This part of ISO 4427 specifies the general aspects of fittings made from polyethylene (PE) for piping systems intended for the conveyance of water for human consumption, including raw water prior to treatment and water for general purposes. It also specifies the test parameters for the test methods to which it refers. In conjunction with the other parts of ISO 4427, it is applicable to PE fittings, their joints, to joints with components of PE and to joints with mechanical fittings of other materials, intended to be used under the following conditions: a) a maximum operating pressure (MOP) up to and including 25 bar1); b) an operating temperature of 20 °C as the reference temperature. NOTE 1 For applications operating at constant temperatures greater than 20 °C and up to 40 °C, see ISO 4427-1:2007, Annex A. NOTE 2 ISO 4427 covers a range of maximum operating pressures and gives requirements concerning colours and additives. 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 guidance or regulations and installation practices or codes. It is applicable to fittings of the following types: ⎯ fusion fittings — electrofusion fittings, butt fusion fittings and socket fusion fittings (see Annex A); ⎯ fabricated fittings (see Annex B); ⎯ mechanical fittings; ⎯ flanged fittings. 1) 1 bar = 0,1 MPa = 105 Pa; 1 MPa = 1 N/mm2.