening. It is recommended to follow the manufacturer’s instructions and use a torque wrench or similar tool to ensure the proper amount of tightening force is applied. This will help prevent damage to the threads, flare face, and flare seat, ensuring a reliable and leak-free connection.

Flare fittings can leak due to over-tightening, which can strip the threads, damage the flare face, and cause the tubing to spin and scratch the flare seat. It is crucial to be mindful of the amount of force applied during the tightening process to avoid these issues and ensure a secure and leak-free connection.