Abstract: A coupling device for a liquid conduit system has a body defining a liquid flow passage and having an orifice defined by a generally cylindrical surface about an axis, and, disposed within the orifice, an insert. The cylindrical surface of the orifice defines a shoulder surface disposed generally parallel to the orifice axis. The insert has a threaded inner surface, and is sized for rotation relative to the orifice surface in a first direction about the orifice axis. The insert also defines an engagement surface that engages upon the orifice shoulder surface to restrict rotation of the insert relative to the orifice surface in the second, opposite direction. The insert is a split ring, and the engagement surface is defined by a radially aligned surface of the split ring.