Why Does My Washing Machine Smell Like Sewage?

Separate washer residue from a standpipe, trap or drain-vent problem.

Updated September 15, 2026Safety-aware troubleshootingNo professional inspection implied

Quick answerWhen a washing machine smells like sewage, first identify whether the odor is inside the drum or strongest behind the machine at the drain hose/standpipe. Odor that surges while the washer drains points more strongly toward the drain connection, trap or venting than to dirty laundry alone.

Safety / escalation noteStop and get plumbing help if the standpipe overflows, wastewater backs up, or several drains gurgle when the washer pumps out.

60-second diagnosis

Is the smell strongest inside the drum or behind the washer?
Does it spike during the drain/pump-out stage?
Does the standpipe overflow or sound like it is gulping?
Is the drain hose shoved unusually deep into the standpipe?
Do nearby sinks or floor drains gurgle during washer discharge?

Likely causes, ranked by fit

Standpipe/trap odor pathway

Common

Best fit: Strongest behind washer; odor spikes during drain cycle.

How to check: Observe from a safe dry position whether odor/gurgling originates at the standpipe.

What fixes the source: Plumber corrects missing/dry trap, standpipe or venting issues as needed.

Drain restriction

Common

Best fit: Standpipe rises, overflows or drains slowly when pump discharges.

How to check: Watch one drain cycle; stop if overflow begins.

What fixes the source: Clear/repair the laundry drain professionally if needed.

Washer biofilm / stagnant residue

Common look-alike

Best fit: Odor is strongest inside drum/gasket and persists even when drain is not active.

How to check: Inspect gasket, detergent drawer and filter locations per manufacturer instructions.

What fixes the source: Clean manufacturer-approved accessible areas and use correct detergent amounts.

Improper hose configuration

Possible

Best fit: Problem began after installation or moving the washer.

How to check: Compare drain-hose height/insertion with the manufacturer installation guide.

What fixes the source: Correct hose routing without making an airtight improvised seal.

What to do now

Smell-test the drum versus standpipe area.
Run one drain cycle while watching for gurgling or rise in the standpipe.
Clean the washer gasket/drawer/filter per manufacturer guidance if the drum itself is the source.
For a plumbing-pattern odor, fix the drain pathway rather than adding fragrance to the washer.

Do not do this

Do not seal the drain hose airtight with tape or foam unless the installation specifically requires an approved connection. Do not mix chlorine bleach with ammonia, acids or other cleaners.

When to call a professional

Call a plumber for standpipe overflow, missing trap/vent concerns or multi-fixture gurgling. Call appliance service if the machine has internal drainage faults or leaks.

Questions people ask

Why does the smell happen only when the washer drains?

That timing points toward the standpipe, trap, blockage or venting because the pump-out is when the drain system is heavily loaded.

Can a dirty washer smell like sewage?

Yes, concentrated biofilm and stagnant residue can smell foul. The location test — drum versus standpipe — helps separate appliance cleaning from plumbing work.

Should the drain hose be sealed into the pipe?

Washer drains are commonly designed with an air gap/open standpipe arrangement. Follow the machine and local plumbing requirements rather than improvising an airtight seal.

Source note

This guide uses general household troubleshooting logic. It does not claim a professional inspection, laboratory result or code determination. Safety-critical topics link to primary sources where relevant.

This information is educational and cannot verify a leak, electrical fault, mold condition, water quality result, plumbing-code issue or appliance failure remotely. When there is immediate danger, follow local emergency guidance.