Quick Answer:
If you smell sewer gas when the washer drains, it usually isn’t a broken washer but a problem with the drain connection or trap. First watch when the odor appears, then check the standpipe and P-trap for dryness, size, or leaks. A short vinegar rinse can remove trapped residues and help you pinpoint whether the smell comes from the plumbing or the machine.
Why This Happens
- Air pushed from the washer hose can travel back through a dry or improperly configured P-trap, letting sewer odors into the room.
- Cracked or loose drain hoses, or a poor tailpiece/air gap connection, let wastewater or smell escape during high-flow drain cycles.
- Residues and lint trapped in the standpipe or short sections of drain can create a persistent odor that releases when water rushes past. If you recently cleaned drains or added parts, this can look like a Smell after drain cleaning or a Smell after filter install situation.
Step-by-Step What to Do
1. Observe the timing of the smell
- Run a laundry cycle and note whether the odor appears only during the spin/drain stage or lingers afterward.
- If it smells only during draining, suspect backflow, siphoning, or a leak at the connection point. If the odor remains afterward, the trap may be dry or there may be residue in the standpipe.
2. Inspect the standpipe and P-trap
- Look into the standpipe (with the washer off). The trap should hold water—no dry, gurgling sound when water flows.
- Check for an undersized or incorrectly installed trap. Mis-sized traps or the absence of a proper trap can let sewer gas through or allow siphoning during drain cycles.
3. Check the tailpiece and air gap connection
- Examine the drain hose where it enters the standpipe or air gap for cracks, loose fittings, or a hose pushed too far down the pipe.
- Tighten any loose clamps and replace cracked hoses. Make sure the hose end sits properly—not jammed or dangling too deep into the standpipe.
4. Run a vinegar rinse and smell-test
- Run a rinse cycle with one cup of plain white vinegar in the drum. Vinegar helps dissolve residues and deodorizes without harsh chemicals.
- After the rinse, run a drain-only cycle and check whether the smell has reduced or gone. If the odor improves, trapped residues were likely the source.
5. Confirm standpipe height and trap configuration
- Ensure the standpipe and trap setup prevents siphoning. Standpipe height and trap layout need to follow local code so the drain can’t pull dry the trap during fast drains.
- If you’re unsure about the configuration or code requirements, get a qualified plumber to confirm the installation meets standards and to correct any siphon risk.
What Not to Do
- Do not stuff deodorizing pads or air fresheners into the standpipe—they can clog the drain and worsen problems.
- Avoid pouring heavy solvents or strong chemical cleaners down the washer drain; they can damage plumbing, seals, or septic systems.
- Don’t assume a persistent odor will go away on its own—call a pro when odors persist after cleaning the trap or if the washer repeatedly backs up or overflows.
When to Call a Professional
- Call a plumber if the smell continues after you’ve checked the trap, tightened or replaced hoses, and run a vinegar rinse.
- Get help if the washer backs up, overflows, or if you find a missing or badly damaged trap—these are signs the drain connection needs repair or reconfiguration.
- If you suspect sewer gas is entering the home through multiple drains or you detect gas in other rooms, call a professional promptly.
Safety Notes
- Turn off power to the washer and shut off the water supply before disconnecting hoses or working behind the machine.
- Ventilate the laundry area while testing and when odors are present. Open windows and doors if safe to do so.
- Wear gloves and eye protection if you handle hoses or clean the trap area. Never mix household chemicals—use plain white vinegar for rinse tests instead of strong cleaners.
Common Homeowner Questions
- Why does it only smell during the spin/drain? Because high flow can force air and odors past a poor seal or a dry/mis-sized trap.
- Is a cup of vinegar safe for my washer? Yes. A cup of plain white vinegar during a rinse is safe and helps remove residues without harming the machine.
- Can I fix a mis-sized trap myself? Possibly, if you’re comfortable with basic plumbing; otherwise hire a plumber to ensure the trap and standpipe meet code and prevent future problems.
More in this topic
For more related fixes and similar symptoms, see Sewer Gas Smell from Floor Drains.