How do I replace a garbage disposal?

Set up first, and you avoid a trip to the store with the sink torn apart.

• The new unit. Match horsepower and mounting to your sink and your household. Our page on what size garbage disposal you need covers the choice.
• The power. Waste King and Moen both say to unplug the old disposal, or turn off the power at the breaker or fuse box if it is hardwired. Both also say that if you are not familiar with electrical power and procedures, you should call a qualified electrician.
• The outlet and switch. Both makers require a dedicated switch with a marked "Off" position, installed within sight of the sink opening or the disposal. If your grounded 110 to 120 volt outlet is missing, both say to have a proper outlet installed by a qualified electrician.
• Tools and parts. Waste King's sheet recommends a set of helpful tools for a swap. Plan on a wrench for the drain line, pliers, a screwdriver, a hammer and plumber's putty or the rubber gasket that comes in the box.

Both instruction sheets give the same order. Work slowly, because a disposal is heavy and it will fall when it comes loose.

1. 1Cut the power. Unplug it. For a hardwired unit, turn off the breaker or fuse.
2. 2Disconnect the drain line. Use a wrench where the drain line attaches to the disposal discharge tube.
3. 3Disconnect the dishwasher hose, if there is one. Make sure the dishwasher is not running first.
4. 4Support the disposal and release the mounting ring. Both sheets say to support the unit while you disconnect the lower mounting ring, or it may fall. Turn the ring to release it. If it will not turn, both say to tap one of the ring's extensions with a hammer.
5. 5Disconnect any hardwired wiring after the unit is off the flange.

If you plan to reuse the sink flange, inspect the seals. If you cannot reuse it, remove the old flange and clean the sink thoroughly. Both makers also suggest a small extra. Waste King calls it a helpful hint: this is a good time to clean out the trap and drain lines with an auger or snake, unless your home is new.

The order of the mounting parts matters, so follow the sheet for your brand. Waste King says to pay close attention to the order of the mount assembly parts, which the factory assembled correctly.

1. 1Seat the sink flange. Set the flange in the center of the drain opening. Moen says to press the flange down firmly and not to move or rotate it once it is seated, or the seal may be broken. Waste King says the same: do not rotate the flange once seated, and use plumber's sealant or the rubber gasket, not both.
2. 2Test the seal before you go under the sink. Waste King says to put the stopper in and fill the sink with water to check the sink flange seal and make sure there are no leaks.
3. 3Attach the mounting parts. From underneath, Moen says to place the fiber gasket, backup flange and upper mounting ring on the flange in that order.
4. 4Hang the disposal. Move the discharge elbow into line with the drain connection, and hang the unit on the mounting ring. Moen says to align the three mounting tabs with the ramps and to tighten the lower ring until they lock. Waste King says to tap the ears with a hammer until the lock position is reached.

### What about the discharge elbow?

Use the new one. Waste King's sheet says "DO NOT RE-USE THE EXISTING DISCHARGE ELBOW AND GASKET AS THE GASKET MAY NOT SEAL PROPERLY." Moen's says the same. Both also say not to move the gasket onto the disposal. It has to stay on the elbow to seal.

### What about the dishwasher hookup?

Only do this if a dishwasher drains through the disposal. The dishwasher inlet is blocked by a knockout plug. Waste King and Moen both say not to use a screwdriver or sharp instrument, and to remove the plug with kitchen tongs after it drops into the unit, then throw it away. A plug left inside is a common cause of noise and jams, as our page on what to do when something falls into a disposal explains. If your dishwasher hose is a different size, use a dishwasher connector kit.

Finish the drain first, then the power.

• Reconnect the drain. Use a wrench to secure the drain line at the discharge tube.
• Clear the sink of tools, packaging and parts.
• Check every joint. Both sheets say all plumbing connections must be tight and in line with all plumbing codes and ordinances, and to contact a qualified plumber if in doubt.
• Run water and look for leaks. Watch the flange, the discharge elbow and the dishwasher inlet. Our page on why a garbage disposal leaks shows what each spot means.
• Then connect the power. Plug in the cord or complete the hardwire connection, turn on a medium flow of cold water, and run the disposal.
• Keep the stopper in. Waste King says to leave the stopper in the drain when the disposal is not in use, so utensils and other objects do not fall in.
• Run it properly. Waste King says to let the water and disposal run about 15 seconds after shredding stops.

If it does not start, the red reset button is the first check. Our page on where the reset button is shows where each brand puts it.

### Do you need a permit or an electrician?

Most of this is code-neutral, but two limits apply.

Permit. Many cities exempt like-for-like fixture swaps from a permit. The Phoenix building code, for example, lists replacing valves or fixtures with new ones that meet the code's water conservation rules, and repairing or replacing built-in appliances that are not regulated as building service equipment. The list is short, so check with your city if the job also moves pipe or the dishwasher connection. Our page on what plumbing work needs a permit in Phoenix explains the list.

Electrician. Call one for hardwiring, a missing outlet, no grounded outlet or a missing switch. Waste King's sheet says the plug must go in a properly installed, grounded outlet, and that improper connection of the grounding conductor can cause electric shock.

Hire one if the new unit does not line up with the old drain, if the flange is cracked or the sink needs new plumbing, if a dishwasher hookup is new, or if you are not comfortable working under the sink. HQ is licensed and insured, gives free estimates and upfront pricing, and can replace the unit and check the trap at the same visit.

Installing a new sink too? Our kitchen sink install guide covers the order of work.