Why Does My Sink Gurgle When the Washing Machine Drains?
If your sink gurgles when the washing machine drains, it might catch you off guard. Everything seems to be working—your washer runs, the sink drains fine—yet there’s that unmistakable gurgling noise coming from the sink. This sound is more than just a harmless side effect of draining water. It’s usually a sign that your plumbing system is struggling to manage water flow and air pressure correctly.
Let’s take a closer look at why this happens, what it means for your plumbing, and when to take action.
The Plumbing Behind the Gurgle
Your home’s drainage system works through a combination of water flow, gravity, and ventilation. When your washing machine drains, it pushes a large volume of water into the pipes very quickly. If the system is functioning properly, this water flows smoothly through the drain lines and vents without affecting other fixtures.
But if there’s a problem—like a partial clog, vent blockage, or undersized pipe—the surge of water creates pressure and turbulence. This pressure may force air to escape through the path of least resistance: your sink drain, which results in that gurgling or bubbling sound.
Common Reasons a Sink Gurgles During Washer Drainage
- Shared Drain Line
In many homes, the washing machine and sink share the same horizontal drain pipe. If that pipe is partially blocked or not sloped properly, water from the washer can displace air and force it back through the sink trap—causing the gurgle.
- Clogged or Blocked Vent Pipe
Vents allow air to enter the plumbing system so water can drain freely. If the vent pipe is clogged with debris or blocked at the roof level, pressure can’t equalize. The result? A vacuum effect that pulls air through your sink trap as the washer drains.
- Insufficient Pipe Diameter
Older homes or DIY plumbing setups may have undersized pipes that can’t handle the sudden volume of water from a modern washing machine. This can create backflow pressure that manifests as gurgling sounds in nearby sinks.
- Failing Air Admittance Valve (AAV)
If your system uses an AAV instead of a full vent, a stuck or broken valve can’t admit the air needed during drainage. This can cause similar symptoms as a clogged vent pipe.
Is a Gurgling Sink a Serious Problem?
A sink that gurgles when the washer drains might not be an emergency, but it’s a red flag. Even if water still flows normally, the gurgling noise suggests that:
- Pressure isn’t being properly regulated in your plumbing
- There may be partial blockages in shared drain lines
- Sewer gases could enter your home if traps are compromised
- Your system is under long-term strain that can cause damage over time
Ignoring these sounds can lead to clogged drains, backups, or costly pipe repairs later on.
What You Can Try
Before calling a plumber, here are a few things you can check:
- Run hot water through the sink to clear minor buildup
- Flush the washing machine drain with a safe enzyme cleaner
- Inspect the roof vent, if accessible, for visible obstructions
- Ensure the sink trap has water and is properly sealed
- If you have an AAV, check that it opens and closes smoothly
However, since most causes involve deeper parts of the drainage or venting system, these steps may not solve the issue entirely.
When to Call Fly Plumbing
If your sink gurgles every time your washer drains, especially if it’s getting louder or more frequent, it’s time for a professional inspection. At Fly Plumbing, we use camera diagnostics and vent testing to pinpoint the exact cause—whether it’s a shared line issue, vent problem, or a deeper clog in the main drain.
We’ll restore proper flow, reduce pressure buildup, and make sure your sink and washing machine can operate together without creating plumbing stress.
Don’t ignore the noise—let Fly Plumbing handle it before it becomes a bigger (and costlier) issue.
Frequently Asked Questions
Why does my sink gurgle when my washing machine drains?
This usually happens when the sink and washer share a drain or vent. Rapid drainage from the washer creates air pressure changes that force air through the sink trap, causing a gurgling noise.
Is it a serious problem if my sink gurgles during washer drainage?
It can be. Gurgling may indicate a developing clog, poor venting, or undersized pipes. These issues can lead to slow drainage, sewer gas, or even backups if not addressed.
Can I fix a gurgling sink myself?
You can try flushing the drain with hot water, checking your air admittance valve, or inspecting accessible vents. But if the noise persists, it’s best to have a plumber evaluate the system.
