This part of ISO 22391 specifies the general aspects of piping systems made of polyethylene of raised temperature resistance (PE-RT), 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) or heating systems — under specified design pressures and temperatures according to the class of application. It covers a range of service conditions (classes of application), design pressures and pipe dimension classes, and also specifies test parameters and defines terms, symbols and abbreviated terms. When used in conjunction with the other parts of ISO 22391, it is respectively applicable to PE-RT pipes, fittings, their joints, and to joints having components of PE-RT as well as of other plastics and non-plastics materials, used for hot and cold water installations. It is not applicable for values of design temperature, maximum design temperature or malfunction temperature in excess of those it specifies