Quick Answer:
If one sink bowl gurgles when you run the other, it usually means air is being pulled through the shared drain system because of a partial blockage or a venting issue. Start by listening for air movement and check for slow drainage in both bowls. Simple tests and basic clearing often fix it; call a plumber if the sound continues or drains back up.
Why This Happens
Most double-bowl sinks share the same trap and branch drain. When you run water in one bowl the moving water can create a vacuum or pressure change that pulls air through the other bowl’s drain. Common causes:
- Partial blockage in a trap or the branch line that slows flow and forces air to move.
- Poor venting that can’t equalize pressure quickly.
- Cross-connections created after work on the sink or disposal—this can be a reason to check Cross-flow after remodel.
- When a disposal is running it can create unusual flow patterns—see Cross-flow when grinding food.
Step-by-Step What to Do
1. Listen and check for air movement
- Run water in one bowl and put your ear close to the unused drain. Note whether you hear active air movement (a whoosh or suction) versus a simple bubbling sound.
- Gurgling with noticeable airflow suggests air is moving through the drain system rather than a simple splash noise.
2. Check for slow drainage in both bowls
- Fill each bowl with a small amount of water and release it. Time how fast the water disappears. Slow drainage in either bowl points to a partial blockage downstream or in the trap.
- If both bowls drain slowly, the problem is likely in the shared branch or main line rather than in a single trap.
3. Clear visible debris and test the disposal
- Remove and clean strainers or stoppers. Turn the disposal off at the switch and power source before checking it.
- Run cold water and briefly turn the disposal on to see if the sound changes. If gurgling appears only when grinding, that suggests a disposal-related flow problem.
4. Try simple clearing methods
- Use a sink plunger on each bowl (one at a time) to try to dislodge soft clogs. Seal the other drain while you plunge for better pressure.
- If comfortable, detach and inspect the P-trap for debris. Have a bucket ready for water.
5. Re-test and observe
- After clearing, run water in each bowl again and listen. If the gurgling is gone and drainage is back to normal, the issue was likely a blockage you removed.
- If gurgling persists or you notice sewage smells or backups, stop and consider calling a professional.
What Not to Do
- Do not block vents while testing. Covering vents or drains to force a result can hide the real problem and create unsafe pressure conditions.
- Do not keep using harsh chemical drain cleaners repeatedly. They can damage pipes and make future repairs harder.
- Do not work on the disposal or plumbing without turning power and water off if you are unsure of what to do.
When to Call a Professional
- The gurgling continues after basic clearing and both bowls still drain slowly.
- Multiple fixtures (toilet, other sinks) are slow or bubbling—this suggests a deeper blockage or venting failure.
- You smell sewage or see water backing up into the sink or other drains.
- You’re not comfortable removing the trap or accessing the branch line; a licensed plumber can inspect vents, run a camera, and make safe repairs.
Safety Notes
- Wear gloves and eye protection when clearing traps or using a plunger.
- Turn off electrical power to a garbage disposal before working on it.
- Avoid mixing chemical cleaners. If you’ve used a chemical cleaner, wait and ventilate the area before attempting mechanical cleaning.
Common Homeowner Questions
- Does the air moving through the drain mean a leak? Not usually; it typically means airflow from pressure changes, not a water leak.
- Can I fix this myself? Sometimes — plunging, cleaning strainers, and clearing the P-trap often help. Call a plumber if it persists.
- Will running the disposal make it worse? It can reveal existing problems; if gurgling happens only with the disposal, stop use and investigate.