The short answer: the smell tells you where the problem is, and treating them all the same is why cleaning the machine so often changes nothing. Musty means mould and biofilm in the door seal, drum and detergent drawer. Sewage usually means a dry or blocked drain trap, and frequently not the washer’s trap but the floor drain nobody uses. Rotten eggs means hydrogen sulfide, which comes from bacteria, or from well water, or from a natural gas leak, because utilities add an odorant that smells of sulfur. If there are gas appliances near your laundry room and the smell is sulfurous, leave and call the gas company before you assume it is the washing machine.
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The one that means leave the house
Almost every article on this subject treats a rotten egg smell as a plumbing or bacteria problem, works through the causes, and gives you a cleaning routine. Only one of the sources I read mentions the possibility that should be ruled out first.
Natural gas has no smell of its own. Utilities add an odorant so that leaks can be detected, and that odorant smells of sulfur. Which is to say it smells like rotten eggs.
So if your laundry room has gas appliances nearby, a boiler, a gas dryer or a water heater, and you are smelling sulfur, the washing machine is not the first thing to investigate. Leave the house and call the gas company.
How to tell them apart
A washer smell is tied to the machine. It comes from the drum, the seal or the drain, it is strongest when you open the door or when the machine drains, and it does not follow you around the room.
A gas smell is in the air. It is not stronger at the machine, it is present whether the washer has run or not, and it may be stronger near an appliance or a pipe than near the washer.
If you are unsure which you have, treat it as gas. The cost of being wrong in that direction is a phone call.
And then the ordinary explanations
Once gas is ruled out, a rotten egg smell is hydrogen sulfide, which one appliance training source describes plainly as a gas commonly found in sewers and produced by bacterial metabolism.
It reaches your nose by one of three routes: bacteria living inside the machine, sewer gas coming up the drain, or the water supply itself, which matters if you are on a well.
Numbers worth knowing
There is a reason this problem is more common than it used to be, and it is not that machines got worse. Households have moved to lower wash temperatures and high-efficiency detergents, and both changes suit fabrics and energy bills while suiting bacteria rather well too. A cold wash does not kill what a hot one did, and residue accumulates where water no longer reaches temperature.
Front loaders are the most affected, because a horizontal drum needs a watertight door seal, and that seal is a fold that holds water, lint and detergent between loads. It is the single most common site of the musty version of this problem, and it is the one place people never look.
Which brings us to the three ordinary smells and where each of them lives.
Find the source in 3 taps
Which smell, when it appears, and what machine you have. Those three narrow it to one place before you clean anything.
The test that settles it in two minutes
Before cleaning anything, find out whether the smell is coming from the machine or arriving from the plumbing. An appliance training source gives the method and it is the most useful thing on this subject.
Smell the standpipe
Find where the washer’s drain hose goes. It will run into a standpipe, a vertical pipe usually behind or beside the machine, or into a utility sink.
Pull the hose out of the standpipe and smell the pipe itself.
If the standpipe smells, the problem is the plumbing and cleaning the washing machine will achieve nothing. If the standpipe is fine and the machine smells, the problem is inside the machine.
That single check saves an evening of scrubbing a drum that was never the issue.
Two more that narrow it further
Does it only smell while draining? Then it is biofilm. Water passing over the coated surfaces disturbs the film and releases the odour, which is why a machine can seem fine sitting idle and turn unpleasant the moment it empties.
Does water from another tap smell too? Then it is the supply, not the appliance. This matters mainly on well water, which frequently contains hydrogen sulfide, and no washer cleaner addresses a water problem.
The dry trap, and why it is usually the floor drain
If the standpipe smells, the most common cause is a dry P-trap. Every drain has a U-bend that holds a little standing water, and that water is a seal blocking sewer gas from coming up the pipe. When a drain goes unused for a few weeks, the water evaporates and the seal is gone.
And the culprit is frequently the floor drain rather than the washer’s own trap, for a reason that is obvious once stated: the washer drains into a standpipe, so the floor drain in the same room never gets used and its trap dries out on its own.
The fix is a gallon of water poured down it, which takes a minute. Then do it every few weeks on any drain you rarely use.
When water does not fix it
If the trap is wet and the smell persists, the possibilities are a partial blockage in the line where lint, hair and soap have caught and bacteria are growing on it, a clogged vent pipe, or a drain hose installed at the wrong height so dirty water sits in it. The first two want a plumber rather than a DIY attempt. The third you can check yourself: look for kinks, sagging sections and whether the hose sits at the height the manufacturer specifies.
Four smells, four places
Naming the smell is the fastest route to the fix, because each one comes from somewhere different.
| Smell | Where it comes from | First thing to do |
|---|---|---|
| Musty, damp | Mould and biofilm in the door seal, drum and drawer | Fold back the seal and look inside it |
| Sewage | Dry or blocked drain trap, often the floor drain | Pour a gallon of water down every drain in the room |
| Rotten eggs | Bacteria, well water, or a gas leak | Rule out gas first if there are gas appliances |
| Burning or hot plastic | Mechanical or electrical fault | Stop using it. Unplug it. Get it looked at |
| Stagnant water | Machine not draining fully, water sitting in hose or pump | Check the drain hose for kinks and the filter for blockage |
The third row is the one worth reading twice. Utilities add an odorant to natural gas precisely so leaks can be smelled, and that odorant is sulfurous. So a rotten egg smell in a room with a gas boiler, a gas dryer or a gas water heater is a possible leak until proven otherwise, and no amount of appliance knowledge changes that.
And the fourth row exists because a burning smell gets grouped with the others in most articles and it does not belong there. It is not something to clean, it is something to stop using.
Numbers worth knowing
Biofilm settles into three places, and people clean one of them. The drum is obvious, the rubber door seal is the one everybody eventually learns about, and the detergent drawer is the one almost nobody touches, because it sits damp between loads and does not rinse itself clean. Most dispensers pull fully out with a release tab. Soak it in hot soapy water for an hour, and while it soaks, scrub the cavity it came out of with a bottle brush.
The fourth place is the drain pump filter, usually behind a small hatch at the bottom front of a front loader. Cleaning it monthly is standard manufacturer advice and almost nobody does it, partly because most people do not know it exists. Put a towel and a shallow tray underneath before you open it, because there will be water.
The clean, and the habits that keep it clean
Assuming the standpipe test pointed at the machine rather than the plumbing.
- Fold the door seal back and clean inside the fold. On a front loader this is where the problem usually is. Expect black speckling, lint, hair and the occasional sock. Wipe it with hot soapy water or a dilute vinegar solution, working all the way round.
- Pull the detergent drawer right out and soak it. An hour in hot soapy water softens hardened detergent. Scrub the cavity behind it with a bottle brush or a pipe cleaner, including the water jets at the top.
- Clean the drain pump filter. Towel and tray underneath, unscrew the cap, let it drain, remove the lint and whatever else is in there, rinse and replace. Monthly from now on.
- Run an empty cycle at the hottest setting with a machine cleaner. A dedicated cleaner is designed to reach the pump, valve, hoses and tub, which is where a surface wipe cannot go.
- Wipe the seal and the drum dry, and leave the door open. That last step is the one that stops it returning.
Never vinegar and bleach together
Both appear in advice for this job, sometimes in the same article a few paragraphs apart, and combining them produces chlorine gas. Use one or the other, in separate cycles, and rinse between.
Vinegar is the gentler option and it dissolves mineral and detergent residue. Bleach is more effective against established mould and it is harder on rubber seals over time, which is worth knowing before you make it a monthly habit.
Why this is more common than it used to be
Two changes did it, and neither was a mistake. Wash temperatures came down, which is better for fabrics and energy use and considerably better for bacteria. And high-efficiency machines use far less water, so residue that once got flushed away now stays.
The practical consequences are small and specific. Use less detergent than you think, since excess is what feeds the film and modern detergents are concentrated. Run one hot cycle a month even if everything else is cold. And leave the door ajar, which costs nothing and does more than any product.
And skip the fabric softener
Softener is a waxy film by design, and inside a machine that film is exactly what biofilm needs to attach to. It also builds up in the dispenser, which is one of the three places the problem lives. If you want softer laundry, wool dryer balls do the job mechanically and leave nothing behind in the machine.
The one designed to reach where a cloth cannot
12 tablets, one a month, a year’s supply. Works in front loaders, top loaders and HE machines.
Wiping the seal and the drawer deals with what you can see. The pump, the valve, the hoses and the underside of the tub are where the rest of it lives, and a tablet designed to release through the cycle is the practical way to reach them.
This is the brand recommended by Whirlpool, Maytag and Amana, which matters mainly because those manufacturers also handle the warranty claims when a machine develops problems. It is EPA Safer Choice certified and septic safe, which is worth checking if you are on a septic system since not all cleaners are.
One practical detail from the maker: one tablet once a month rather than the twice-monthly routine some cleaners require, which halves the maintenance you have to remember. Run it on the hottest cycle with the drum empty.
Worth it or skip: Worth it if the standpipe test pointed at the machine, and worth it monthly thereafter as prevention, since this problem returns unless something changes. Skip it entirely if the smell is sewage from a dry trap, where a gallon of water fixes what no cleaner will.
Three more, by your water and your machine
A powder with a low temperature bleach activator, if you have hard water. Five month supply. This one is worth understanding rather than just buying. It uses oxygen bleach combined with TAED, which is an activator that lets oxygen bleach work at lower temperatures, and the maker claims it boosts the cleaning action by over twenty percent and works in hard water where other cleaners struggle. That matters here specifically, because low wash temperatures are a large part of why machines smell in the first place. The maker also argues powder acts faster than a tablet, which is a direct disagreement with the tablet brands. See the powder cleaner →
A five pack, if you want to see whether it works first. Five months. Same tablets as the year supply in a smaller box, which is the sensible buy for a first attempt when you are not yet sure the machine is the problem rather than the plumbing. Time release, safe for all makes and models including HE, EPA Safer Choice certified and septic safe. If it fixes the smell, switch to the annual pack, since the monthly habit is what keeps it away. See the five pack →
The washer and dishwasher bundle, since the dishwasher has the same problem. 12 tablets, six months of each. A dishwasher is the other appliance in the house that sits damp with food residue in it, and limescale and mineral deposits build up in its pump, filter, spray arms and hoses exactly as they do in a washing machine. If one of them smells, the other is usually not far behind, and buying together is cheaper than separately. See the bundle →
If the whole room smells rather than the machine, the sources are wider than the washer and the diagnosis is different. I go through it in laundry room smells musty, find the source first.
Cleaned it and it still smells? 2 taps
The quiz above is for finding the source. This one is for after an attempt, and the second question usually explains why it did not take.
People also ask about washer smells
Why does my washer smell like rotten eggs?
Rotten eggs is hydrogen sulfide, and it reaches you by one of three routes. Bacteria inside the machine produce it as a metabolic byproduct, sewer gas carries it up the drain, or your water supply contains it, which is common on well water. But before investigating any of those, rule out a natural gas leak: utilities add an odorant to natural gas so leaks can be detected, and that odorant smells sulfurous. If there are gas appliances near the laundry room, leave the house and call the gas company first. Everything else can wait an hour.
Why does my washing machine smell like sewage?
Usually a dry P-trap, and frequently not the washer’s own trap. Every drain has a U-bend holding standing water that seals the pipe against sewer gas, and when a drain goes unused for a few weeks that water evaporates. The washer drains into a standpipe, so the floor drain in the same room sits unused and dries out on its own. Pour a gallon of water down every drain in the room, floor drains included, and repeat every couple of weeks. If the smell survives that, the possibilities are a partial blockage where lint and soap have caught, or a clogged vent pipe, and both want a plumber.
How do I know if the smell is the machine or the drain?
Pull the drain hose out of the standpipe and smell the pipe itself. If the standpipe smells, the problem is the plumbing and cleaning the washing machine will achieve nothing. If the standpipe is fine, the source is inside the machine. Two further clues narrow it down: a smell that appears only during the drain cycle points at biofilm, because moving water disturbs the film and releases the odour, and water from another tap smelling the same points at the supply rather than the appliance.
Why does my washing machine smell when it is new?
Because the conditions changed rather than the machines. Wash temperatures came down and high-efficiency machines use far less water, so residue that once got flushed away and bacteria that once got killed now stay. Front loaders are hit hardest, since a horizontal drum needs a watertight door seal and that seal is a rubber fold that holds water, lint and detergent between loads. Three habits prevent almost all of it: use less detergent than you think, run one hot cycle a month even if everything else is cold, and leave the door ajar between loads.
Washer smell FAQ
Where is the drain pump filter?
Behind a small hatch at the bottom front of most front loaders, sometimes behind a hinged panel. Put a towel and a shallow tray underneath before you unscrew the cap, because there will be water. Clean it monthly, which is standard manufacturer advice and something almost nobody does, largely because most people do not know the filter exists.
Vinegar or bleach?
One or the other, never both, and never in consecutive cycles without rinsing between, since together they produce chlorine gas. Vinegar is gentler and dissolves mineral and detergent residue. Bleach is more effective against established mould and harder on rubber seals over time, so it is a treatment rather than a monthly routine.
Does fabric softener cause this?
It contributes. Softener works by depositing a waxy film, and inside a machine that film is exactly what biofilm attaches to. It also builds up in the dispenser drawer, which is one of the three places the problem lives. Wool dryer balls soften mechanically and leave nothing behind, which is the straightforward swap.
How much detergent should I use?
Less than the cap suggests, and considerably less in a high-efficiency machine. Modern detergents are concentrated and HE machines use little water, so excess does not rinse away: it stays as residue and feeds the film. If your laundry comes out feeling slightly slippery or the drawer is crusted, you are using too much.
What if I have well water?
Then the rotten egg smell may be the supply rather than the appliance, since well water frequently contains hydrogen sulfide. Test it by running water from a different source and smelling that too. If it smells, no washer cleaner will fix it and the answer is filtration. This is worth checking before spending money on cleaners.
When do I call somebody?
For a sulfurous smell with gas appliances nearby, immediately and from outside the house. For a burning or hot plastic smell, stop using the machine and get it looked at, since that is a mechanical or electrical fault rather than anything to clean. And for a sewage smell that survives refilling the traps, since a partial blockage or a clogged vent pipe needs tools and expertise.
The washer smell cheat sheet
Rule this out first
Rotten eggs plus gas appliances in the room means leave and call the gas company. Natural gas has no smell; utilities add a sulfurous odorant so leaks can be detected. A washer smell is at the machine. A gas smell is in the air.
The two minute test
Pull the drain hose out of the standpipe and smell the pipe.
Pipe smells → plumbing. Cleaning the machine will do nothing.
Pipe fine → the machine. Seal, drawer, drum, pump filter.
Four smells, four places
Musty → mould in the seal, drum and drawer.
Sewage → dry trap, usually the floor drain the washer never uses. A gallon of water.
Rotten eggs → bacteria, well water, or gas.
Burning → mechanical fault. Stop using it.
Why it keeps coming back
Less detergent than the cap says. No fabric softener, which is a film by design.
One hot cycle a month, even if everything else is cold. Clean the pump filter monthly.
Leave the door ajar. Costs nothing, does more than any product.
Free printable
The Cozy Home Starter Checklist
A hot cycle a month and a gallon of water down the floor drain are exactly the sort of jobs that never happen without a list. This printable walks you through a home room by room, catching the small habits that prevent the unpleasant surprises.
Keep reading
- Laundry Room Smells Musty? Find the Source First
If the whole room smells rather than the machine, the sources are wider and the diagnosis is different. - Stiff Towels Have Three Causes. Vinegar Only Fixes One
The same detergent and softener residue, showing up in the laundry rather than the machine. - Two of These Three Causes Are Fixable. One Is Not
Where softener buildup shows on fabric, and the one cause of hardness that no wash reverses. - Where the Water Sits Tells You Which Problem You Have
Drying laundry indoors releases almost five pints a load, which has to go somewhere in the house. - Small Laundry Room Decor: How to Make the Least Loved Room Cozy Without Renovating
Once it stops smelling, the room itself repays a small amount of attention.
Name it, test it, then clean it
Most advice on this treats a smelly washing machine as one problem with one routine, which is why so many people scrub a drum for an evening and find nothing has changed. There are four smells and they come from four different places, and one of them is not the washing machine at all.
So name it first. Musty is mould in the seal, the drum and the drawer. Sewage is a dry drain trap, and usually the floor drain that the washer never uses because it drains into a standpipe instead. Burning is a mechanical fault and means stop using the machine. And rotten eggs is hydrogen sulfide, which can be bacteria, can be well water, and can be a natural gas leak, because the odorant utilities add to gas smells of sulfur.
That last one is why this article opens where it does. If your laundry room has gas appliances and the smell is sulfurous, leave and call the utility. Being wrong about that costs you a phone call. Being wrong the other way costs more.
Then do the two minute test before anything else: pull the drain hose out of the standpipe and smell the pipe. It tells you whether you are cleaning an appliance or refilling a trap, and those are not the same evening.
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