If your washing machine smells like sewage or rotten eggs, the odor is usually coming from bacteria buildup, stagnant water, or sewer gas backing up through the drain. While the smell may seem like it’s coming from the washer itself, the real source is often the drain system connected to it.
This issue is common in both front-load and top-load washers, especially if the machine isn’t used frequently or if the drain setup isn’t properly vented.
What a Sewage Smell Usually Means
A sewage-like odor typically indicates:
- bacteria growing in standing water,
- mold or sludge buildup in hoses or filters,
- sewer gas entering through the drain,
- or a dry or improperly installed drain trap.
These smells are unpleasant but usually fixable once the source is identified.
Common Causes of a Sewage Smell
1) Bacteria and Mold Buildup Inside the Washer
Soap residue, fabric softener, and moisture create an ideal environment for bacteria and mold.
More common when:
- using too much detergent,
- washing in cold water frequently,
- leaving the door or lid closed between loads.
Fix:
Run a hot cleaning cycle using a washer cleaner or white vinegar and baking soda (if manufacturer-approved). Leave the door open between washes to allow drying.
2) Standing Water in the Drain Pump or Filter
Water trapped in the pump or filter can stagnate and smell like sewage.
Clues:
- Smell worsens when the washer drains
- Odor strongest near the bottom front of the washer
Fix:
Clean the drain filter (front-load washers) and remove any debris or sludge.
3) Sewer Gas Entering Through the Drain Hose
If the washer’s drain hose is pushed too far into the standpipe or the plumbing trap is dry, sewer gas can escape into the washer and laundry area.
Fix:
Ensure the drain hose:
- is not sealed airtight,
- has an air gap,
- and is inserted no more than the recommended depth.
4) Clogged or Dirty Drain Hose
Lint, hair, and residue can collect inside the drain hose and cause foul odors.
Fix:
Flush or replace the drain hose if buildup is suspected.
5) Improper or Missing P-Trap
The P-trap is designed to hold water that blocks sewer gas. If it’s missing, dry, or improperly installed, odors can enter the washer.
Fix:
Run water down the drain to refill a dry trap, or have a plumber inspect the drain setup.
6) Laundry Room Plumbing Issues
Sometimes the smell isn’t the washer at all but nearby drains that release odor when the washer runs.
Fix:
Check floor drains, utility sinks, and nearby plumbing fixtures for dry traps or clogs.
What to Do If the Smell Is Strong
- Run a cleaning cycle immediately
- Clean the drain filter and gasket
- Check drain hose placement
- Ventilate the room
- Stop using the washer if sewer gas odor persists
Quick Troubleshooting Checklist
Before calling for service, try these basic steps:
- Run a hot washer-cleaning cycle
Use a washer cleaner or manufacturer-approved method. - Clean the drain filter
Remove debris and trapped water. - Inspect the door gasket or tub rim
Wipe away mold and residue. - Check drain hose installation
Make sure it’s not sealed or inserted too deeply. - Run water in nearby drains
This helps refill dry plumbing traps. - Leave the washer door open between loads
Allow moisture to evaporate.
When to Call a Professional
You should consider professional help if:
- the sewage smell persists after cleaning,
- sewer gas odor is strong or constant,
- multiple drains smell at the same time,
- or you suspect a plumbing vent or trap issue.
FAQ
Is a sewage smell from a washer dangerous?
It can be. Sewer gas exposure isn’t healthy, especially if the smell is strong or persistent. It should be addressed promptly.
Can detergent cause this smell?
Yes. Excess detergent contributes to residue buildup that feeds bacteria and mold.
Why does the smell come back after cleaning?
If the drain system or trap is the source, cleaning the washer alone won’t permanently fix the problem.