Bicarbonate of Soda in the Washing Machine: How to Use It Properly

Many households struggle with hard towels, musty laundry and a washing machine that no longer smells fresh.

The cupboard is packed with specialist detergents, stronger fabric conditioners and laundry fragrances, yet freshly washed clothes can still feel disappointing. An unassuming kitchen powder can make a difference: bicarbonate of soda, more precisely sodium bicarbonate, can make detergent more effective, reduce odours and help care for the machine. The key is using the correct amount, choosing the right wash cycle and understanding a few limitations that many people overlook.

Why bicarbonate of soda makes a difference in the washing machine

Bicarbonate of soda is not a replacement for detergent. It has a different function: it conditions the water and helps the surfactants in detergent do their job.

“Bicarbonate of soda boosts detergent: fewer chemicals, better results and fresher laundry.”

In practical terms, bicarbonate of soda offers three main benefits:

• More effective dirt removal: Its mildly alkaline action alters the pH of the wash water. This can make many stains and body oils easier to lift away. Detergent then works more efficiently, so laundry can come out clean with the same dose or even a slightly reduced amount of detergent.
• Softer fabrics: Towels, bed linen and T-shirts feel less stiff after washing. Bicarbonate of soda can have a slight effect on water hardness and helps reduce deposits on fibres. The result is fewer towel-like planks.
• Odour neutralisation: Rather than masking unpleasant smells with fragrance, bicarbonate of soda can bind them in many cases. Annoying issues such as sweat, stale laundry-basket smells and the slightly musty scent of damp towels can therefore be reduced considerably.

One persistent misconception is that bicarbonate of soda is the ideal descaler. This is only partly true. It does very little against limescale that has already hardened inside the machine. Acidic products such as vinegar or citric acid are needed for that. Bicarbonate of soda can only help limit new deposits to some extent and reduce odours.

How to dose bicarbonate of soda correctly for laundry

The biggest mistake when using bicarbonate of soda is assuming that more is better. Too much can leave residue in the fibres or make the machine feel greasy. A few tablespoons are entirely sufficient.

Standard washes: everyday clothing, bed linen and towels

For a load of around 5 kg of laundry, use the following:

• Add 1 heaped tablespoon of bicarbonate of soda (approximately 20–25 g) to the wash.
• Select a cycle between 30 and 60°C.
• Continue using your usual detergent, but reduce the amount slightly if the laundry is not heavily soiled.

If you have a 7 kg or 8 kg machine and fill it well, you can increase the amount to 2 tablespoons. Using more does not provide a noticeable benefit, but it does raise the risk of alkaline residue irritating the skin.

Strong-smelling laundry and sportswear

Performance tops, sports bras and training trousers can quickly develop persistent unpleasant odours. This is where bicarbonate of soda can be especially useful:

• Put 1 tablespoon of bicarbonate of soda with the detergent for the main wash.
• Add 1 further tablespoon to the fabric-conditioner compartment so it is released during the final rinse.

This gives laundry extra odour control without drowning it in perfume.

Where to put bicarbonate of soda: drum, detergent drawer or fabric-conditioner compartment?

Different methods are useful depending on what you want to achieve:

• Directly in the drum: Best when odours and stubborn dirt are the main concern. The bicarbonate of soda comes into direct contact with the fabrics.
• In the detergent drawer: A good option for longer or Eco programmes. The powder dissolves gradually and evenly in the wash water.
• In the fabric-conditioner compartment instead of fabric conditioner: Suitable for people with sensitive skin or for baby clothes. Laundry stays pleasantly soft and neutral, without added fragrance.

“People prone to skin irritation can often reduce their use of fabric conditioner and strongly perfumed products by using bicarbonate of soda.”

A bicarbonate of soda treatment for the washing machine

It is not only laundry that can benefit from bicarbonate of soda; the machine can too, particularly if it smells musty or is used mainly for low-temperature washes.

A regular care routine for your washing machine

• Put 100 to 150 g of bicarbonate of soda directly into the empty drum.
• Run a long cycle at a high temperature: at least 60°C, or preferably 90°C if your appliance allows it.
• Once the cycle has finished, leave the door slightly ajar so the drum and seal can dry thoroughly.

You can wipe the detergent drawer and rubber seal with a mixture of warm water and bicarbonate of soda. This removes dirt residue and odours, but it is not a substitute for a powerful descaler if thick limescale deposits are already present.

Bicarbonate of soda and vinegar: a dream team, if kept separate

Many household hacks recommend putting bicarbonate of soda and vinegar into the washing machine together to make everything gleam. From a chemical perspective, that is not especially useful.

Bicarbonate of soda is alkaline, whereas vinegar is acidic. When they meet directly, they may fizz impressively, but they also largely neutralise one another. What remains is a type of salt solution that neither cleans particularly well nor removes limescale effectively.

Using them one after the other makes more sense:

This allows bicarbonate of soda to tackle dirt and odours, while vinegar or citric acid works on fresh limescale and makes towels noticeably softer.

When bicarbonate of soda is not a good idea

Although bicarbonate of soda is helpful for standard laundry, some materials are sensitive to it.

• Wool: This animal fibre can swell in alkaline solutions and gradually lose its structure over time. It is better to stick with dedicated wool detergents.
• Silk: One of the most delicate fibres, silk can lose its sheen and become weaker when exposed to bicarbonate of soda.
• Highly technical sportswear: Treatments that provide breathability or water repellency may suffer over time. When in doubt, check the care label and use only a mild dose.

For very sensitive skin, bicarbonate of soda can also be beneficial because it may reduce the need for fabric conditioner and fragrance. However, anyone prone to dryness or itching should begin with small amounts, allow laundry to rinse thoroughly and add an extra rinse cycle if needed.

How bicarbonate of soda can change your laundry routine over time

People who use bicarbonate of soda consistently usually notice a clear difference after a few weeks: detergent lasts longer, the fragrance is less overpowering and the washing machine smells much more neutral. This is particularly worthwhile in homes with poor bathroom ventilation or in areas with high humidity.

For example, in a three-person household doing two to three loads each week, one or two small packs of bicarbonate of soda per month will usually be enough to support everyday washing, keep sportswear odour-free and give the machine an occasional cleaning cycle. This costs considerably less than buying an additional specialist cleaner from the supermarket and noticeably reduces the number of heavily perfumed products in the home.

If you have been battling stubborn towel odours for a long time, start with bicarbonate of soda in the main wash and citric-acid solution in the fabric-conditioner compartment. Only if there is no improvement at all after several washes is it worth looking at other possible causes: an overloaded drum, wash temperatures that are too low or a detergent that does not suit the water hardness.