1.1 This specification covers crosslinked polyethylene (PEX) pipe that is outside diameter controlled in metric pipe sizes (DN 16 to 1000) and inch pipe sizes (NPS 3 to 54), and pressure rated (see Appendix X1) using the MRS rating system. This specification is intended for PEX pipe made by various processes, as long as the PEX pipe made by that process meets all the requirements of this specification. Included are requirements and test methods for material, workmanship, UV protection, dimensions, hydrostatic sustained pressure, environmental stress cracking, stabilizer functionality, bent-pipe hydrostatic pressure, oxidative stability in potable chlorinated water, minimum operating temperature, degree of crosslinking, and hydrostatic burst pressure. Requirements for pipe markings are also given. The pipe covered by this specification is intended for pressure piping applications such as, industrial and general-purpose pipelines, potable water pipelines, fire – extinguishing pipelines, oil and gas producing applications to convey fluids such as oil, dry or wet gas, gas gathering, multiphase fluids, and non-potable oilfield water, and chemical pipelines. It is not intended for municipal natural gas distribution or for indoor flammable gas applications.

1.2 This specification also includes requirements for qualifying joints made using polyethylene electrofusion fittings and PEX pipe. Installation considerations are in X3.2.

1.3 The text of this specification references notes, footnotes, and appendixes, which provide explanatory material. These notes and footnotes (excluding those in tables and figures) should not be considered as requirements of the specification.

1.4 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.