CPVC and PEX are both ductile. CPVC is rigid while PEX is flexible.  A key difference between PEX and CPVC is that PEX is highly crystalline and therefore is inherently resistant to hydrocarbon chemicals. CPVC, on the other hand, is incompatible with most hydrocarbon chemicals. Since hydrocarbon chemicals are everywhere, the most common cause of failure of CPVC is exposure to incompatible hydrocarbon chemicals while PEX is compatible with virtually all hydrocarbon chemicals. It is the combination the inherent chemical resistance of PEX with its extremely high ductility and flexibility that makes PEX a more reliable plumbing product than CPVC.