Garbage Disposer Installation & Repair

Garbage disposer installation & repair can seem daunting to some of my customers. I routinely try to convince them that they can do it themselves. I’ll try to convince you with the following DIY plumbing tips with regards to garbage disposer installation & repair.

How to Install a new garbage disposer

  1. Disconnect the power – Turn off the power to the disposal by pulling the fuse or switching off the circuit breaker that controls the unit. Most disposals have power cords that run from the underside of the disposal to a switch-controlled outlet under the sink. To be sure the power is off, we prefer to run the disposal while a helper at the main service panel locates the right fuse or circuit. When the circuit is shut off, the disposal will stop. If the outlet under the sink is corroded or otherwise in bad repair, we suggest hiring an electrician to replace it. You can’t be too careful when electrical connections are near water.
  2. Remove the disposal – Use a pipe wrench, a large adjustable wrench or a large pair of tongue-and-groove pliers to undo the slip fittings on the P-trap, and release the trap’s contents into a bucket. (You may also find a cleanout plug on the underside of the pipe.) Once the P-trap is drained, remove hose clamps, discharge tubes and any other fittings that connect the old disposal to the drainpipe.Hold the disposal from underneath with one hand while you loosen the screws on the side of the mounting assembly. (The disposal probably came with a special tool for those screws, but chances are you won’t be able to find it. In that case, use a screwdriver.) Turn the assembly counterclockwise to release the disposal from its mounting.
  3. Disconnect the disposal’s electrical wiring – Once the disposal is disengaged, remove the screws securing its electrical cover plate, which is usually on the bottom of the unit. Then, to be doubly sure that the power is off, carefully remove the wire connectors that join the wires inside, and use a voltage tester to test individual wires. If there’s no current, pull the wires apart and loosen the clamp that holds the electrical cable. Pull the cable out of the unit.Blue Springs, MO & Grain Valley, MO garbage disposer installation
  4. Remove the old mounting ring and sink flange – Use a screwdriver to pry off the snap ring on the old mounting assembly, and remove the screws that connect the mounting ring to the sink flange. Pull the mounting ring away from the sink flange and remove any backup rings, gaskets or other parts of the mounting assembly.From above, pry the sink flange out of the drain hole. Clear any remaining plumber’s putty, old sealing gaskets or other debris from the area before you install the new hardware.
  5. Disassemble the new disposal hardware – Most new disposals are shipped assembled, so you have to disengage the mounting assembly from the body of the disposal, then pry the snap ring off of the mounting ring with a screwdriver. This should unlock the separate pieces of the mounting assembly. If you have trouble with this step, consult the manufacturer’s directions.
  6. Install the mounting assembly – Apply a 3/8 inch bead of clear silicone around the rim of the sink flange where the rim meets the sink drain hole. From above the sink, press the flange into the drain hole.From underneath the sink, install the gasket, the backup ring if one comes with your model, the mounting ring and the snap ring over the neck of the sink flange. Tighten the screws on the mounting assembly, alternating screws as you tighten, until the ring is uniformly secure. Then, from above, remove any excess silicone from around the flange seal.
  7. Make the electrical connections Remove the electrical cover plate on the new disposal. Insert the power cable at least 6 inches into the disposal’s cord connection slot and tighten the clamp screws. Pull the cord’s wires and the unit’s wires together inside the disposal’s electrical box. As needed, strip and splice the white wires to white and black to black using wire connectors. Connect the green ground wire to the grounding screw on the disposal, then replace the cover plate.
  8. Connect the discharge tube to the disposal – Use the hardware provided to attach the discharge tube to the discharge outlet on the side of the disposal.
  9. Mount the disposal – Hold the disposal up against the mounting assembly, and turn the mounting ring clockwise until the disposal locks into place. Tighten the screws on the mounting assembly with a screwdriver or the tool that comes with the disposal. Rotate the disposal so that the discharge tube can be easily connected to the drainpipe.
  10. Install the plumbing – Connect the disposal to the P-trap and the trap to the drainpipe. (The layout of your drain assembly may vary, depending on space constraints and whether you have a one- or two-bowl sink.) Tighten the parts by hand, then finish the job with a pair of tongue-and-groove pliers.


When all the plumbing is in place, run water through the disposal to test for leaks and tighten the connections on any loose joints. Plug the disposal’s power cord into the switch-controlled outlet that the old disposal was connected to, and turn the power back on. Use any available food scraps to make sure that the disposal works properly.

Tip From the Pros

– Don’t forget the knock out plug in the garbage disposer barbed drain connection if you’re dishwasher drains into it. Your dishwasher won’t drain if you forget to remove it.

– Feed a lemon through the disposal once a month to keep it smelling fresh.

– Hire your local master plumber at Advocate Master Plumbing to install a garbage disposal. Since it’s a straightforward job, you can probably get an installation estimate over the phone.

Recommended tools and supplies

  • Adjustable wrench
  • Garbage disposal
  • Caliper
  • Clear 100% silicone
  • Flashlight
  • Pipe wrenches
  • Screwdrivers
  • Tongue-and-groove pliers
  • Voltage tester

How to unjam a garbage disposer

If your disposer is humming but not running when you flick the switch, there’s something caught in the grinder chamber. Follow these steps:

  1. Unplug your garbage disposer.How to unjam your garbage disposal
  2. Using the hex allen wrench wiggle the motor back and forth. This should dislodge the offending material.
  3. With a flashlight inspect the grinder chamber.
  4. Use a pair of needle nose plyers to remove the material.
  5. Plug the garbage disposal back in and test with water. Be sure to inspect the bottom for leaks as jams can sometimes cause a catastrophic seal leak. If you see wagarbage disposer reset buttonter dripping from the base of the disposer, unplug it and call a plumber.