Disposal runs but water backs up into sink; some smart sink control kits may show E4 indicating drain restriction or discharge fault.

Safety first: Turn OFF the disposal switch and unplug the unit or shut off the breaker. Do not use chemical drain cleaners in a disposal-equipped sink.

• Check for standing water: If water is standing in the sink, bail out as much as possible before disassembly.
• Inspect disposal outlet: Disconnect the discharge tube from the side of the American Standard disposal. Check for packed food debris at the outlet and clear it with a small brush or plastic tool.
• Clean the P-trap: Place a bucket under the trap. Loosen the slip nuts and remove the P-trap and trap arm. Clear any sludge or food buildup and rinse thoroughly.
• Dishwasher knockout: If a dishwasher is connected and not draining, confirm the metal/plastic knockout plug inside the dishwasher inlet on the disposal has been removed. If still present, carefully knock it out with a screwdriver and hammer (with power OFF) and remove the loose piece.
• Reassemble and test: Reinstall the trap and discharge tube, ensuring gaskets are seated. Run water and briefly operate the disposal to confirm proper drainage.