There are two main parts to this project: First, getting power to the disposal with a switch so that the homeowner has a way to control it, and then reconfiguring the trap to hook it up.

It’s best if the disposal can be on it’s own dedicated circuit. This was not practical for this project, so the next best thing is to add it to the dishwasher circuit. This circuit should be 20 amps with 12/2 wire with only the dishwasher and disposal on it.

This worked well for this project because I would have to pull the dishwasher out anyway to have access to the wall and run the wires to a switch above the countertop. I used a junction box below in the basement to make all the connections and ran new wiring from there.

To put in the switch, I enlarged the opening next to a single switch box and replaced it with a new ‘remodeling’ double switch box. The ‘remodeling’ boxes have little flaps that go out when you screw them down and secure the box to the drywall. Fishing the wires through the wall went well once the dishwasher was out of the way and I could make a couple small holes in the wall behind it.

Under the sink I ran the disposal’s wire into a small plastic junction box with a cover. From here I was able to hardwire the disposal into the junction box.

NOTE: Many garbage disposals come with a ‘power cord’ connector with a plug on the end. In this case, I would install a 20 amp plug in the junction box and just plug the disposal into it.

Now for the plumbing part… I started by removing all the trap fittings under the sink because they needed to be replaced anyway. The tube that comes out of the disposal joins up with the pipe from the other sink and then goes down into the P-trap and out. It’s always a puzzle to find the right combination of pieces, but it helped to get the disposal in place first and then see how it would lay out.

It took an afternoon, but now this homeowner has a monster under the sink waiting for leftovers.

-Peter

www.CarpentryGuy.com