Water backs up into the opposite sink bowl when disposal runs (double sink)

Safety first: Turn OFF and unplug the disposal.

• Check for clogs: Remove and clean the P-trap and cross-over pipe between the two sink bowls. Clear any food or grease buildup.
• Verify drain slope: Ensure the disposal discharge and pipes slope downward toward the wall drain, not back toward the other bowl.
• Use a sink plunger: Plug one sink drain while plunging the other to clear minor clogs (disposal OFF).
• Inspect dishwasher hose routing: Ensure the dishwasher drain hose has a high loop or air gap to prevent backflow into the sink.
• If backups persist: The main drain line may be restricted; use a drain snake or call a plumber.