All PEX tubing carries one of three grades: PEX-A, PEX-B, or PEX-C. PEX stands for polyethylene (PE) cross-linked (X), and the grades are based on the various methods that manufacturers use to cross-link polyethylene molecules.
PEX-A represents the highest grade. Cross-linking occurs while the polyethylene is in a liquid form, resulting in even cross-links throughout the tubing. Known as the Engel or Peroxide Method, this production style yields PEX that has superior shape memory. PEX-A’s shape memory gives it several advantages, including added freeze resistance and flexibility. Kinks in PEX-A can be fixed through the application of heat from a heat gun, and only PEX-A tubing works with expansion-style fittings.
The Silane Method creates PEX-B tubing, with cross-linking occurring in solid-state polyethylene following pipe extrusion. The PEX-C Irradiation Method forms cross-links in PEX using beams of electrons after it has been shaped into tubing. This is the least common method of PEX manufacturing. PEX-B and PEX-C may be a bit stiffer than PEX-A, but are just as durable and reliable. See SupplyHouse.com for more information.