Abstract: A plastic pipe coupling system including a female coupling and a support ring. A circumferential groove is molded or cut into the outer diameter of a plastic pipe. The female coupling includes a reduced diameter portion with a coupling rib at the free end. The ends of the pipe, coupling, and support ring are beveled in order that the ends pressed together engage and by the slight resiliency of the plastic construction permit the slight expansion and contraction of the ends to provide a locking interfit of the respective groove and rib at the two ends. There is an interference fit between the support ring and the coupling so that a radial preload is induced when the support ring is assembled onto the coupling. The inner surface of the sleeve or the outer surface of the coupling is tapered for ease of installation of the support ring over the coupling and to provide radial support to keep the coupling in the groove.