Disposal runs but water backs up into sink; grinding seems normal but sink drains very slowly or not at all; some models may flash four times on internal LED.

Safety First: Turn OFF power to the disposal and do not operate it while the drain is disassembled. Never use chemical drain cleaners in or around the disposal.

• Step 1 – Verify disposal is grinding: If it sounds normal and water still backs up, the issue is likely in the drain piping, not the motor.
• Step 2 – Remove and clean the P-trap: Place a bucket under the trap. Loosen the slip nuts on the P-trap and discharge elbow from the disposal. Remove the trap and clean out any sludge or food buildup.
• Step 3 – Inspect the disposal discharge: Check the 1-1/2" discharge outlet on the side of the AmazonCommercial unit for hardened debris. Use a small brush or plastic tool to clear it.
• Step 4 – Check downstream piping: If the trap is clear, inspect the horizontal branch line going into the wall. Use a small drain snake if necessary.
• Step 5 – Reassemble and test: Reinstall the trap and fittings, ensuring gaskets are seated. Run water and briefly operate the disposal to confirm proper drainage.
• If multiple fixtures back up: The blockage may be in the main household drain; contact a plumber.