Defines a method for testing the leaktightness of assemblies of unplasticized poly (vinyl chloride) (PVC-U) pipes with elastomeric sealing-ring-type-socket joints including: double sockets; single sockets of pipes; and sockets of fittings. Also applicable to elastomeric-sealing-ring-type sockets made of ductile cast iron for use with PVC-U pressure piping.