How to Clean a Washing Machine Naturally (UK)

If your machine has started giving your clean washing a faint whiff of damp, or you have spotted black speckles in the rubber around the door, you have not done anything wrong. It is one of the most common jobs people forget: the machine washes the clothes, but nothing routinely washes the machine. The good news is that the fix is cheap, mostly natural, and once you have done the full clean it takes about fifteen minutes to keep on top of.

This is a practical how-to using things most UK homes already have: bicarbonate of soda (known as baking soda in the US), white vinegar, soda crystals and washing-up liquid. I will also be straight with you about the one bit the internet gets over-excited about, which is pouring vinegar through your machine every week.

Why washing machines get smelly and mouldy

Two everyday habits are behind almost every musty machine. First, we mostly wash cool now: 30°C or 40°C is kinder to clothes and to the energy bill, but cool water does not melt away grease and detergent residue the way a hot wash does. Second, liquid detergent and fabric conditioner both leave a soft, waxy film behind. Fabric conditioner is the worst culprit, because it is designed to coat fibres and does not rinse away cleanly.

That residue settles in the parts of the machine the water never properly flushes: the folds of the rubber door seal, the detergent drawer and the filter. Given warmth and moisture, it becomes a biofilm, a living layer of bacteria and mould clinging to the surfaces. A peer-reviewed review of washing-machine microbiology confirms that at the low temperatures modern machines run at, a stubborn community of microbes can persist on the machine's water-contact surfaces and on fabrics. That biofilm is what you can smell, and the black spots in the door seal are mould feeding on it. Nothing sinister, just biology doing its thing in a warm damp box.

Front-loading machines, which are what most UK homes have, are the more prone to it, because the horizontal rubber door seal forms a natural pocket that holds water after every wash. Top-loaders are less affected but not immune. Either way, the cure is the same: clean the spots the residue collects in, then change the small habits that let it build up in the first place. If you have never cleaned the machine before, the first full clean might take you an hour; after that, keeping on top of it is a fifteen-minute job.

The full natural clean, step by step

You will need a cloth, an old toothbrush, washing-up liquid, bicarbonate of soda, and either white vinegar or soda crystals for the final wash. Put an old towel down by the filter flap, because there will be water.

Clean the whole machine

1. 1

   Wipe the rubber door seal (where the black mould lives)

   This is the single most important step for smells. Peel the rubber gasket back gently with your fingers and wipe right into the folds with a damp cloth. For black mould, use a paste of bicarbonate of soda and a little water, or a suitable proprietary cleaner, and work it into the creases with an old toothbrush. Rinse, then dry it off. Deeply ingrained staining in old rubber may not lift completely, but you will clear the mould itself.

2. 2

   Soak and scrub the detergent drawer

   Pull the drawer right out (there is usually a release catch or button; your manual will show it). Leave it to soak in warm water with a squirt of washing-up liquid, then scrub the gunk and any mould off with the toothbrush, paying attention to the fabric-conditioner section, which clogs the most. Wipe out the empty cavity it sits in too, then dry and refit.

3. 3

   Clear the filter (pump trap) at the bottom

   Behind the little flap at the front bottom of most machines is the filter, which catches lint, hair and stray coins. Lay your towel down, put a shallow bowl underneath, and if there is a small drain hose, uncap it and let the water run out (empty the bowl a few times). Unscrew the filter, pull out the debris, wash it in warm soapy water, wipe the housing and screw it firmly back in. Do not skip this: it traps water and smells if neglected.

4. 4

   Run a hot maintenance wash, empty

   With the drum empty, run a hot cycle at 60°C (or 90°C if your machine has it) to melt out grease and kill off what is left. You can run it plain, or add a cleaning agent: about 250 to 500 ml of white vinegar in the drum to tackle limescale, OR one to two cups of soda crystals in the drum to cut grease and deodorise, OR a proprietary washing-machine cleaner used per its label. Some people put a little bicarbonate of soda in the drawer and vinegar in the drum. Whatever you choose, do not combine vinegar and soda crystals in the same wash: being an acid and an alkali, they cancel each other out.

Vinegar or soda crystals? An honest comparison

Both are staple UK cleaners and both work, but they are not interchangeable, and the popular "run vinegar through it every week" advice deserves a caveat. You can read the full picture in our guide to cleaning with white vinegar and our guide to cleaning with bicarbonate of soda, but here is the short version for machines.

White vinegar is mildly acidic, which makes it good at dissolving limescale and cutting light grease, and it will kill mould on the seal. The honest nuance: appliance experts, including Consumer Reports, warn that regular, prolonged use of vinegar can break down the rubber seals and hoses inside the machine over time. So vinegar is a good occasional treatment, not a weekly routine.

Soda crystals (washing soda) are alkaline and excellent at cutting through the greasy residue that fabric conditioner leaves behind. The nuance here comes from Good Housekeeping UK and the Royal Society of Chemistry: in hard-water areas, soda crystals can react with the minerals in your water to form limescale deposits, which over the long run could build up in the pipework. So they too are best used now and then rather than every single wash.

Put simply: the gentlest backbone routine is a plain hot maintenance wash once a month, with soda crystals when grease is the problem and vinegar occasionally when limescale is. A proprietary washing-machine cleaner is a fine alternative if you would rather not think about it.

How to stop the smell coming back

Cleaning the machine fixes today's problem; a few small habits stop it returning. Leave the door and the detergent drawer ajar between washes so air can circulate and the seal dries out, because standing moisture is what mould needs. Wipe the seal dry after a wash if you remember. Use the right amount of detergent (more is not better, and the excess just becomes residue), and consider switching from liquid to powder, which leaves less gunk behind. Cutting back on fabric conditioner, or replacing it with a splash of white vinegar in the conditioner drawer, makes a real difference too. Finally, run an occasional hot wash: even just washing your towels at 60°C once a week helps keep the machine's insides clean.

If, after all this, you keep getting mould returning not just in the machine but around the room, the machine may not be the root cause. A poorly ventilated utility room or a wider damp problem can keep feeding mould, and that is worth tackling on its own terms, which we cover in our guide to dealing with damp and mould in the home.