If the PEX plumbing system, despite assurances of the seller, you do not have flowed through the 50 years, and 5, the cause is usually not the pipe, and errors in their installation due to incompetence in the choice of technology and pipe assembly.
First, the domestic market is filled with a variety of tubes, as high quality and of dubious provenance. All of them are advertised as products with half a century of operation. Note that the 50-year-old maintenance of PEX tubing in USA is considered the norm. To our unsophisticated consumers sufficient incentive for the purchase is just what his new pipes are made of PEX. Material and Quality of pipes take into account not many.
Secondly, even the pipes of high quality, but improper for the brand and size, pose a real threat of premature system failure. It is an error in the selection of pipes are, to date, the most common cause of trouble.
Third, mount technology requires a clear implication manufacturer’s instructions, which are not always respected. For example, some home “craftsmen”, bought in a store plumbing systems and delivering purchases home immediately assembling them. Meanwhile, during transportation and during their stay in warehouses and factory shop, on the sealing PEX pipe collects dust. This dust must be necessarily flushed, and the ring lubricated technical lubricant. Otherwise, the tightness of the system is broken.