Abstract: A connector assembly for attachment to the end of a compressible plastic covered conduit having a spiralling groove on the inside thereof, the connector assembly including an air impervious cylindrical sleeve member enveloping the compressible plastic covering and terminating at its outer end in a continuous annular inwardly and axially outwardly extending resilient seal-forming lip. A coupling member is provided having a sleeve portion with an external threading which snugly interfits with the spiralling groove on the inside of said conduit, thereby to expand the conduit outwardly to compress said compressible plastic conduit covering up against the inner surface of said sleeve member to form a liquid and airtight seal thereat. The coupling member has a flange which is axially held in a liquid and airtight sealing relationship with the continuous annular lip of the sleeve member.