Garbage disposal makes a rhythmic knocking noise during operation, in time with the rotation.

Safety first: Turn off power and ensure the unit cannot start.

• Inspect chamber: Use a torch to look for foreign objects or visible bending of the impeller lugs.
• Remove debris: Extract any stones, bones, or hard fragments with pliers.
• Check lug movement: Gently move each lug with a wooden tool. If one appears bent or contacts the shredder ring, the grinding assembly is damaged.
• Replace assembly/unit: Because the impeller and ring are integral, replacement of the disposal is usually required to eliminate the knocking and prevent further damage.