Material storage container comprising a metal insert fitting

A bulk storage container (10) includes a tank (12) with a "full drain" outlet, and a coupler (14) attached to the outlet, in which the full drain outlet and coupler (14) utilize a metal-on-metal threaded connection to create a fluid-tight seal therebetween. The polymer coupler (14) includes a metal insert (28) with internal threads (52), and the tank (12) includes a metal insert (28) with external threads (32) corresponding to the internal threads (52) of the coupler insert (46). The metal inserts (28, 46) are integrally molded within the walls (16, 32) of the tank (12) and coupler (14), respectively. Advantageously, the threaded metal inserts (28, 46) provide a rigid structural connection between the tank (12) and coupler (14) that is highly durable and leak resistant. In addition to the threaded fluid-tight seal, a shoulder (56) of the coupler (14) abuts a corresponding face (58) formed on the tank (12), with a gasket (60) between the shoulder (56) and face (58) to provide a secondary seal.