If your sink makes gurgling or bubbling noises when it drains — or when nearby fixtures are used — it’s usually a sign that air is moving through the plumbing system where it shouldn’t. Gurgling isn’t normal and often points to a developing drainage or venting issue.
In many cases, this starts as a minor problem and gets worse if ignored.
Quick Answer:
A sink gurgles because air is being pulled through the drain due to a partial clog, restricted drain line, or blocked plumbing vent. As water flows through the pipes, it displaces air, causing bubbling or gurgling sounds.
Why This Happens
Plumbing systems rely on proper airflow to allow water to drain smoothly. When airflow is restricted, air looks for the easiest exit — often through a sink drain.
Common causes include:
- Partial clogs in the sink drain or P-trap
- Buildup further down the drain line
- Blocked or restricted vent pipes
- Shared drain lines with other fixtures
- Improper drainage slope
A gurgling sink often appears alongside a sink that drains slowly, even if the sink doesn’t fully back up.
Step-by-Step: How to Diagnose Sink Gurgling
Step 1: Note When the Gurgling Occurs
Pay attention to timing.
Gurgling may happen:
- As the sink drains
- When nearby sinks or tubs drain
- When appliances discharge water
If the sink gurgles when other fixtures run, the issue may extend beyond the sink itself.
Step 2: Check Drain Speed
Run water in the sink and observe how it drains.
Signs of a problem include:
- Slow drainage
- Water pooling before draining
- Bubbling sounds during drainage
These signs suggest restricted flow or trapped air.
Step 3: Try Plunging the Sink
Use a flat-bottom sink plunger.
- Cover the overflow opening if present
- Add enough water to cover the plunger cup
- Apply several firm plunges
Plunging can clear partial blockages that cause gurgling.
Step 4: Inspect and Clean the P-Trap
Gurgling is often caused by buildup in the P-trap.
- Place a bucket underneath
- Remove the trap carefully
- Clean out debris and residue
- Reinstall and test
This step resolves many gurgling issues.
Step 5: Consider Venting Problems
If gurgling continues after clearing the trap, the issue may involve the plumbing vent.
Vent problems often cause:
- Gurgling noises
- Slow drainage
- Sewer smells
These issues frequently affect more than one fixture.
What Not to Do
- Don’t ignore recurring gurgling sounds
- Don’t keep running water to “push it through”
- Don’t pour chemical drain cleaners into the sink
- Don’t assume gurgling is harmless
Airflow issues often worsen over time.
When to Call a Professional
Call a plumber if:
- Gurgling persists after cleaning the P-trap
- Multiple sinks or drains are affected
- You notice sewer odors
- Drainage worsens or backs up
These signs often point to vent or main drain restrictions.
Safety Notes
- Avoid splashing dirty drain water
- Wear gloves when handling plumbing parts
- Tighten fittings gently to prevent leaks
- Stop using the sink if backups begin
Common Homeowner Questions
Is sink gurgling dangerous?
Not immediately, but it can indicate a blockage that could lead to backups.
Why does my sink gurgle when another sink drains?
Both fixtures may share a drain or vent, causing air to be displaced improperly.
Will plunging fix gurgling permanently?
Sometimes. If gurgling returns, deeper buildup or vent issues are likely.