This part of ISO 22391 specifies the characteristics of the fitness for purpose of piping systems made of ⎯ polyethylene of raised temperature resistance (PE-RT), Type I, and ⎯ polyethylene of raised temperature resistance (PE-RT), Type II, intended to be used for hot and cold water installations within buildings for the conveyance of water, whether or not the water is intended for human consumption (domestic systems) and for heating systems, under the design pressures and temperatures appropriate to the class of application according to ISO 22391-1.