scope:

INTRODUCTION

Many PEX plumbing systems are installed using some form of insert fitting, primarily produced from engineered polymers, as well as brass or other copper alloys. Because the insert portion of the fitting has a smaller diameter than the tube, the velocity of the water through the fitting is higher than the velocity of the water in the tube. Therefore, PEX systems delivering the same volume of water will have higher flow velocities in the tube and fittings than copper systems of the same nominal tube size.

Many plumbing codes have maximum recommended flow velocities for copper or copper alloys to prevent erosion of the material by the flowing water. Millions of brass insert fittings have been installed in PEX plumbing and heating systems over the past 40 or more years in Europe and North America. In that time, we are unaware of any erosion-induced failures of PEX piping systems.

To evaluate the subject of erosion corrosion of PEX copper alloy fittings, the Building & Construction Division of the Plastics Pipe Institute funded a test program at Materials Performance Inc. (MPI) in College Station, TX for performance testing of several designs of brass alloy PEX fittings. This testing was conducted in 1997 and 1998, but the findings are still considered relevant today.

Note 1: PE-RT tubing was not part of this study because it was not in use in North America during this time. It has since been approved in model plumbing and mechanical codes in the USA. PE-RT tubing is produced to the same dimensions as PEX tubing and product standards from ASTM International and CSA Group allow it to be approved for use with the same types of fitting systems and materials as PEX tubing. Brass fittings complying with the standards listed in this TN may also be used with PE-RT tubing.