The right size depends on your disposal model, but 1/8 inch is the most common

Most garbage disposals use a 1/8 inch hex key (also called an Allen wrench) to free a jammed flywheel. Some models use 3/16 inch or 5/32 inch instead. The size you need is printed in your disposal's manual, usually on the inside cover or a sticker near the motor. If you have lost the manual, the brand and model number are stamped on the unit itself — you can search that number online to find the spec sheet.

The hex key fits into a socket on the bottom of the disposal, directly under the flywheel. Turning it back and forth breaks up whatever is blocking the blades. You do not need to remove the disposal or take apart the sink — the key works from underneath, through the drain opening.

Key Takeaways

  • The 1/8 inch hex key fits most common disposal models, but your manual or model number will confirm the exact size.
  • The socket is on the bottom of the disposal unit, accessible from underneath the sink without removing the disposal itself.
  • Turning the key back and forth (not forcing it in one direction) dislodges the jam and lets the flywheel spin freely again.
  • If you cannot find your manual, the brand and model number on the disposal body will lead you to the correct size online.

Where to find the size on your disposal

Open the cabinet under your sink and look at the disposal unit itself. The brand name and model number are usually stamped or printed on a metal plate near the motor housing. Write down the full model number — it often includes letters and numbers together, like "InSinkErator 333" or "Waste King L-8000".

Search that model number plus "hex key size" or "Allen wrench size" in a search engine. The manufacturer's product page or manual PDF will list the socket size. If the manual is not online, call the brand's customer service line with the model number and they will tell you the size in under a minute.

If a sticker or label is still attached to the disposal, check there first — some manufacturers print the hex key size directly on it for quick reference.

Common sizes across major brands

InSinkErator disposals, which make up roughly half the market, typically use 1/8 inch. Waste King and Badger models also commonly use 1/8 inch. Moen and Kohler disposals sometimes use 3/16 inch or 5/32 inch instead. A few older or commercial models use 1/4 inch, though this is less common in residential kitchens.

Because the size varies, guessing is not worth the risk — forcing the wrong size into the socket can strip the hex fitting and make the disposal impossible to unjam later. Spending two minutes to confirm the size now saves you a service call later.

How to use the hex key safely

Before you touch anything, turn off the disposal and unplug it from the outlet under the sink. Do not rely on the wall switch alone — the plug must be out. Wait a few seconds for the motor to stop completely.

Reach under the sink and locate the hex socket on the bottom of the disposal. Insert the correct-size hex key into the socket. Turn it slowly back and forth — do not force it in one direction. You are trying to rotate the flywheel slightly to break up the jam, not to spin it freely yet. After a few turns in each direction, stop and try to turn the key by hand. If it moves more freely, the jam is breaking apart.

Once the key turns easily, remove it and plug the disposal back in. Run cold water and turn on the disposal briefly to clear the debris. If the jam does not clear after a few tries, the blockage may be too severe for the hex key alone — that is the point to call a plumber.

What to do if you do not have the right size

If you own a disposal but do not have a hex key at all, buy a set. A basic set of hex keys costs between $5 and $15 at any hardware store and includes sizes from 1/16 inch to 3/8 inch. You will have the right size for your disposal plus extras for other household tools.

If you have a hex key but it does not fit the socket, do not force it. Forcing the wrong size will damage the socket and make future unjamming impossible. Instead, measure the socket opening with a ruler or caliper if you have one, or take a photo and show it to a hardware store employee — they can match it to the correct size.

When the hex key alone is not enough

A hex key works for soft jams — food scraps, grease buildup, or small objects stuck between the blades. If the flywheel will not budge even after several attempts, or if you hear grinding sounds when you turn the key, the jam may be caused by something harder: a bone, a piece of plastic, or a utensil wedged deep in the chamber.

At that point, the disposal may need to be taken apart or replaced. This is a job for a plumber, not a DIY fix. Continuing to force the hex key risks damaging the motor or the socket permanently.

Frequently Asked Questions

Can I use a different size hex key if I do not have the right one?

No. Using the wrong size can strip the socket and make the disposal impossible to unjam later. Spend the time to find the correct size first. If you cannot find your manual, call the brand's customer service with your model number — they will tell you in minutes.

What if the hex key fits but will not turn at all?

The jam may be too severe for the hex key to break up. Do not force it — forcing can damage the socket or the motor. If the key will not budge after a gentle attempt, stop and call a plumber. Continuing to push risks making the problem worse.

Do I need to remove the disposal to use the hex key?

No. The hex socket is on the bottom of the unit, accessible from underneath the sink without removing anything. You reach up from below and insert the key into the socket. The entire process takes place under the sink with the disposal still mounted.

Where exactly is the hex socket located?

It is on the very bottom of the disposal unit, centered under the flywheel chamber. Look directly underneath the disposal and you will see a small hexagonal opening. That is where the key goes. If you cannot find it, check your manual — some older models place it in a slightly different spot.

Can I buy a hex key at any hardware store?

Yes. Any hardware store sells hex key sets for $5 to $15. You can also buy individual keys if you know your size. Some plumbing supply stores sell disposal-specific hex keys, though a standard set works just as well.