This part of ISO 21003 specifies the general aspects of multilayer piping systems intended to be used for hot and cold water installations within buildings for the conveyance of water whether or not intended for human consumption (domestic systems) and for heating systems, under design pressures and temperatures according to the class of application (see Table 1).This standard covers a range of service conditions (application classes) and design pressure classes.The polymeric materials used for the stress bearing layers are the following: polyethylene of raised temperature resistance (PE-RT), polybutylene (PB), crosslinked polyethylene (PE-X), polypropylene