Last updated on April 7th, 2017
Causes of grease, slime and black mould inside washing machines
This article looks at the importance of doing a regular maintenance wash using the hottest wash cycle on washing machines. It describes how to get rid of mouldy, musty or bad smells from washing machines. It’s important to understand the causes, so as to protect from the problem in the first place or prevent re-occurrence. You can also get dirty marks on your laundry from a smelly washing machine. laundry can pick up grease and slime from under the door seal if it gets dragged round the rim of the drum.
Various products available online and in supermarkets claim to freshen up washing machines and get rid of bad odours. My personal experience with these products (which are also aimed at dishwashers) is that they do a good job of freshening up a relatively clean washer or dishwasher. I’ve not found them so effective at curing a genuinely smelly machine though. Especially if the problem has been allowed to get really bad. If your appliance is seriously smelly, and coated in black mould or greasy gunge, then it can be very difficult or even impossible to cure. There are some things worth trying though..
Carry out one or more maintenance washesNot many people use hot washes any more. This is partly to blame for the bad smells. Hot water (above 60°) helps to kill bacteria and cut down grease. One of the first things to try is to put the washing machine on a boil wash cycle (90° or 95°). Use detergent – but no laundry. You may need to try this more than once. Badly affected washing machines caked in bacteria and gunge may be beyond help if left too late.
Soda crystals dissolve grease. So you might also want to try to clean the washing machine inside with them. Pour half a packet inside the soap drawer whilst it’s filling with water. Using this method every month or so (or using ordinary detergent if no soda crystals are available) can help prevent smells from your washing machine. Remember if your washing machine is badly affected by grease and slime it may be very difficult to remove it.
Beware of low temperature wash cycles
If you mostly use low temperature washes and (or) liquid detergent this maintenance wash is particularly important. Or if you use washing machine detergent which doesn’t contain bleaching agents such as colour friendly detergent. If this is you then buy some normal detergent that does contain beaching agents to use for your maintenance washes. This will help kill off bacteria and prevent black mould and grease. Tip: Look for something like, "bleaching agents" in the ingredients. Some manufacturers recommend using biological detergent for the maintenance wash. I’m not sure exactly why because biological detergent only really works at low temperatures. Biological enzymes get killed off at high temperatures. It might be worth trying both biological and non biological detergent. The main criteria is – no laundry and very hot wash cycle.
Don’t put chemical cleaning bleach in the washing machine, there are certain types of bleach (eg. oxygen bleach) that are appropriate for laundry.
Get rid of washing machine odours using vinegar
White distilled vinegar has an array of uses. I've had reports back from people that distilled white vinegar does actually work. Try putting half a cup of white (distilled) vinegar inside an empty washing machine on a boil wash cycle. Wait until the washing machine has been filling for several seconds before pouring the vinegar into the soap drawer. This is because the first bit of water going into a washing machine runs into the sump hose and is sealed off.
What causes washing machine smells?
Washing machines now commonly suffer from a build up of a greasy deposit and bacteria. This gunge causes bad smells, rots hoses & door seals and blocks the pressure system causing overfilling or spin failure. An even more serious consequence of this problem is that the aluminium based drum spiders can be corroded by the build up of grease and gunge. That can cause one or more of the drum’s arms to break. This is often fatal to the washing machine.
This problem was virtually unheard of before the 1980s. But when detergents started to become more "environmentally friendly" and then liquid detergents were invented this issue suddenly appeared. It seems that the problem is worse when a combination of factors are involved. Almost everyone suffering the worst cases of this slimy grease uses 40° or 30° washes almost exclusively. If combined with poor quality detergents, not using the recommended quantities, or only using colour-friendly detergents or liquid detergent it allows bacteria to thrive. Over time this can seriously rot a washing machine inside.
Example of the level of gunge that can build up inside a washing machine.
Large deposits of grease, slime and undissolved detergent have built up on the underside of this door seal. It smells. An analogy I like to use is washing greasy pots in a bowl. If you use very hot water and good detergent everything is fine. But if you wash greasy plates in a plastic washing up bowl with the water at 40 degrees you would have a greasy film coating it the bowl when you drain out the water. The plates still come out clean but the bowl is greasy. To break down grease you need higher temperatures. It’s the same with washing machines. The main outer drum is nearly always made of plastic now.
Carefully examine the inside of your door seal for slime and grease to check if your washing machine is being badly affected. Pull the lip back in front of the drum and look underneath. If the door seal and lip of the main drum are covered in grease and limescale you have a problem that needs dealing with.
Smells from the plumbing
Washing machine smells can also be caused by plumbing issues. Check out this article for more details – Smells caused by plumbing faults.
As described above, low temperature washes are part of the smelly washing machine problem. Read this article for advice on Washing at 30 degrees?