Most people who complain that their washing machine “still smells” have not actually failed at cleaning it. They have solved the wrong problem. A washing machine can go wrong in several distinct ways, and each one calls for a different fix, so a household can be diligent, spend money on products, and still end up disappointed simply because the treatment did not match the cause.

This guide walks through what is actually happening inside a modern machine, why energy-saving habits have made the problem more common, and how to build a maintenance routine that solves it properly rather than papering over it.

The Real Cause: It’s Not Dirt, It’s Biofilm

The smell that develops in a washing machine is rarely down to visible dirt. It is caused by biofilm: a thin, living layer of bacteria, fungi, detergent residue and body oils that coats the inside of the drum, the door seal and the pipework. Biofilm forms wherever there is repeated moisture and organic material, and a washing machine’s drum is close to an ideal environment for it.

This is largely a side effect of energy-conscious habits. Washing at 30°C or 40°C is far cheaper and greener than washing at 60°C, but detergent does not fully dissolve at those lower temperatures, and fabric softener leaves behind a sticky film that traps lint and moisture. Bacteria thrive in exactly those conditions. The result is a machine that looks clean on the outside while quietly building up a layer of gunk on the inside, one low-temperature wash at a time.

Limescale is a separate issue again, caused by hard water rather than biofilm, and it needs an entirely different kind of product to shift it. Mixing the two up, treating a smell with a descaler, or treating limescale with an antibacterial cleaner, is the single most common reason people conclude that machine cleaners “don’t work”.

Drum Clean, Tub Clean, Eco Clean: What That Blinking Light Actually Means

Most machines built in the last decade or so include a dedicated maintenance cycle, though every manufacturer names it differently. Samsung calls it Eco Drum Clean, LG calls it Tub Clean, Bosch and Siemens simply call it Drum Clean, and Beko uses DrumClean+. Whatever the label, it is the same idea underneath: a hot, empty cycle, typically running between 60°C and 70°C for 60 to 90 minutes, designed purely to sanitise the machine rather than to wash laundry. This detailed explanation of what the drum clean function does and how each major brand implements it is a useful reference if you are trying to work out what your particular model’s reminder light is asking you to do.

A few points are worth knowing before you press the button. The cycle should always run on an empty drum, adding laundry can damage both the fabric and the machine. Whether you are allowed to add a cleaning product varies by brand: Samsung and Beko generally advise against it, arguing the heat alone is sufficient, while LG actively recommends pairing the cycle with a cleaning tablet. Checking your manual before adding anything is worth the two minutes it takes, since using the wrong product in the wrong cycle can occasionally affect a warranty.

It is also worth being realistic about what this automated cycle cannot do. Heat is very effective at killing bacteria, but it does not reach into the folds of the rubber door seal, does not touch the detergent drawer, and will not clear an established limescale problem on its own. Those need to be dealt with separately and by hand.

Diagnose Before You Buy: Four Different Problems, Four Different Fixes

Before spending money on any product, it helps to work out which problem you actually have. Broadly, machines run into trouble in four ways:

• A musty or “wet dog” smell, with laundry that never quite smells fresh, points to biofilm and calls for a hot shock-treatment cycle at 60°C or above.
• A chalky white residue, a heating element that is struggling, or cycles that run longer than they used to, points to limescale and calls for an acidic descaler.
• Black spots spreading across the rubber door seal are mould, and no cleaning cycle reaches inside those folds on its own; they need to be wiped out by hand before any treatment will hold.
• If nothing is wrong yet, the goal is simply prevention: a monthly hot maintenance wash, and a water softener product if you live somewhere with hard water.

Roughly 60% of UK homes are in a hard or very hard water area, concentrated across London, the South East, East Anglia and parts of the Midlands. If that’s you, descaling deserves equal priority alongside odour control, and doing them in the wrong order (deodorising before descaling) tends to produce the disappointing “it only worked for two weeks” result that a lot of online reviews describe.

A Maintenance Routine That Actually Works

The most effective approach combines the automated cycle with a small amount of hands-on attention, since neither one alone covers everything:

• Run the built-in drum clean or hottest empty cycle roughly monthly, more often if you are in a hard-water area or mostly wash at 30°C.
• Empty the filter every month. A blocked filter produces the same stagnant smell as biofilm, costs nothing to fix, and is the single most commonly overlooked culprit.
• Wipe the door seal by hand every couple of weeks, folding it back to check for the trapped water and grey slime that hide inside the folds.
• Remove and wash the detergent drawer monthly; it sits outside the drum’s water circulation and will not be touched by any automatic cycle.
• Every three to four months, add a proper chemical treatment on top of the routine hot cycle, since heat alone is excellent at killing bacteria but weak against limescale and established residue.

Choosing a Cleaning Product, If You Need One

Not every household needs a dedicated cleaning product, a hot wash and a well-kept filter and seal solve a good proportion of cases for free. Where a product does help is on a machine that has been neglected for a while, or in a hard-water home where limescale needs an acidic treatment that heat alone cannot provide. Products in this category fall into fairly distinct types, powder shock treatments for odour and biofilm, acidic descalers for limescale, and water-softening tablets used with every wash to stop scale forming in the first place, and picking the wrong category for your problem is the most common reason people end up unimpressed. This independently tested comparison of the leading UK washing machine cleaners breaks the options down by exactly that problem-first logic, rather than ranking everything on one blended scale, which is a more useful way to shop than picking whichever bottle is cheapest on the shelf.

Common Mistakes That Undo Good Intentions

• Running the maintenance cycle cool or lukewarm. Temperature does most of the actual work, so the hottest setting available is the right one for this job.
• Leaving the door shut straight after a wash. A sealed, damp drum is an ideal environment for the exact bacteria you are trying to get rid of; leave the door and drawer ajar to dry out.
• Using bleach, or mixing an acidic descaler with a bleach-based product. Acid and bleach together release chlorine gas, and bleach itself degrades rubber seals over time.
• Assuming one treatment will undo years of neglect. A genuinely neglected machine often needs two runs, one to loosen the build-up and a second to flush it away.
• Buying a descaler to fix a smell, or an antibacterial cleaner to fix limescale. These are different chemistries solving different problems, and this mismatch is behind most of the one-star reviews you’ll see for otherwise perfectly good products.

The Bottom Line

A washing machine that smells is not a mystery, and it is not usually a fault with the appliance itself. It is almost always the predictable result of low-temperature washing combined with a maintenance routine that has fallen behind. Running the built-in hot cycle monthly, keeping the filter, seal and drawer clean by hand, and reaching for the right kind of product, descaler or antibacterial treatment, only when the diagnosis calls for it, will keep most machines fresh, efficient and free of the two-monthly complaint calls to an appliance repairer.

Treat it the way you would any other appliance that works hard on your behalf: a few minutes a month is a great deal cheaper than a replacement heating element, and considerably cheaper than a new machine.