Abstract: A conduit system including conduit units which are interconnected by coupling units during field installation. The conduit units include a pipe, a pipe insulating body, a conduit jacket around the insulating body and conduit sealing members at opposite ends of the conduit unit. The coupling units include a coupling body for telescopically receiving ends of adjacent conduit pipes, an insulating body, a coupling jacket around the insulating body, and coupling sealing members at opposite ends of the coupling unit.When the coupling and conduit units are assembled the sealing member of one unit bridges the juncture of adjacent jacket ends to provide a primary seal against infiltration of moisture. The sealing members of adjacent units sealingly abut each other to provide a secondary seal against moisture infiltration spaced axially from the adjacent ends of the conduit and coupling jackets.