Can you use brass compression fitting on PEX?

Brass compression fittings are not recommended for use with PEX (cross-linked polyethylene) pipes. This is because PEX pipes have a different thermal expansion rate than copper or brass, which can cause leaks to occur over time when brass compression fittings are used.

Compression fittings rely on the compression ring and nut to create a tight seal around the pipe. However, the compression ring may not be able to grip the PEX pipe as tightly as it would grip copper or brass due to the greater flexibility of PEX. This can lead to leaks developing between the fitting and the pipe over time.

Instead of brass compression fittings, it is recommended to use fittings specifically designed for use with PEX pipes, such as push-to-connect, barb, or crimp fittings. These fittings are designed to work with the flexibility of PEX and provide a secure, leak-proof connection that will last over time.