hard water shampoo guide | Friendly Soap

A Guide To Using Shampoo Bars In Hard Water

The performance of natural shampoo is greatly affected by hard water. We've done a bit of digging and tried to shine some light on the subject. Read on for a look at our guide to using Friendly Soap’s natural shampoo bars in hard water. 

What is hard water?

Water that has high levels of minerals is called hard water. In order for water to be considered "hard", it must contain high levels of calcium and magnesium. These minerals can come from the ground, as well as surface water sources like lakes and rivers. Hard water is not harmful, but it can cause numerous problems. This ranges from corrosion of metal pipes, scale build-up on fixtures and appliances, and reduced soap efficiency.

Why is there a problem with shampoo bars and hard water?

Shampoo bars are a popular alternative to traditional liquid shampoo, but they can be problematic for people who have hard water. When traditional natural soap comes into contact with the minerals in hard water it causes a chemical reaction that changes the sodium salt component in soaps into their calcium and magnesium salt counterparts, thus resulting in an insoluble white-grey residue. This can build up on shampoo bars, making them difficult to use and less effective at cleaning hair. It can also build up on the scalp and hair, making it difficult to rinse out the shampoo and causing the hair to feel greasy and heavy. This is just one of many pros and cons of shampoo bars.

How to use a shampoo bar in hard water

When it comes to hard water, you may be wondering how to use shampoo bars.

To use a shampoo bar in hard water, start by wetting your hair thoroughly. Rub the bar between your hands to create a lather, and then apply the lather to your hair. Massage the lather into your scalp, using circular motions, and then rinse thoroughly. Repeat if necessary.

If the hard water has left a residue that's difficult to wash from hair, an apple cider vinegar or baking soda rinse may help to soften the water chemically.

A Sodium Bicarbonate (baking soda) solution can be used to rid your hair of the mineral build up caused by hard water. While this is perfect for removing the mineral build up, it doesn’t solve the problem of hard water, as you then re-apply the minerals when you rinse your hair from your supply. Apple cider vinegar is a natural way to remove hard water build up from your hair. The acetic acid in the vinegar breaks down the minerals in the water, which causes them to stick to your hair. This can leave your hair feeling heavy and greasy. To avoid this, dilute the apple cider vinegar with water before using it as a hair rinse.

If you are in any doubt or are not really up to such a drastic change in habits, then natural shampoo bars, when used in very hard water areas, are probably not for you.

We know that the problem can be solved with a few alterations to lifestyle, we also fully understand that people often just don’t have the time or patience for it and so feel that it is better, for everyone involved, that we are open and transparent about it from the start.

What shampoo is best for hard water?

If you have hard water, it's important to find a shampoo that is designed to work well with hard water. Shampoo that is designed for hard water will help to prevent build-up on your hair and scalp. Shampoo bars are a great option for people with hard water because they are made with natural ingredients that help clarify and cleanse the scalp and hair, despite being slightly more difficult to use. They also tend to be less drying than traditional shampoos, making them a good choice for people with dry or sensitive scalps. Natural shampoos that contain tea tree oil or other clarifying ingredients can also be effective in hard water environments.

Best shampoo for hard water UK

Our Lavender and Tea Tree Shampoo Bar is made with all-natural ingredients such as lavender essential oil and tea tree oil - both known for their cleansing qualities. This bar is also vegan-friendly, cruelty-free, SLS free and plastic free - making it perfect for those looking to reduce waste while keeping their hair healthy. The bar produces a thick lather which helps coat each strand of hair with nourishing oils, making it the perfect hard water shampoo. This is also one of the best natural shampoo bars there are.

Are you in a hard water area?

We have collected a list of the areas of the UK that are considered to have the hardest water.

hard water area map

01. Ipswich – 423* 11. Reading – 323
02. Colchester – 379 12. Cambridge – 322
03. Luton – 360 13. Dartford – 315
04. Norwich – 359 14. Hull – 313
05. Watford – 358 15. Bath – 312
06. Stevenage – 355 16. Bromley – 311
07. Swindon – 343 17. Milton Keynes – 309
08. Harrow – 335 18. Canterbury – 308
09. Hemel Hempstead – 333 19. Slough – 303
10. St Albans – 323 20. Portsmouth – 296


* Numbers represent calcium carbonate levels ppm or mg/l


Which shampoos should I avoid using in hard water? 

It’s unfortunate but natural shampoo bars don’t always work particularly effectively in hard water. This is because natural shampoo bars are often soap based and don’t contain surfactants to boost their cleansing properties. For example, shampoo bars can be worked into a thick, soapy lather in the same way that non-natural shampoo bars can, though this can be done much less effectively in hard water.

However, natural shampoo bars are much better for both your hair and the environment overall, so we recommend still trying to make the switch work for you.

Why doesn’t natural shampoo work well in hard water? 

Hard water has a high mineral content, which can react with the ingredients in natural shampoo bars and may make it much more difficult to thoroughly rinse the shampoo away. This could lead to shampoo residue being left behind after washing and giving your hair a greasy or oily appearance, even right after cleansing. 

The use of shampoo bars in hard water is also affected by the pH levels of the water. If you do use a natural shampoo bar in hard water, however, you may want to try following it up with an acid rinse. Rinsing with a natural acid, such as apple cider vinegar, may work to break down the residue left behind and leave you with a cleaner result. 

What are the effects of hard water on shampoo bars?

The high mineral content in hard water can cause shampoo bars to become ineffective and can also cause them to leave a residue on hair.

Shampoo bars are made of saponified oils and typically contain no harsh chemicals, sulfates, or other detergents. This makes them a more natural option for those looking to avoid harsh chemicals in their haircare products. However, there is some concern that the high mineral content of hard water may be detrimental to the performance of shampoo bars.

Hard water contains high levels of minerals, such as calcium and magnesium, which can interfere with the lathering and cleansing abilities of shampoo bars. As a result, shampoo bars may not work as well in hard water environments and can leave behind a film on hair.

In areas with hard water, shampoo bars can be difficult to lather and may not rinse cleanly. This can lead to build-up on the scalp and hair, which can cause problems like dandruff, itching, and frizziness.

In addition, hard water can also shorten the life of shampoo bars.

How do I fix the problem?

There are a few ways to fix the problem of hard water and shampoo bars. One is to use a filter to remove the minerals from the water. Another is to use a shampoo that is designed to be used with hard water.

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