Dual-Tub Kitchen Sink Backing Up (Both Sides)

What you’ll likely need

• Bucket + old towels
• Slip-joint pliers (or channel locks)
• Sink plunger (flat-bottom style)
• Drain snake (hand auger, 1/4" or 5/16")
• Gloves

Visual references

Step-by-step fix (best mechanical order)

1. Stop using the sink. Don’t run the disposal repeatedly. Bail out standing water into a bucket if needed.
2. Quick disposal check (if you have one):
   • Run cold water and the disposal for 10–15 seconds.
   • If it only hums / won’t spin, turn power off and free it (most have a hex key socket on the bottom).
3. Clean the P-trap.
   • Put a bucket directly under the trap.
   • Loosen the slip nuts, remove the U-bend, and clear out sludge/food.
   • Reassemble and test.
   If the trap is mostly clean and the sink still backs up, the clog is likely in the wall drain / horizontal run.
4. Plunge correctly for a double sink.
   • Plug the other bowl tightly with a stopper or a wet rag.
   • Put a few inches of water in the bowl you’re plunging.
   • Plunge hard 15–20 times, then repeat on the other side.
5. Snake the drain (most effective next step).
   • Remove the P-trap again.
   • Insert the snake into the wall stub-out (not just the disposal branch).
   • Feed 3–10+ feet, rotate as you go, retrieve debris, repeat until the line feels clear.
   • Reassemble and flush with hot (not boiling) water.
6. Confirm whether it’s bigger than the sink line.
   • If nearby fixtures (bathroom sink/tub) also gurgle or drain slowly, you may have a main line issue.
   • If only this sink is affected, it’s likely localized grease/food buildup in the kitchen branch.

Don’t do these

When it’s time to call a plumber

• You can’t clear it with a snake (or it repeatedly returns within days).
• Multiple fixtures are backing up (possible main line obstruction).
• You suspect old cast iron with heavy scale or a collapsed line.