ISO 15876-3:2003 specifies the characteristics of fittings for polybutylene (PB) piping systems intended to be used for hot and cold water installations, within buildings, for the conveyance of water which may or may not be intended for human consumption (domestic systems) or for heating systems, under design pressures and temperatures appropriate to the class of application. It covers a range of service conditions (application classes) and design pressure classes. It does not apply if the values of the design temperature, maximum design temperature and malfunction temperature are in excess of those given in ISO 15876-1. It also specifies the parameters for the test methods referred to in this standard. In conjunction with the other parts of ISO 15876, it is applicable to fittings made from PB and to fittings, made from other materials, intended to be fitted to pipes conforming to ISO 15876-2 to give joints conforming to the requirements of ISO 15876-5. It is also applicable to fittings made from alternative materials which, when fitted to pipes conforming to ISO 15876-2, give joints conforming to the requirements of ISO 15876-5. It is applicable to fittings of the following types: socket fusion fittingselectrofusion fittingsmechanical fittingsfittings with incorporated inserts.