Installing Garbage Disposals

A garbage disposal is a useful upgrade to your kitchen that is not too difficult to install. The hardest part is working under your sink, so work on plenty of towels to make it as comfortable as possible. If you’re installing a new sink, attach the disposal to the sink first, then set the sink in place. Begin by removing the trap from one of the sink strainers.

1. Supply electricity. If there isn’t one already, install an electrical box under the sink near the disposal. Install a GFCI receptacle and plug the disposal in. Or hard-wire the disposal. Unless you are using a self-switching disposal, install a switch as well.

2. Remove the basket strainer. Disconnect the trap assembly from the basket strainer and the drainpipe. Remove the locknut holding the strainer in place using the spud wrench or a hammer and screwdriver as shown. Lift out the strainer, and clean away old putty from around the sink opening using a putty knife, paint thinner, and an abrasive pad.

3. Install the mounting assembly. You’ll usually need to take apart the mounting assembly. To do this, remove the snap ring, mounting rings, and gasket from the flange. Lay a rope of putty around the sink opening and seat the flange in the opening. Have a helper hold the flange in place as you work from underneath. Slip the gasket, mounting rings, and snap ring up onto the flange. The snap ring will keep the mounting assembly in place temporarily. Tighten the mounting assembly against the sink by turning the screws counterclockwise, as shown. Tighten each screw a little at a time to assure a tight seal. With a putty knife, shave away excess putty.

Self-Switching Disposal - Most disposals will require a switched receptacle, leaving the homeowner with the difficult job of finding a good location for the switch. A wall switch usually means fishing an electrical line up the wall above the countertop. Another option is a switch on the face of the lower cabinets, but that puts it within the reach of children. To avoid these problems, spend the extra money for a self-switching garbage disposal. Just plug it into a regular always hot receptacle. It turns on when food is pushed into it.

4. Connect the electrical cord. Remove the electrical cover plate on the disposal. Strip sheathing and wire insulation from an approved appliance cord  and insert it into the opening. Tighten the clamp while holding the cord in place. Make the electrical connections in the disposal, ease the wires into place, and reinstall the cover plate.

5. Attach the disposal. Secure the drain elbow to the disposal. If you’ll drain a dishwasher through the unit, remove the knockout inside the nipple. To mount the disposal, lift it into place, and rotate it until it engages and tightens. (This may take some muscle.) Once the connection is made, rotate the disposal to the best position for attaching the drain lines.

6. Make the electrical connection. If you installed an electrical receptacle, simply insert the disposal’s plug. For a hard-wired installation, first shut off power. Then connect the source black wire to the switch black wire, the white switch wire to the black wire leading to the disposal, the white disposal wire to the white power source wire, and all the ground wires together.

7. Connect the drain. Fit a slip nut and a rubber washer onto the drain elbow, and fasten the trap to the elbow and the drainpipe. You may need to cut the elbow to make the connection. For double sinks connect the elbow to the second bowl drain. If you will be draining a dishwasher through the disposal, connect the dishwasher drain hose to the drain nipple of the disposal. Use an automotive clamp to attach the hose, tightening it in place with a screwdriver or ratchet and socket. Test for leaks by running water down through the disposal. Turn the electrical power back on. With standing water in the bowl, turn the disposal on, and make sure it is securely attached.

Tips on Installing the Drainpipes

  • On a double-bowl sink, it is possible to remove the drain elbow of the disposal and run pipe straight across to the trap of the other bowl. But the best way is to install a separate trap for the disposal so each bowl has its own trap.
  • If the original drain traps are in good condition, reuse them. In most cases if you buy one extension piece you will have enough material to complete the piping. If your old trap looks at all worn, save yourself a repair job later by replacing it while you have everything apart.

Maintaining Garbage Disposals

To avoid maintenance problems, be sure you have cold water running before you turn on your disposal. Gradually feed in food waste. Do not stick a spatula or any silverware down past the splash guard. With the cold water continuing to flow, run the disposal for a few seconds after the food has been ground. If you hear a clanking sound, or if the disposal stops, remove the object that has caused the problem by following the steps.

Remove stuck objects. If a fork, bottle cap, or any other solid object drops down through the splash guard, it can cause the disposal to jam. If this happens, turn off the power (if it has not already shut itself off). Remove the splash guard and peer down the disposal with a flashlight. If you can’t free the object, rotate the grinder with a broom handle.

Use a special turning tool. Your disposal may come with an Allen wrench that fits into a hole at the bottom of the disposal. If not, you can purchase a tool like the one shown. In either case, use the tool to turn the disposal back and forth. Once it’s free, remove any obstructions, replace the splash guard, turn on the cold water, and test the disposal.

Reset an overloaded disposal. If your disposal motor shuts off during operation, its overload protector has sensed overheating and has broken the electrical connection. Wait a few minutes for the unit to cool, then push the red reset button on the bottom of the disposal. If that doesn’t work, check to see that you have power to the unit by inspecting the cord and the fuse or circuit breaker.

Disassemble and auger the drain. Because a disposal gobbles up huge amounts of food waste, it’s to be expected that occasionally the drain line will clog. If this happens, disassemble and remove the P-trap (make sure you have a bucket handy to catch the water that will spill), and clean out the trap. If the trap itself is clear, thread a drain auger into the drainpipe.

Caution! - Don't Use Chemicals - Do not attempt to clear a blocked drain line with chemicals of any type—not even "safe" chemicals. If the solution does not work, you'll be in danger of getting spattered with the stuff when you work to clear the line.

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