A coupling for non-metallic flexible electrical conduit is formed of a one piece lightweight molded thermoplastic cylindrical sleeve having a pair of threads extending inwardly toward opposite ends. Spaced axially inwardly from the inner end of each thread is an annular sealing ring having a sloped leading face and a perpendicular trailing face with the faces intersecting at a sharp annular edge. Lengths of conduit are engaged over opposite ends of the coupling and rotated to advance the conduit lengths over the sleeve. A liquid tight engagement is effective between each conduit length and the coupling when the conduit length advances past the sealing ring.