There are three grades of PEX tubing: PEX-A, PEX-B, and PEX-C. All PEX tubing is made of cross-linked polyethylene. The grades refer to the various methods that manufacturers use when linking the polyethylene molecules.
PEX-A carries the highest grade. Cross-linking takes place while the polyethylene is melted, resulting in even cross-links throughout the tubing. This “Engel Method” makes PEX easier to work with and allows it to retain its shape better than PEX of the other grades. Only PEX-A tubing works with expansion-style fittings.
The Silane Method creates PEX-B tubing. In this method, cross-linking occurs in silicon and oxygen molecules, rather than carbon. PEX-C (the Irradiation Method) creates cross-links in the PEX similar to those found in PEX-A tubing, but not while the polyethylene is in its liquid form. Instead, beams of electrons cross-link the polyethylene after it has been shaped into tubing. This is the least common method of PEX manufacturing. See SupplyHouse.com for more information.
