PEX is much less expensive than copper and galvanized steel pipe, and about the same price as PVC and CPVC pipe. However, "PEX pipe" is a general term that includes three pipe categories with different characteristics and price ranges.
PEX-A pipe, manufactured using the "thermal" crosslinking method. The method involves crosslinking polyethylene molecules at temperatures above the melting point of the polymers used. PEX-A pipe is more flexible than PEX-B and PEX-C pipe, expanding or contracting more when exposed to hot or cold water. This type of pipe also has the highest resistance to cracking when temperatures drop below freezing. Given its unique characteristics, it's easy to see why PEX-A is more expensive than PEX-B and PEX-C pipe.
PEX-B pipe is produced by placing the pipe in a hot water bath after using a catalyst in the extrusion process. PEX-B is stiffer than PEX-A due to molecular cross-linking between 65% and 70%. Therefore, PEX-B does not swell as well as PEX-A.
PEX-C pipe is fabricated with the help of electron radiation beams, which break existing bonds between molecules and create new crosslinks. With the least degree of cross-linking, this is the stiffest piping option, prone to kinks and cracks in freezing conditions.
