How to Clean a Washing Machine and Why It Started Smelling

You pull a load out of the machine, shake out a towel, and there it is — a faint smell of damp, the kind of smell you associate with a cloth left screwed up in the sink overnight. The clothes are clean. They went in clean-ish and came out washed. But they smell wrong, and no amount of extra detergent has ever fixed it. At some point the thought arrives, and it is the correct one: the problem is not the washing. It is the machine.

The appliance that washes everything you own is, for most households, the one appliance that never gets washed itself. That is not a failure of character. Nothing about a washing machine advertises that it needs cleaning — it is full of hot water and detergent several times a week, which sounds like the definition of self-cleaning. It isn’t, and this article is about why, and what to do.

What is that smell, and where does it actually come from?

The smell is not dirt in the ordinary sense. It is biofilm: a soft, slippery layer made of undissolved detergent, fabric softener residue, body oils, skin cells, lint and the bacteria that live comfortably in all of it. Biofilm forms anywhere that stays damp and never gets scrubbed. A washing machine is full of such places.

If you run a finger somewhere hidden inside your machine and it comes away with something grey, tan or greasy on it — not gritty, but slick — that is biofilm. It has a smell of its own, and every load of laundry passes through it.

There are four places it lives, and they are worth naming precisely, because they are the four places you will be cleaning:

• The detergent drawer and the cavity behind it. Detergent and softener sit in the drawer between washes, and the housing the drawer slides into is rinsed only by whatever water passes through. The roof of that cavity is often the worst surface in the whole machine.
• The rubber door seal on a front-loader — the flexible grey boot around the opening. It has folds. Water pools in them. This is where black mould appears, and it is usually where the smell is strongest.
• The outer tub, the sealed plastic shell surrounding the drum you can see. You cannot reach it. Residue coats it, and water never fully drains from it between washes.
• The drain filter, usually behind a small flap at the bottom front. It catches everything the pump would otherwise choke on, it holds standing water permanently, and most people have never opened it.

Why do modern machines smell more than old ones did?

This is the part almost nobody explains, and it reframes the whole problem.

Washing has moved to low temperatures. A great deal of laundry is now done at 30°C or below, often 20°C, with liquid detergent. There are good reasons for that — it is gentler on fabric, colours last longer, and heating water is the expensive part of a wash cycle. Cold washing is, on its own terms, a sensible habit.

But it has a side effect. Low-temperature water does not kill the bacteria living in the machine, and it does not fully dissolve detergent and softener residue. Powders and liquids are formulated to work cold, and they do clean your clothes — but what doesn’t rinse away stays behind on the surfaces we just listed. Warm, wet, and fed a fresh supply of organic material several times a week, the machine slowly cultivates exactly the conditions biofilm wants.

So the honest framing is not “my machine is dirty and I’ve been careless.” It is: the way most of us wash now guarantees this will happen eventually. Every household that washes cold is on the same schedule. Some just get there sooner.

Is fabric softener making it worse?

Yes, and it is worth saying plainly.

Fabric softener works by depositing a thin waxy coating onto fibres — that is the entire mechanism, and it is why towels feel plush and lose absorbency at the same time. The coating is not selective. It goes onto the drum, the dispenser, the hoses and the seal exactly as readily as it goes onto a T-shirt, and at low wash temperatures it does not rinse off. That film then traps lint and skin cells and gives bacteria something to hold onto and eat.

You do not have to give up softener. But if your machine smells and you use it in every load, that is the single easiest variable to change, and reducing the dose alone often helps.

What should you have ready before you start?

Nothing exotic. Most of this is hot water and patience.

• An old toothbrush and a narrow bottle brush
• A few microfibre cloths and some old towels
• A shallow tray or roasting tin — this matters, see the filter section
• Washing-up liquid and very hot water in a bowl
• A mild acid: white vinegar or citric acid powder, for limescale and residue
• Bicarbonate of soda, for odour
• Rubber gloves

Before you begin, find your machine’s manual. Machines differ more than you would expect — some have removable seals, some absolutely do not; some manufacturers specify what you may and may not put in the drum, and using the wrong thing can affect your warranty. Two minutes with the manual, or the model number typed into a search box, is time well spent.

Safety, and this one is not a formality: never mix bleach with any acid. Bleach combined with vinegar, citric acid, or acidic limescale removers releases chlorine gas, which is genuinely dangerous in an enclosed space like a utility room or a bathroom. Never combine them in the drum, never combine them in a bucket, and never use one straight after the other without rinsing thoroughly in between. Pick one approach — acid or bleach — and stick to it for the whole job. If you have already used bleach somewhere in the machine, run a full rinse cycle before any acid goes near it.

How do you clean the detergent drawer properly?

Start here, because it is the easiest win and it is nearly always filthy.

1. Take the drawer out completely. Many people do not realise this is possible. Pull it out until it stops, then look for a small coloured tab, button or lever — usually in the middle of the softener compartment. Press or lift it and the drawer slides all the way free. If yours resists, check the manual rather than forcing it.
2. Soak it. Put it in a sink or bowl of very hot water with washing-up liquid for fifteen or twenty minutes. Softener residue softens dramatically with heat and comes away with a brush instead of scrubbing.
3. Take out the siphon. The little plastic insert in the softener section usually lifts out. Underneath it is a reservoir that has probably never been touched. Clean both parts.
4. Now do the cavity. This is the important half. Shine a torch into the empty housing and look at the roof of it — the underside of the surface the drawer slides beneath. There is often a thick, dark, slimy deposit there, and it is usually worse than the drawer itself. Scrub it with a toothbrush and hot soapy water, working upward. A bottle brush reaches further back.
5. Dry it and put it back before you move on, so it is not sitting wet.

How do you clean the door seal on a front-loader?

Wear gloves and have the bin nearby.

Pull the rubber boot gently back towards you, fold by fold, all the way around. It has more folds than it appears to — usually an outer lip, an inner channel, and a groove at the bottom where everything collects. In that groove you will typically find water, lint, a hair grip, and black specks along the rubber.

Wipe every surface with a cloth wrung out in hot soapy water, going right around the circle. For stubborn residue, a cloth dampened with diluted vinegar left resting against the rubber for ten minutes softens it. Then dry the whole seal thoroughly with a towel — including the underside of the bottom fold, which is the bit that stays wet forever.

A note about black mould on the seal: it can often be reduced, but it cannot always be removed. Once the staining has penetrated the rubber, scrubbing harder does nothing except damage the seal, which is a watertight component you very much want intact. Clean it, dry it, keep it dry going forward, and accept some discolouration. If the rubber is perished, split, or the mould is under the surface across large areas, that is a replacement part and an engineer’s job, not a cleaning job.

Do not use anything abrasive on the seal, and do not leave bleach sitting on rubber for long periods — it degrades it.

What actually cleans the drum?

An empty machine run at its highest available temperature. That is genuinely most of the work.

Heat is doing something you cannot replicate with products at 30°C: it melts the greasy residue coating the drum and the outer tub, kills the bacterial population, and flushes the lot out through the drain. Many machines have a dedicated drum-clean or maintenance cycle, which is essentially a long, very hot wash with extra agitation. If yours has one, use it. If not, use the hottest cotton cycle you have — 90°C if it’s offered, 60°C at minimum.

Run it completely empty. No clothes, not even towels. Fabric absorbs the water and residue you are trying to flush out.

What to put in it, choosing one:

• White vinegar or citric acid — roughly a couple of hundred millilitres of vinegar, or a few tablespoons of citric acid powder, in the drum or the main detergent compartment. Good for limescale and detergent residue.
• Bicarbonate of soda — a few tablespoons in the drum. Better for odour than for scale.
• A small dose of ordinary detergent — surprisingly effective, since detergent is a degreaser, and the residue is largely grease. Use less than a normal load, or you add to the problem.

Do not combine acid and bleach, as above. And check your manual before putting vinegar through the machine regularly — a handful of manufacturers advise against it because of the seals, and a strong acid used weekly is not the same as used occasionally.

When the cycle finishes, wipe out the drum, leave the door open, and let it dry.

Where is the drain filter, and why does it matter so much?

If you do one thing on this list, do this one. The drain filter is the single most neglected part of a washing machine and it is very often the true source of a bad smell.

It sits behind a small hatch or removable panel at the bottom front of the machine, usually on one corner. Some are hidden behind a clip-off plinth. You may need a coin or a flat screwdriver to lever the flap open. It exists to catch everything that would otherwise wreck the drain pump: coins, buttons, hair grips, shredded tissue, hair, lint, and the occasional small sock.

Because it sits at the low point of the system, it also holds standing water permanently. Water plus trapped organic debris plus warmth is the ideal biofilm environment, and it is sealed away where nobody looks.

Water will come out. Plan for it.

1. Turn the machine off at the socket.
2. Lay old towels across the floor in front of it and press a shallow tray or roasting tin up against the base. There is often more water than you expect — a litre or more — and a washing-up bowl is too tall to fit under the opening.
3. Open the hatch. Many machines have a short drain hose tucked beside the filter — pull it out, remove its cap, and let it empty into the tray first. This is much less messy than unscrewing the filter cold.
4. Unscrew the filter itself, usually anticlockwise. Expect a further gush.
5. Pull it out and look at it. Rinse it under a hot tap, brush the mesh clean, and clear any debris from inside the housing with your fingers — carefully, since there may be something sharp in there.
6. Reach into the empty housing and check the impeller if you can see it: a small propeller-like fan. It should turn freely. If it is jammed by an object, remove the object.
7. Screw the filter back in firmly and straight, replace the hose cap, and close the hatch. A loose or cross-threaded filter leaks, so make sure it seats properly.
8. Run a short rinse cycle and check underneath for drips before you push the machine back.

Nobody is born knowing this hatch exists. If yours has never been opened and the machine is several years old, expect the contents to be unpleasant — that is normal, not a verdict on your housekeeping.

What about the outside, the hoses and behind the machine?

Quicker, but worth finishing the job.

Wipe the door glass, the rim, and the control panel with a damp cloth — the panel with a barely damp one, since you do not want water getting into buttons. Clean the underside of the door, which people forget, and the top of the machine where detergent drips dry into a crust.

Pull the machine forward if you safely can and look behind it. Check that the drain hose is not kinked or crushed against the wall, and that dust and lint have not built up on the back. If there is a puddle, damp plaster, or a green crust on the inlet valve where it meets the tap, that is a leak, and a leak is a plumbing job.

Are cleaning tablets worth buying?

Honest answer: they work, they are convenient, and they are largely doing what a hot maintenance wash with a cheap acid does.

Purpose-made machine cleaners are typically a combination of acid, a bleaching or oxygen-releasing agent and surfactants, pressed into a tablet or bottled as a liquid. They dissolve limescale, break down grease, and deodorise. There is nothing fake about them. If you like the simplicity of dropping one thing in the drum four times a year and never thinking about it, that is a completely reasonable way to spend a small amount of money.

What is worth knowing is what they cannot do. A tablet cannot reach into the folds of your door seal, it cannot scrub the roof of the detergent cavity, and it cannot empty your drain filter. Those three jobs are where most of the smell lives, and they are hand jobs regardless of what you put in the drum. A machine that gets a tablet every month and has never had its filter opened will still smell.

So: buy them if you prefer them. You are not obliged to, and if the packaging implies that a smelly machine means you skipped a product, that is marketing rather than plumbing.

Does any of this change for a top-loader?

The principles are identical; the geography differs.

Top-loaders generally have no rubber door boot, which removes the worst single problem area. In its place, pay attention to the underside of the lid, the rim of the tub opening, and — on machines with a central agitator — the agitator column itself, which can be a hollow tube full of residue. Some agitators unbolt for cleaning; check the manual, since forcing one is an expensive mistake.

Top-loaders also often use much more water, which means residue is diluted and flushed more effectively, so they smell less as a rule. But they hold water in the tub bottom, and any dispenser cups for bleach or softener need the same soaking treatment as a front-loader’s drawer.

The maintenance-wash principle is the same: empty, hottest cycle, one cleaning agent. Filter arrangements vary — many top-loaders have a lint filter rather than a front drain filter, so find yours in the manual.

How do you stop it coming back?

This is the actual answer, and it is where most advice stops one step short. Cleaning fixes today. Habits fix next year.

• Leave the door ajar between washes, and pull the drawer out an inch too. Biofilm needs damp. A machine that dries out between loads cannot build it up at anything like the same rate. This single habit does more than any product. If you have small children or pets, a door that is only slightly open — or open only while you are around — is a sensible compromise.
• Take the washing out promptly. A finished load sitting warm and wet for six hours is a bacterial incubator, and that is where the “wet dog” smell in clean clothes usually starts.
• Run a hot maintenance wash periodically, even though you wash cold day to day. Roughly monthly is plenty for most households; every couple of months is fine for light users. This is the counterweight to cold washing, not a contradiction of it.
• Use less detergent than feels right. Overdosing is the most common cause of residue, and the dose on the packet assumes a full load in a hard-water area with heavy soiling. A half-full load of lightly worn clothes in soft water needs considerably less. More detergent does not mean cleaner clothes — past a point it just means more residue in your machine and in the fabric.
• Reconsider fabric softener, at least in every load. Try alternate loads, or a half dose, and see whether you notice.
• Wipe the seal dry when you empty the machine. It takes ten seconds and it is the highest-value ten seconds in this entire article.

What if you live in a hard-water area?

Hard water adds a second problem on top of biofilm: limescale, which builds up on the heating element and on internal surfaces, and which detergent residue then binds to. Scale makes the machine less efficient at heating water, which in turn makes low-temperature washing even less effective at clearing residue — the two problems reinforce each other.

The fix is the same mild acid you have already got: an occasional hot empty wash with white vinegar or citric acid dissolves scale before it thickens. Scale builds fastest in hard-water areas, so if your kettle furs up quickly, your machine is quietly doing the same thing.

What do the common problems actually mean?

Clothes come out smelling

Almost always biofilm in the drum, tub or filter, plus wet laundry left sitting. Do the full clean above, prioritising the filter and the seal, then fix the habits. If the smell returns within a fortnight, the filter or the drain hose is the likely culprit rather than the drum.

Clothes come out marked

Grey or greasy streaks usually mean residue transferring from the machine, which the drawer clean and a hot maintenance wash both address. Overdosed detergent that never dissolved is the other common cause — try a smaller dose and a rinse cycle. If the marks are specific and localised rather than general greying, they may be ordinary stains that survived the wash, which is a different problem covered in how to remove stains from clothes. Rust-coloured marks appearing in the same spot every time suggest a damaged drum, and that needs an engineer.

Water is not draining

First, check the filter and the drain hose for a kink or blockage — a jammed filter is the most common cause and is fixable in ten minutes. If the filter is clear and the machine still will not empty, or you hear the pump straining, stop. That is a pump or electrical fault and it needs a professional.

It only smells on certain cycles

Very informative, actually. A smell that appears only on short or cold cycles usually means residue is present but only being disturbed and not flushed — the water is too cool to clear it. A smell that appears only on hot cycles often means the biofilm is being heated and released, which sounds worse but is a sign the hot wash is working. Run two or three maintenance washes rather than one and it typically fades.

How often should you realistically do all this?

Not as often as a thorough article implies. A workable rhythm:

• Every wash: wipe the seal, leave the door and drawer ajar.
• Monthly: hot empty maintenance wash. Quick rinse of the detergent drawer.
• Every three months: the drain filter. Full drawer and cavity scrub. Thorough seal clean.
• Once a year: pull the machine out, check hoses and the space behind it.

If you have a large household, wash heavily soiled work clothes, or live with hard water, shift each of those up a notch. If it is one or two people washing lightly, you can relax them.

When should you stop and call someone?

This article is about cleaning. It is not about repair, and there is a clear line between the two.

Stop, unplug the machine, and call a qualified engineer if you find any of the following:

• Standing water that will not drain after you have cleared the filter and checked the hose
• Any leak — from underneath, from the door, or at the tap connection
• A burning smell, a smell of hot plastic, or scorch marks anywhere
• Anything electrical: tripping the circuit, a damaged cable, a scorched plug, or the machine cutting out mid-cycle
• Loud grinding or knocking during the spin, which suggests bearings or a foreign object past the filter
• A door that will not unlock with water inside

Do not open the casing, do not work on a machine that is plugged in, and do not attempt anything on the water supply beyond turning the tap off. Cleaning is yours. Electrics and plumbing are not.

Energy Star and the EPA WaterSense programme both publish what machines actually consume, which matters if you are weighing a hot maintenance wash against its running cost.

The EPA Safer Choice list is worth checking before putting any cleaning product through a machine.

Frequently asked questions

Can I use bleach to clean my washing machine?

You can, and it is effective against mould, but only on its own — never in combination with or immediately after vinegar, citric acid or any acidic limescale product, because the mixture releases chlorine gas. Check your manual first, since some manufacturers advise against bleach because of its effect on rubber seals over time, and run a rinse cycle afterwards before doing anything else.

Will vinegar damage my washing machine?

Occasional use in a maintenance wash is widely done and generally fine. The concern is frequency: acid used weekly over years can degrade rubber seals and hoses. A few times a year is a reasonable ceiling, and citric acid is a gentler option. Your manual is the authority for your specific model.

Why does my machine still smell after a hot wash?

Almost certainly because the smell is not in the drum. The drain filter, the detergent cavity and the folds of the door seal are all sealed off from the wash water, so no cycle reaches them. Do those three by hand and the hot wash will then be doing the job it can actually do.

Do I need to leave the door open all the time?

Ajar is enough — it does not need to swing wide. The goal is airflow so the drum and seal dry out. If an open door is a hazard in your home, leave it open for a few hours after a load and close it once the inside is dry.

Is it worth using cleaning tablets every month?

Monthly is more often than most machines need, and it will not compensate for an uncleaned filter or seal. If you like them, every two to three months alongside the hand cleaning is plenty. A hot empty wash with a small dose of ordinary detergent achieves much of the same thing.

Should I stop washing at low temperatures?

No — cold washing is genuinely better for fabric and cheaper to run, and there is no reason to abandon it. The point is simply that it needs a counterweight: one hot empty cycle a month keeps the machine honest while your everyday washing stays cold.