How to Install a New Garbage Disposal
1. Read the directions thoroughly! Models vary, so make sure you understand the installation procedure for your particular disposer.
2. Unplug the old garbage disposal and shut off the power to the outlet that the new disposal will be plugged into.
3. Disconnect the plumbing. You'll probably have one pipe leading from the water, and a second going to the dishwasher. Disconnect both. At the top of the disposal, a series of rings attach it onto the sink. One of these rings will have 3 large ring-type configurations coming off of it. Grab one of those configurations and twist the entire ring clockwise. It may be hard to get it to turn enough so the whole disposal comes right off into your hands; use tools if necessary.
4. Once the old disposal is off, take the opportunity to clean out your pipes to prevent future clogging.
5. If you are attaching your new disposal to your dishwasher line (the plumbing that comes out of the dishwasher to drain the water), you need to unplug the little hole in the new disposal first. To do this, take a screwdriver and a hammer and chisel it out.
6. Attach the electrical wiring to the new disposal. There are 2 different ways to connect power to your disposal - simply plug it into an ordinary outlet that is powered by the on/off switch by your sink, or connect it directly to the switch connection. If you have an outlet under the sink, here's what you do.
First, if you didn't buy a kit at the hardware store, take the electrical cord off the old disposal! When you look under the old disposal, you'll see the cord going into what appears to be a rather large nut, and next to that a metal plate. Unscrew the metal plate to reveal the electrical cord, spliced and connected to the disposal's engine cords. One cord is white and one is black. A third (green) one is attached to a screw in plain sight. Disconnect the green wire; mark which cord was spliced to the white and which was spliced to the black; then cut those connections with a wire cutter. That big nut thing actually comes off with the wire, so if you look inside, you will notice it is anchored on two sides by metal tabs. Gently bend the metal tabs back so you can ease the nut and cord out and off the old disposal.
7. Now, you need to connect the cord to the new disposal. First, unscrew the metal plate and place the end of the cord through the hole that the nut will be attached to (next to the metal plate). Gently bend the metal tabs back into place on the new disposal. Now simply splice the wires together, making sure you are connecting the white to the correct wire and the black to the correct wire. Expose about 1/2 inch of the green wire and connect that to the appropriate screw. Now screw the metal plate back on.
8. Now you are ready to install your new disposal. Hopefully, you were able to salvage the mounting rings from the old disposal. If not, follow the diagram in the instructions and attach the new mounting rings to the sink, using plumber's putty around the edges to prevent leaking. Next place the actual ring that will fit onto the mounting rings on the new disposal, and fit the rubber stopper on the top of the disposal. Now it's time to get under the sink. You want to mount the disposal onto the sink using the rings. Be sure all three parts of the mounting ring are connected, and turn all the way counter-clockwise until you hear a click. You may need locking pliers or even a hammer to coax the ring into locking position. Reconnect all of the plumbing, making sure to turn all of the threaded rings tight to avoid leaking.
9. Plug in your new disposal, turn the power back on, and run cold water in the sink. Check for leaks, and use a sealant if you need to or retighten the threaded rings. Now, with the water running, turn the new disposal on. You may want to run your dishwasher to check that you got the dishwasher hole open enough.
10. If learning how to install a garbage disposal isn't your thing, there's no shame in that. Hire a local professional to do it for you.
Updated November 18, 2018.
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