Step 9 · Connect the Drain Plumbing
Now assemble the drain plumbing. Attach the tailpieces to the bottom of the sink strainer and the garbage disposal discharge. Connect the two tailpieces using a tee fitting. From the tee, install the P-trap, which connects to the drain line in the wall. Use slip nuts and washers at all connections. Hand-tighten all connections first, then give them a final quarter-turn with channel-lock pliers. Do not overtighten, as this can crack the plastic fittings.