This specification covers requirements, test methods, and methods of marking for crosslinked polyethylene plastic hot- and cold-water distribution systems components made in one standard dimension ratio. Components are comprised of tubing and fittings intended for use in residential and commercial, hot and cold, potable water distribution systems as well as sealed central heating, including under-floor heating systems. Requirements and test methods are included for materials, workmanship, dimensions and tolerances, burst pressure, sustained pressure, excessive temperature and pressure, temperature cycling tests, and bend strength. Also included are tests related to system malfunctions.