Washing machine smells musty or moldy

Q: Washing machine smells musty or moldy

In Canada, when a front-loading washer smells musty or moldy, the most common cause to rule out is mildew and biofilm hiding in the folds of the rubber door gasket (the bellows) and the detergent drawer, because HE machines here run cold cycles that never get hot enough to kill it. Wipe the gasket, clean the drawer, and leave the door ajar between loads. Using too much detergent or a non-HE soap, and never running a hot clean-washer cycle, let that buildup grow. A clogged drain pump filter can hold stagnant water and lint. A smell like sewage rather than mildew usually comes from the drain plumbing, not the machine — that's a plumber's call.

A washer that smells is annoying, not broken — and the fix is almost always cleaning, not repair. Most of the time it's mildew hiding in the rubber door seal.

tuneWhat are you noticing?

Select anything that matches and the checklist below reorders to fit. Not sure? Skip it.

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Start here

In Canada, start at the rubber door gasket on a front-loader. Peel back the folds with a flashlight and look and sniff: black speckled gunk and a musty smell there is the number-one cause of a smelly washer. Check the detergent drawer the same way. Both are free to inspect and clean by hand.

Ranked from real-world failure data. The order updates as you select what you’re noticing above.

Likely causes, in the order to check them

Showing the typical order

Beginner-friendly Doable, with care Safety-critical Call a pro

handymanHow to fix it

Wipe out the folds of the rubber door gasket with a mild cleaner, pull and wash the detergent drawer, dry both, and get in the habit of leaving the door and drawer ajar between loads so the drum can breathe and dry.

Peel back each fold of the rubber door gasket and wipe out the black gunk with a cloth dampened in warm soapy water or a 50/50 white-vinegar solution. Get right into the bottom of the fold where water pools.
Pull the detergent drawer fully out (most release with a tab or press-point), and scrub it and its cavity with an old toothbrush to clear the slimy soap-and-softener buildup.
Dry the gasket and drawer with a towel. Avoid bleach on rubber unless the manufacturer says it's safe — it can dry out and crack the bellows.
From now on, leave the door and the detergent drawer open a crack between loads so the inside dries out instead of staying damp and dark.

schedule20 min savings$5–15

gavel Check your province first AB: homeowner may do this · BC: homeowner may do this · ON: homeowner may do this · PE: homeowner may do this · QC: homeowner may do this
Cleaning the door gasket and detergent drawer is routine homeowner maintenance in every province.

handymanHow to fix it

Run the machine empty on its hottest cycle (or the dedicated tub-clean / self-clean cycle) with a washer-cleaning tablet or white vinegar to strip the built-up film, then wipe the drum and leave the door open to dry.

Empty the drum completely — no clothes. Add a washer-cleaning tablet, or about two cups of white vinegar in the drum, following the cleaner's directions.
Select the tub-clean / self-clean cycle if your machine has one, or otherwise the hottest, longest cycle. Let it run to the end.
When it finishes, wipe the drum and the gasket dry and leave the door open. Make this a monthly habit in a household that washes mostly cold.

schedule90 min savings$5–20

Washing machine cleaner (tablets) or white vinegarAffresh-type HE washer tablets, or plain white vinegar; both widely stocked at Canadian grocery and hardware stores

visibilityHow to check the drain pump filter

warning Unplug it, and expect trapped waterThe drain pump filter sits low near the machine's power and pump, and it holds a pocket of water even when the drum looks empty. Always pull the plug before you open it, and open the cap slowly over a towel and pan so it drains in a controlled trickle rather than a gush. If the machine has run a hot cycle recently the water can be hot enough to scald — let it cool. If reaching or opening the trap is awkward, this is a quick job for an appliance technician.

Unplug the washer at the wall first — you'll be opening a part that holds water near the machine's wiring.
Find the small access door low on the front corner and pop it open. Lay a folded towel down and slide a shallow pan under the filter cap to catch the water.
Turn the cap a quarter turn and let the water trickle out in a controlled stream. Dark, foul, slimy water and packed lint confirm the trap as a smell source; clean, clear water points you back to the gasket and drawer instead.

buildNo tools schedule15 min

handymanHow to fix it

With the washer unplugged, drain and remove the drain pump filter over a towel and pan, clear out the lint, hair, and any coins, rinse the filter and its housing, then reseat it snugly and run a short rinse to check for leaks.

Confirm the washer is unplugged. Open the access door, set a towel and shallow pan underneath, and drain the trap by cracking the cap open slowly.
Unscrew the filter the rest of the way and pull it out. Clear the lint, hair, and debris, and check the empty housing with a flashlight for anything stuck in the impeller behind it.
Rinse the filter under the tap and wipe the housing clean. Reseat the filter and thread the cap firmly — most have an arrow or lock mark for the closed position — so it seals.
Close the access door, plug the washer back in, and run a short rinse cycle. Watch the trap door for any drips; a slow leak means the cap isn't fully seated.

schedule25 min savings$0–5

gavel Check your province first AB: homeowner may do this · BC: homeowner may do this · ON: homeowner may do this · PE: homeowner may do this · QC: homeowner may do this
Cleaning the drain pump filter is routine homeowner maintenance; no permit or licence is required.

handymanHow to fix it

Rule out a dried-out trap by running a rinse to refill it, and check that the drain hose sits only a few centimetres into the standpipe with an air gap around it rather than jammed to the bottom. If a sewage smell keeps returning, the standpipe, trap, or venting needs a licensed plumber.

If the washer sits unused for stretches, the trap in the drain can dry out and let sewer gas up. Run a rinse or pour a litre of water down the standpipe to refill the trap and see if the smell clears.
Check the drain hose: it should sit only 10–15 cm into the standpipe with air space around it, not shoved to the bottom and sealed. A sealed connection can siphon the trap dry or push gas back into the room.
If refilling the trap and reseating the hose doesn't stop a returning sewage smell, stop here — a dry or missing trap, a venting fault, or a partly blocked drain is a licensed plumber's diagnosis, not a washer cleaning.

schedule15 min savingsusually free

warning A sewage smell is plumbing, not laundryIf the smell is sewage or rotten eggs rather than damp mildew, it is almost certainly the drain, not the washer — and no amount of cleaning the machine will fix it. Refilling a dried-out trap is a safe first try, but a smell that keeps returning points to a trap, vent, or standpipe problem. That is a licensed plumber's work, both because drain and vent plumbing is regulated in most provinces and because a persistent sewer-gas smell inside the home shouldn't be left unresolved.

gavel Check your province first AB: homeowner may do this · BC: permit + inspection required · ON: homeowner may do this · PE: homeowner may do this · QC: permit + inspection required
Refilling the trap and reseating the drain hose is DIY; modifying the standpipe, trap, or venting is a licensed plumber's job and may need a permit. Confirm local rules before any drain plumbing.

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Why the list is in this order

We don’t sort by likelihood alone. We sort the way a good, honest tradesperson thinks: rule out the free, safe, common causes first. That’s why the cheap checks outrank the expensive repairs — and why anything dangerous gets a hard stop instead of a pep talk. The order exists to save you money, not to sell you anything.