Drill a 3/4-inch hole in the side of the stock tank with a drill and hole saw, positioned about 1 to 2 inches above the bottom.
Turn a hose bib faucet with a 3/4-inch male connection clockwise into the hole to thread the hole for easier installation. Remove the faucet from the hole by turning it counterclockwise.
Wrap the threads of the male end of the faucet and the threads of the female coupler with a single layer of teflon tape. Apply silicone sealer to the faucet threads and to the areas where the faucet meets the outside of the tank.
Thread the faucet into the hole of the tank until the faucet rests tightly against the outside of the tank. Thread the female couple securely onto the male connector inside the tank.
Wipe off any excess silicone sealant. Let it dry completely.
Fill the tank with water to above the drain to test for leaks, making sure the faucet is in the closed or off position. Turn the faucet to the open or on position when you are ready to drain the tank.