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 (Allen wrench) to manually turn the grinding chamber when the unit jams. Some models use 3/32 inch or 5/32 inch instead. The size you need depends on the hex socket built into the bottom of your disposal — there is no universal standard across manufacturers.

The hex socket sits on the underside of the disposal housing, directly below the grinding chamber. When food or a foreign object locks the blades, you insert the Allen wrench into this socket and turn it back and forth to free the jam. Using the wrong size will either not fit or will slip inside the socket without gripping, leaving you unable to turn the chamber.

If you do not know your disposal's model number, the fastest way to find the correct size is to measure the hex socket opening itself with a ruler or caliper, or to call the manufacturer with your model number and ask directly.

Key Takeaways

  • The 1/8 inch Allen wrench fits most common garbage disposal models, including InSinkErator and Waste King units.
  • The hex socket is located on the bottom center of the disposal housing and is the only place an Allen wrench should be inserted.
  • Using the wrong size will not grip the socket properly and may damage the wrench or the socket itself.
  • Your disposal's manual or manufacturer's website will list the correct size if 1/8 inch does not fit.

How to identify the socket size without the manual

If you have lost the manual or do not have the model number handy, you can measure the hex socket opening directly. Place a ruler or measuring tape against the flat sides of the socket opening — measure from one flat edge to the opposite flat edge across the widest point. This measurement tells you the width of the socket.

Common sizes are 1/8 inch (3.175 mm), 3/32 inch (2.38 mm), and 5/32 inch (3.97 mm). If your measurement falls between two sizes, round down and test the smaller wrench first — it is easier to confirm a poor fit than to force a wrench that is too large into the socket.

Another approach is to visit a hardware store with a set of hex keys and try each size against the socket opening while the disposal is off and unplugged. The correct size will slide in smoothly with no wobble and will grip firmly when you turn it.

Common disposal models and their hex key sizes

InSinkErator disposals, which account for roughly half the residential market, typically use 1/8 inch. Models like the Evolution, Badger, and Food Chief series all use this size. Some older InSinkErator units use 3/32 inch, so check your manual if 1/8 inch does not fit.

Waste King disposals also standardize on 1/8 inch for most residential models, including the Legend and Powerhouse lines. Moen disposals typically use 1/8 inch as well. Kohler disposals vary — some use 1/8 inch and others use 5/32 inch, so verification is important before you buy.

If your disposal is a less common brand or an older model, the manufacturer's website or a call to their customer service line is the most reliable way to confirm. Many manufacturers list the hex key size in the troubleshooting section of their online manuals.

Where the hex socket is located and how to use it safely

The hex socket is always on the bottom of the disposal unit, centered underneath the grinding chamber. You will see a small hexagonal opening in the metal housing. Never attempt to insert an Allen wrench into the top of the disposal or into the drain opening — this will not work and may damage the unit or injure your hand.

Before you insert the wrench, turn off the disposal and unplug it from the outlet. If the disposal is hardwired (no plug), turn off the circuit breaker that controls it. Wait at least five minutes to may support the blades have stopped spinning completely. Insert the Allen wrench into the hex socket and turn it gently back and forth — do not force it. A few quarter-turns in each direction are usually enough to break the jam free.

Once the chamber turns freely, remove the wrench, plug the disposal back in, and run cold water while you turn it on briefly to flush out any remaining debris. If the wrench does not fit or does not grip, stop when ready and do not force it — you may have the wrong size, and forcing it can strip the socket.

What to do if you cannot find the right size

If you have tried the common sizes and none of them fit, contact the disposal manufacturer directly with your model number. You can usually find this on a label on the side or bottom of the unit, or in your purchase paperwork. Most manufacturers have a customer service phone line and will tell you the correct size within a few minutes.

If the disposal is very old or the manufacturer is no longer in business, a plumber can identify the size by inspection or can remove the jam using other methods. This is worth the cost if you cannot determine the size yourself, because using the wrong tool can damage the socket and make the disposal harder to service later.

Buying and storing the right Allen wrench

Once you know your size, buy a single Allen wrench in that size rather than a full set. A single 1/8 inch wrench costs two to four dollars at any hardware store and takes up almost no space. Keep it in a drawer near your kitchen or in a toolbox where you can find it quickly if the disposal jams.

Some people tape the wrench to the underside of the sink cabinet or to the disposal unit itself so it is always within reach. This is practical if you have a disposal that jams frequently, though it is not necessary for most households. A wrench stored in a nearby drawer is usually sufficient.

Frequently Asked Questions

Can I use a different size wrench if I do not have the exact one?

No. Using a wrench that is too small will slip inside the socket and may round out the edges, making it impossible to grip later. A wrench that is too large will not fit at all. Always use the exact size your disposal requires.

What if the hex socket is stripped and the wrench will not grip?

A stripped socket cannot be repaired with an Allen wrench. You will need to contact a plumber or the manufacturer for repair options, which may include replacing the disposal or the grinding chamber assembly. This is rare but can happen if the wrong size wrench was forced into the socket repeatedly.

Is it normal for a disposal to jam frequently?

Occasional jams are normal, but frequent jams suggest a problem with what you are putting down the drain. Avoid fibrous foods like celery and potato peels, and never put bones, glass, or metal in the disposal. If jams continue even with careful use, the disposal may need professional service or replacement.

Can I use a power drill with a hex bit instead of a manual wrench?

No. A power drill can turn too fast and too hard, potentially damaging the grinding chamber or the socket. Always use a manual Allen wrench so you can feel the resistance and stop if something does not turn freely.

Where can I buy an Allen wrench if I do not have one?

Hardware stores, home improvement stores, and online retailers all carry individual Allen wrenches in standard sizes. A single wrench costs between two and five dollars. If you need it when ready, a local hardware store is faster than shipping.