Quick Answer:
If you hear gurgling when the washer empties, run a washer drain cycle and watch the sink trap for bubbles. That test tells you whether the washer’s large discharge is pushing air through the trap or whether a vent or drain restriction is causing pressure changes. Often the problem is a blocked vent or a partial clog downstream, not the washer itself.
Why This Happens
- Washer discharge is fast and large. A quick rush of water can push air and water around in a shared drain line, which makes air move through the sink trap and causes gurgling.
- Partial blockages downstream slow water flow and let air back up through nearby traps.
- Venting issues: if the vent stack is blocked or poorly sized, the system can’t equalize pressure, so water movement draws air through traps.
- Improper trap or connection work: a misinstalled trap or too-short trap arm can let air move where it shouldn’t. If this started after changing plumbing parts, check the installation—see **Gurgling started after replacing P-trap** for related situations.
- If the noise only appears on one floor or in certain fixtures, the problem may be venting or a shared line serving that area—compare notes with **Sink gurgles only upstairs**.
Step-by-Step What to Do
1. Prepare the area
- Clear under the sink and set a bucket or towels ready in case you need to catch water when you inspect the trap.
- Have a flashlight so you can see into the trap and drain opening.
2. Run the washer drain cycle and observe
- Start a drain/spin cycle on the washer while someone watches the sink trap or the sink bowl. Watch for bubbles, splashing, or water level changes in the trap.
- If you see steady, forceful bubbles or the trap water level drop, that shows air or water from the washer is affecting the trap.
3. Check other fixtures
- Run water in nearby sinks, tubs, or floor drains. If multiple fixtures gurgle or slow at the same time, the problem is likely in the shared drain or vent, not the washer alone.
4. Inspect and clear the sink trap
- If the trap looks dirty or partially blocked, put the bucket underneath, loosen the trap slip nuts, and clean it out. Reassemble snugly (don’t overtighten).
- Then rerun the washer drain test to see if the gurgling stops.
5. Check venting and downstream lines
- Listen at the roof vent (from the attic or roof) when the washer drains. A blocked vent or an animal nest can cause the symptoms. Don’t climb a roof if you are not comfortable; call a pro for a safe inspection.
- If you suspect a downstream clog, a drain snake through the sink or the washer standpipe can help. If a long snake or machine is needed, hire a plumber.
6. Re-test and document
- After each simple fix (trap clean, plunger, or small snake), run the washer drain again and note any change. If the gurgle persists, move to the next step or call a professional.
What Not to Do
- Do not assume washer discharge is the only cause without checking venting.
- Don’t pour strong caustic drain cleaners into a trap you plan to remove by hand—those chemicals can burn skin and damage pipes.
- Don’t climb onto a roof to clear a vent unless you have safe ladder skills and fall protection. Call a professional if you are unsure.
- Don’t force a long snake through tight P-trap connections; that can damage fittings. Disconnect and clean traps first, then snake further if needed.
When to Call a Professional
- The gurgling continues after you’ve cleaned the trap and tested the washer drain.
- Multiple fixtures gurgle, back up, or drain slowly at the same time.
- You smell sewer gas or you have repeated backups. These can indicate a serious vent or mainline problem.
- You suspect a blocked vent high on the roof or in the attic and you’re not comfortable or safe inspecting it yourself.
Safety Notes
- Turn off and unplug appliances before working nearby to avoid electrical hazards.
- Wear gloves and eye protection when handling traps and debris.
- Use a stable ladder and proper footing if you must inspect a roof vent; otherwise hire a pro.
- Avoid mixing chemical drain cleaners with other cleaners and do not use them before physically cleaning the trap if you plan to touch it.
Common Homeowner Questions
- Will running the washer make the problem worse? No — running the washer is a useful test to see how the system behaves; it won’t cause new damage if the drain is functioning.
- Can a clogged vent cause gurgling? Yes — a blocked vent can prevent pressure equalization and let air move through traps, causing gurgling.
- Can I fix this with a snake? Sometimes — a handheld snake can clear trap or nearby line clogs, but deeper or mainline issues usually need a professional.