This part of ISO 21003 specifies the characteristics of fittings for multilayer piping systems intended to be used for hot and cold water installations inside buildings for the conveyance of water — whether or not the water is intended for human consumption (domestic systems) or for heating systems — under specified design pressures and temperatures appropriate to the class of application (see Table 1 of ISO 21003-1:2008). It also specifies the test parameters for the test methods referred to in this part of ISO 21003. ISO 21003 is a reference product standard. It is applicable to multilayer pipes, fittings, their joints, and also to joints with components made of other plastics and non-plastics materials intended to be used for hot and cold water installations. This part of ISO 21003 is intended for use only in conjunction with all the other parts of ISO 21003. This part of ISO 21003 covers fusion, solvent-cemented and mechanical fittings for a range of service conditions (application classes) and design pressures. It is not applicable for values of design temperature, TD, maximum design temperature, Tmax, and malfunction temperature, Tmal, in excess of those in Table 1 of ISO 21003-1:2008. NOTE 1 It is the responsibility of the purchaser or specifier to make the appropriate selections from these aspects, taking into account their particular requirements and any relevant national regulations and installation practices or codes. The polymeric materials used for the stress-designed layers are the following: polybutylene (PB), polyethylene of raised temperature resistance (PE-RT), crosslinked polyethylene (PE-X), polypropylene (PP) and chlorinated poly(vinyl chloride) (PVC-C). The PE-X used shall be fully crosslinked and shall comply with the requirements of the relevant reference product standard (ISO 15875). NOTE 2 For the purposes of ISO 21003, crosslinked polyethylene (PE-X) as well as adhesives are considered as thermoplastic materials.