This International Standard specifies a method to determine, for mechanically jointed polyolefin pipe and fitting assemblies in sizes of dn u 63 mm, the effect of component relaxation and creep on the resistance of the assembly to pipe pull out under the long-term application of a constant and longitudinally applied force. The susceptibility of the polyolefin pipe to stress crack failure initiated by the joint assembly is also examined. NOTE For sizes dn > 63 mm, the method is under development.