Sink Only Drains When Garbage Disposal Is On

Since the invention of the garbage disposal in 1927 folks have been dealing with clogs.

Is your garbage disposal sink not draining? Many households have a kitchen sink that only drains when the garbage disposal is on. This kind of thing can hamper your plans, or bring all kitchen operations to a standstill.

There are two things you can do, call in the cavalry, or begin your own rescue mission.

The good news is that with a few household items and some detective work, you can find the source of the clog and fix it yourself. There are also some precautions you can take to prevent drainage issues in the future.

How a Garbage Disposal Works

Although disposals can vary, they all have the same basic design structure. The disposal is mounted underneath the sink. When the disposal is on, the impeller plate, or spinning disc, rotates rapidly.

This shreds the food into tiny pieces, which are small enough to be washed away with water through the holes in the shredding chamber. If the sink won’t drain unless the garbage disposal is on, your disposal is either jammed or clogged.

Troubleshooting: Steps to Diagnose the Problem


Clogs and improper drainage are the most common causes. If your sink isn’t working properly, you don’t have to give up right away and call a professional.

The first step in fixing a clogged sink that won’t drain unless garbage disposal is on is troubleshooting. Most jams are caused by seeds and other hard materials. Take the following steps if the garbage disposal sink is not draining. Complete each step, and proceed to the next if it still isn’t working.

  1. First, check for things in the drain trap. You’d be surprised what people put down there. I’ve seen keys, wallets, wedding rings, chopsticks, you name it.
  2. Check to see if the disposal drain is lower than the drain that is coming out of the wall. If so it needs to be raised up.
  3. Run the faucet, and turn the disposal on and off several times. The blades spin and create a vortex, forcing water past the unit and into the drain pipe. This can clear a small, simple clog.
  4. Try using an allen wrench to rotate the flywheel turning wrench hole. This is located on the bottom of the unit. Turn the wrench in either direction to see if it moves freely. This is basically a way of manually operating the disposal.
  5. If your model doesn’t have a wrench hole in the bottom, you can accomplish the same result by using the end of a broomstick or a wooden spoon. Insert the broomstick into the drain and hold it firmly against the impellers. Rotate counterclockwise.
  6. If you see a whirlpool in the water after you turn the disposal on, that means you have a clogged drain. Check to see if the drain line from the disposal is clear and free-flowing. Is the sink on the opposite side draining? If not you need to drain the line with a snake. If the drains aren’t clogged, you may have a mechanical issue with the disposal.
  7. A dishwasher outlet hose needs to connect an inlet pipe on the unit in order to comply with housing codes. This is also known as an inlet pipe or vent. If the dishwasher isn’t draining, you may need to replace the vent. This is an inexpensive part.

If the sink won’t drain unless the garbage disposal is on after you have followed the troubleshooting steps, you may need to call a plumber.

Do’s and Don’ts

Do’s and Don’ts

Garbage disposals can be a mystery. I remember how much I loved to watch food disappear down the drain when I was a kid. I was also terrified of the thing after I dropped a fork down the sink drain. If you have young ones in the house, make sure they don’t take the term “garbage disposal” literally. Or else you may be calling a plumber more often than you want. 

The most common causes of drainage issues are usually due to user error. To keep the appliance running smoothly and safely, be sure to follow these Do’s and Don’ts.


  • Only use cold water when you run the disposal. Let the water continue to run for 15 seconds after it grinds. 
  • Slowly feed items down the kitchen sink drain.
  • To prevent buildup, run the disposal regularly to remove any scraps of food that may be sitting in the chamber.
  • Grind ice in the disposal to clean the inside.
  • When not in use, cover the drain with a lid to prevent items from falling into the disposal.
  • Use citrus rinds to freshen the disposal. Baking soda also works well for removing odors. 
  • If it jams, immediately shut it off to avoid blowing the motor.


  • Run the disposal without water.
  • Let waste sit inside of the disposal.
  • Pour grease down the drain.
  • Grind fibrous materials from foods like asparagus, carrots, or artichokes.
  • Put pasta, rice, potatoes or other starchy foods down the drain.
  • Grind anything sharp or hard like large bones, seeds, or coffee grounds.
  • Reach in with your hands to remove a jam.
  • Pour heavy drain cleaners or chemicals into the disposal. 

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