Water backs up into the dishwasher from the sink, especially when the garbage disposal is used.

Safety first: Turn off power and avoid running the dishwasher until corrected.

• Check sink drain: Clear any clogs in the sink or disposal. Run water and disposal to ensure free flow.
• Verify high loop: Ensure the dishwasher drain hose is routed up under the countertop before connecting to the sink or disposal.
• Install air gap (if required): In some areas, an air gap is required by code. Install one if missing and local codes demand it.

Repair action: Re-route the drain hose to create a proper high loop or install an air gap. This prevents sink water from siphoning back into the dishwasher.