In this case the problem is not in the disposal. The problem is a clog in the drain line.
Absolutely do not put any chemical drain cleaners in the sink. Chemical drain cleaners will adversely react with the pot metal housings of disposals, and in a worst case scenario they can actually chemically eat through the metal rendering the entire disposal useless.
If you have a double sink you might try plunging the opposite sink while the disposal is running. If that does not resolve the problem or if this disposal is mounted on a single sink you will need to check the traps, connections or the drain line under the sink.
The first step is to get a bucket and a small plastic container and dip as much of the standing water out of the sink as you can.
Next, Locate the P-trap under the sink. Place a bucket or other suitable container that will hold at least 2 gallons and place it under the P-trap. Now disconnect the P-trap and the standing water in the pipe should drain into the container.
Visually inspect the inside of the P-trap to insure their is no foreign object or debris clogged up in there.
If this is a double sink you will note a TEE connection where the pipes from either sink meet. Inside of that Tee there is a baffle and that is a common point of clogs. Remove the Tee and clean the inside, then reset the Tee.
If you found debris in either the TEE or the P-trap you may have found the problem. Reconnect the pipes and try running some water in the sink to see if the drain is clear. If not, you will need to once again dip the water out and put a container under the P-trap once again while you dis-assemble the P-trap. You will need to remove the tailpiece of the P-trap from the trap adapter on the drain pipe entering the wall, then snake the drain through the Trap adapter.
