How to Connect a Garbage Disposal Unit With a Dishwasher

Clean out the bottom sink cabinet and place a bucket under the existing J-trap pipe. Use a pipe wrench to loosen the pipe and remove the pipe. Dump any water collected in the trap pipe into the bucket.

Remove the large nut that holds the main drain pipe under the sink into place. Carefully unscrew the drain pipe from the sink base. This will cause the strainer assembly in the sink to rise up slightly. Use a small putty knife to trim away the old plumber's putty that helped seal the drain inside the sink, and lift the drain pipe out of the sink.

Connect the garbage disposal to the sink. Place a ring of plumber's putty around the sink opening at a bead size of approximately 1/4 inch, and then slip the sink-mounting assembly and flange piece through the hole and down into the cabinet beneath. Press the drain piece down into the putty to compress the bead and form a tight seal.

Attach the mounting ring, gasket and nut, and tighten them from the underside of the sink and onto the flange. Have an assistant press down slightly from above to make sure the drain doesn't spin in the putty. Hand-tighten the ring so it will not shift from the sink, and wipe away any putty that presses out into the sink from the tightening.

Prepare the disposal unit for the dishwasher by removing the plug from the dishwasher inlet tube mounted at the top of the mechanism. Using a flat-head screwdriver and a hammer, strike it once or twice to pop the plastic retaining piece into the unit. Turn the disposal upside down and it will fall out.

Line up the disposal with the mounting ring and lift it into place so it connects. It may take a few tries to get it attached, but you will feel it become much lighter when it hooks up. Turn the disposal slightly and it will tighten and finally lock into place with a click.

Connect the unit to the wall drain pipe, using the replacement J-trap that came with the disposal. Slide the pipe nut onto the pipe before lining up the washer to allow it to tighten over the washer. Tighten the nuts with a pipe wrench and verify that everything is tight and in position.

Connect the drain pipe from the dishwasher to the intake pipe at the top of the disposal and use a metal clamp to tighten it to the pipe. Check the connection to make sure it will not pull free.

Plug the disposal plug into the outlet under the sink and press the red reset button on the underside of the disposal to set the system for use. Turn the water on at the sink and verify that all connections are tight and there are no leaks.

Operate the electrical switch above the sink to activate the disposal and make sure it turns on. Be sure the water is still running when you do this or it may damage the unit. Begin filling the dishwasher, and then stop it and set it to drain to check the connection to the appliance.