Water backs up into the opposite sink bowl when using the garbage disposal

Safety first: Turn OFF power to the disposal before disassembling any plumbing.

• Step 1 – Run disposal and observe: With water running, operate the disposal and watch the opposite sink bowl. If water backs up there, the blockage is in the shared drain piping, not the disposal itself.
• Step 2 – Clean cross tube and tee: Remove the cross tube and baffle tee between the two sink bowls and clear any food or grease buildup.
• Step 3 – Clean P-trap: Remove and clean the P-trap and horizontal drain arm to the wall.
• Step 4 – Reassemble with proper slope: Ensure the cross tube and drain pipes have a slight downward slope toward the wall drain to prevent backflow.

Warning: Do not rely on chemical drain cleaners; mechanical cleaning is safer and more effective.