Disposal runs but water backs up into the dishwasher or leaks from the dishwasher hose connection; LED flashes once-long, three-short.

Safety first: Turn off power to the disposal and dishwasher. Do not run either appliance while the hose is disconnected.

• Check the dishwasher inlet: If the McAlpine disposal is newly installed, confirm that the plastic knockout plug inside the dishwasher inlet spigot has been fully removed. Use a screwdriver and hammer to knock it out, then retrieve the plug from the grinding chamber.
• Clean the inlet spigot: Remove the dishwasher hose and clear any food debris from the spigot. Rinse thoroughly.
• Inspect and reposition hose: Ensure the dishwasher drain hose has a high loop above the sink level to prevent backflow and is not kinked.
• Secure the clamp: Reattach the hose to the spigot and tighten the hose clamp firmly.