1.1 ,This specification covers crosslinked polyethylene (PEX) pipe that is outside diameter controlled in metric pipe sizes of DN 16 to DN 1000 (approximate outside diameters of 16 to 1005 mm) and inch pipe sizes NPS 3 to NPS 54 (approximate outside diameters of 3.5 to 54 in.), made in nominal pipe dimension ratios, and pressure rated for water at three temperatures (see Appendix X1). Included are requirements and test methods for material, workmanship, dimensions, burst pressure, hydrostatic sustained pressure, excessive temperature-pressure, environmental stress cracking, stabilizer functionality, bent-pipe hydrostatic pressure, oxidative stability in potable chlorinated water, degree of crosslinking, and minimum operating temperature. Requirements for pipe markings are also specified. The pipe covered by this specification is intended for pressure applications, such as, industrial and general-purpose pipelines, potable water pipelines, and fire–,extinguishing pipelines