ISO 4437-5:2014 specifies the requirements of fitness for purpose of the polyethylene (PE) piping system to be used for the supply of gaseous fuels.It specifies the definitions of electrofusion, socket fusion, butt fusion, and mechanical joints.It specifies the method of preparation of test piece joints and the tests to be carried out on these joints for assessing the fitness for purpose of the system under normal and extreme conditions.It specifies the test parameters for the test methods referred to in this part of ISO 4437.In conjunction with ISO 4437-1, ISO 4437-2, ISO 4437-3, and ISO 4437-4, it is applicable to PE pipes, fittings, valves, their joints, and joints with components of PE and other materials intended to be used under the following conditions: the maximum operating pressure (MOP) is based on the design stress, determined from the compound minimum required strength (MRS) divided by the C factor, and taking into account rapid crack propagation (RCP) requirements; and a temperature of 20 °C is taken as reference temperature for the design basis.