respectively heretofore leaks in underground plastic gas pipes had posed a serious problem since plastic pipes cannot be easily threaded and connected together in a leak free manner by threaded couplings fittings incorporating spigots formed with circumferential rings having rounded square or trapozoidal cross sections had proven totally inadequate to serve as a coupling to join the ends of damaged plastic pipe however with a repair coupling embodying the present invention it is possible to shut off the flow of for instance natural gas upstream of the leak excavate in the area of the leak to expose the leaking pipe for a plastic pipe having a 11 8 inch o d for instance the section in which the leak has occurred may then be simply removed by severing the pipe on both axial sides thereof to leave the exposed ends 82 and 83 disposed in confronting relationship spaced for instance three inches apart to bridge the axial space left between the ends of such pipe sections 81 and 85 the repair coupling generally designated 91 is formed with a pair of spaced apart flanges 90 and 92 which define therebetween a deep groove 94 projecting in one axial direction from the flange 90 is an elongated tube section 93 which mounts a spigot section 95 on the remote end thereof the spigot section 95 is formed on its periphery with axially spaced apart frusto conical sealing rings 97 which terminate at the enlarged ends thereof in radial locking faces 99 the opposite end of the fitting 91 is formed with a similar spigot section generally designated 101 which includes the frusto conical sealing rings 103 terminating at the enlarged ends thereof in radial locking faces 105 in operation a damaged polyethelene pipe may.