Blog
Why Does My Washing Machine Smell?
Why Does My Washing Machine Smell?
Causes, Prevention, and How to Tackle It
Why Does My Washing Machine Smell?
A musty, damp, or drain-like smell coming from your washing machine is one of the most common complaints we hear. The smell often transfers to freshly washed clothes, which defeats the whole point of washing them. The good news is that in most cases it’s preventable, and with the right routine you can clear it and keep it away.
Almost every smelly washing machine comes down to one underlying problem: biofilm. This is a sticky layer of detergent residue, fabric softener, body oils, and organic matter that builds up inside the machine and provides a home for bacteria and mould. Once it takes hold, it produces that unmistakable musty smell.
The root cause: Modern washing habits – cooler washes, liquid detergents, and plenty of fabric softener – create the perfect conditions for biofilm. Low temperatures don’t break down residue or kill bacteria, so it slowly accumulates in the drum, drawer, seal, and pipes.
The honest truth: There’s no guaranteed cure for a smelly machine. Most modern drums are sealed or welded shut, so the biofilm inside the outer tub simply can’t be reached – not even by an engineer. Repeated long hot washes can sometimes improve things, but if the smell is severe and ingrained, it can be a case of managing it rather than fully curing it. This guide is about giving your machine the best possible chance.
What Causes a Smelly Washing Machine?
1. Biofilm Buildup (The Main Cause)
Biofilm is the sticky residue that lines the inside of the drum, pipes, and hidden parts of the machine. It’s made up of detergent, softener, grease, and organic matter from your clothes. Bacteria and mould thrive in it, and that’s what produces the smell. Biofilm is behind the vast majority of smelly machines.
2. Mould in the Detergent Drawer
The detergent drawer and its housing are a common hiding place for mould and residue. Fabric softener in particular leaves a thick sludge that builds up in the drawer and the compartment behind it. This is often overlooked because people don’t think to clean it.
3. Mouldy Door Seal
The rubber door seal traps water and residue in its folds, making it a prime spot for black mould. A mouldy seal is both a cause of smells and a sign that biofilm has taken hold elsewhere in the machine. Read our guide on mouldy washing machine door seals for more detail on this.
4. Blocked or Dirty Filter
The filter traps coins, lint, and debris that could otherwise block the pump. Over time it collects trapped water, fluff, and gunk that starts to smell. Many people have never cleaned their filter and don’t know it exists. A neglected filter is a common source of drain-like odours.
5. Standing Water and Poor Drainage
If water isn’t draining away fully – due to a partial blockage or an issue with the waste pipe – it can sit stagnant in the machine and start to smell. A drain-like or sewage smell in particular can point to a drainage problem rather than biofilm.
Washing Habits That Make It Worse
Certain everyday habits speed up biofilm buildup and make smells much more likely:
Always washing cool
Cooler washes save energy, but if your machine never sees a hot cycle, detergent residue and biofilm never get broken down. An occasional hot wash keeps things in check.
Too much detergent and softener
Over-dosing leaves residue that doesn’t rinse away. Fabric softener is especially bad – it leaves a sludgy film that feeds bacteria. Using less actually leaves your machine cleaner.
Leaving wet washing in the drum
Leaving a finished load sitting in the machine for hours lets damp clothes and the drum turn musty quickly. Get washing out and dried as soon as the cycle finishes.
Keeping the door and drawer shut
Closing the door straight after a wash traps moisture inside. This is worse for machines installed in an enclosed area, where the cupboard door stays shut and the seal never dries out.
Machines in Enclosed Spaces Smell Faster
Integrated and enclosed machines are more prone to smells as the seal never dries out
Integrated washing machines – and freestanding machines installed in an enclosed area – are particularly prone to smells. Because the cupboard door is usually kept closed, the washing machine door stays shut too, trapping moisture inside. The seal and drum never get the chance to dry out between washes, so biofilm and mould develop faster. Leaving both the machine door and cupboard door open after a wash makes a real difference.
How to Tackle the Smell
Tackling a smelly machine means going after the biofilm in all the areas you can actually reach. This won’t always fully cure a badly affected machine, but it gives it the best possible chance and improves things in most cases:
1. Run hot maintenance washes
Run an empty cycle at the highest temperature (usually 90°C), or use the machine’s drum clean program if it has one. This helps break down residue and kill bacteria. A dedicated washing machine cleaner or a large dose of soda crystals helps shift stubborn biofilm. For an ingrained smell, several long hot washes in a row often work better than a single one – it can take repeated cycles to make a difference.
2. Clean the detergent drawer
Remove the drawer completely and scrub away any mould and softener sludge. Clean inside the housing too, as residue builds up in the roof of the compartment where you can’t see it. A used toothbrush works well for the corners.
3. Clean the filter
Locate the filter (usually behind a small flap at the bottom front), place a shallow tray and towels down to catch water, and unscrew it. Clear out any debris and trapped water, and rinse it clean. Check your manual if you’re not sure where it is.
4. Wipe the door seal
Pull back the folds of the rubber seal and wipe out any water, hair, and residue. If the seal is only lightly marked this will help, but if it’s badly mouldy and ingrained it will likely need replacing rather than cleaning.
If the smell won’t shift: A persistent drain-like or sewage smell that survives a deep clean often points to a drainage or waste pipe issue, which can be checked. If it’s a musty smell coming from deep within the machine, though, it may be biofilm inside the sealed outer tub that simply can’t be reached – in which case repeated hot washes to manage it are usually the only option.
How to Keep It Smelling Fresh
Once you’ve cleared the smell, a few simple habits will keep it from coming back:
Run a hot wash regularly
A hot wash or drum clean cycle every week or two keeps biofilm from building up. This is the single most effective way to keep a machine fresh.
Leave the door and drawer open
Let air circulate after each wash so the drum, seal, and drawer dry out. For enclosed machines, leave the cupboard door open too.
Go easy on detergent and softener
Use the correct dose – usually less than you think. Cutting back on fabric softener in particular reduces the sludge that feeds bacteria.
Clean the filter occasionally
Check and clean the filter every few months to clear out trapped debris and water before it starts to smell.
The golden rule: Heat, air, and less detergent. Run regular hot cycles, let the machine dry out between washes, and go easy on the detergent and softener. Do these and your machine should stay fresh.
Washing Machine Problems in Bath or Wiltshire?
If the smell won’t shift or you suspect a drainage fault, we can help. We’re washing machine repair specialists serving Bath, Chippenham, Trowbridge, Keynsham, Melksham, Radstock and surrounding areas of Somerset and Wiltshire. Over 30 years experience with all major brands. Which? Trusted Traders.
Email: glen@bathwashco.com
Related Washing Machine Advice
• Mouldy Washing Machine Door Seals – Causes, prevention, and replacement
• Washing Machine Not Draining – Drainage faults that cause smells
• All Washing Machine Repairs – Our main repair services
Which? Trusted Trader