Curly Hair And Hard Water: A Detailed Visual Guide
Understanding how hard water affects curly hair and practical solutions for managing mineral buildup, from clarifying treatments to water filtration options.
This post was originally published in 2018, but I've updated it for 2025.
If you're following a curly hair routine and experiencing persistent buildup or lackluster curls despite using the right products, hard water might be the culprit. This is especially common if your curls look great when you travel but struggle at home.
What is Hard Water?
Hard water contains high levels of dissolved minerals, particularly calcium carbonate and magnesium sulfate.
Some signs of hard water include:
- White residue on faucets, shower heads, or kettles
- Soap scum that's difficult to clean
- Spots on dishes after washing
- Reduced soap lather
Most of the United States has moderate to hard water. You can check your area's water hardness through your local water utility's annual report or use inexpensive test strips for a quick assessment.
Soft water is the opposite of hard water, and contains low or no minerals. Distilled water for example has no minerals.
Living in Chicago, hard water has been my curly hair's worst enemy. I look back at pictures of myself when I lived in areas with soft water and envy how easy my hair was to take care of. But regular hard water treatments have helped my hair a lot.
Visual Hard Water Infographic
Complete guide to hard water and curly hair
How Hard Water Affects Curly Hair
Hard water can:
- Create a film of mineral buildup on hair that blocks moisture
- Combine with fatty acids in products to form stubborn residue (hard water buildup)
- Deposit inside the hair (especially high porosity hair), causing oxidative damage, as well as swelling it and making it appear dull[22]
- Abrade the hair, making it thinner [23]
- Cause color fading
- Reduce product effectiveness, especially shampoos
- Lead to itchy scalp buildup
- Make shampoos less effective
- Increase breakage and decrease elasticity [24]
However, some people with finer straighter hair find their hair looks better with hard water, because it adds some body to it.
Ingredients that remove hard water buildup
The process of removing hard water buildup is sometimes referred to as chelation and involves a chelating ingredient binding with the mineral ions so they can be easily rinsed out [25].
Most of these ingredients are acids, which have a low pH. Hair naturally has a low pH (3.67) and pHs as low as 3 are likely safe and effective [21]. That said, the pH of these chemicals undiluted can be much lower! So don't use them on their own unless you know what you're doing.
Citric Acid
Based on my own research, I believe the most useful ingredient for removing hard water buildup is citric acid, because it is common and well-studied.
Lots of people use vinegar (acetic acid) and other acids, but research has shown citric acid is uniquely effective at binding with mineral deposits [26]:
The findings highlight that CA [Citric Acid], which contains three carboxylic acid groups and a hydroxyl group, is particularly effective in forming soluble calcium salts. This property makes it useful for cosmetic applications, especially in hair treatments.
Another huge bonus is that citric acid might actually improve the integrity of hair. There is a reason acids like citric acid are used in "bond building" products [27]. The acids increase crosslinking of keratin proteins, which make up the hair [25]:
Alpha-hydroxy acids, such as citric acid, enable reconstitution of the saline bonds between the ammonium and carboxylate functions of the protein chains of the hair fiber, particularly in damaged hair, via an ion exchange mechanism. This phenomenon induces an increase in the cross-linkage of proteins and hence reinforcement of the hair (59).
Having tried all the ingredients listed in this post, I have had the most success with citric acid.
Vinegar
Lots of people use this for removing hard water buildup but I never had much luck with it and there is not much research behind it. A potential problem is that many people use apple cider vinegar which is manufactured for culinary usage and can vary quite a lot chemically.
Amla (Phyllanthus emblica)
Amla, which is Indian Gooseberry, is usually sold as a powder. It's often used as a hair mask and may have some chelating properties, but as a natural product, it is quite variable.
I have tried amla and it works OK, but not as well as citric acid has for me.
Vitamin C/ Ascorbic Acid
A hairdresser of mine used to recommend using Vitamin C powder to remove hard water deposits. It seems less well studied.
EDTA
EDTA is ethylenediaminetetraacetic acid. There are numerous versions of EDTA such as disodium EDTA and tetrasodium EDTA. this cosmetic chemist on Reddit said these are usually used in very small concentrations to balance the pH of a product/act as a preservative and I'm skeptical they do much for hard water buildup.
Glycolic Acid
I have tried this since I buy it from The Ordinary for scalp treatment. It works great for that but I haven't had much success with it for hard water buildup.
Other chelating agents
There are too many potential chelating agents to list in one post but here are some other common ones:
- Sodium Phytate/phytic Acid: Phytic acid is a naturally occurring acid and sodium phytate is the sodium salt of phytic acid.
- Sodium Gluconate/gluconic acid: Gluconic acid is another naturally occurring acid and gluconic acid is its sodium salt.
Questionable ingredients: clay and activated charcoal
I've seen clay (kaolin and bentonite) and activated charcoal in various hair detox products marketed as both useful for general AND hard water buildup. Clay and charcoal might work for other types of buildup but I'm not sure they can do much about hard water buildup. Also clay is mineral rich so it might ADD minerals to your hair.
Ineffective ingredients for removing hard water buildup
Sulfates
Sulfates are great at removing other types of grime, but not very good at removing hard water buildup. In fact a lot of the chelating ingredients listed above are added to shampoo not to chelate your hair, but to make sure detergents like sulfates can work effectively [28].
Ingredients that make hard water buildup worse
Oils, butters, and other fatty ingredients
Fatty acids in oils, butters, and conditioners can react with minerals in hard water to form deposits on hair.[26]
Soap
Did you know that soap isn't the same as the cleansers usually used in shampoo? And there is a good reason for that. Soap is created by the reaction between fatty acids and alkali. When mixed with hard water, these fatty acids can react with the minerals in hard water to form what's known as soap scum. Needless to say, you don't want it in your hair.
We have a whole article about soap and why you should avoid it.
Magnesium sulfate
Magnesium sulfate is one of the minerals that can be in hard water, so I would not recommend adding more of it to your hair. Magnesium sulfate is commonly called "epsom salt" and I sometimes see it in "texturizing" or "sea salt" hair sprays.
Also this isn't a sulfate detergent (the kind people worry about for "sulfate free" products).
Do Sulfates Mix with Hard Water to Form Buildup?
There is an idea going around on Tik-tok and YouTube (like this video by Dr. Dray) that sulfates mix with hard water to form buildup. It's based on this paper The Effect of Water Hardness on Surfactant Deposition after Washing and Subsequent Skin Irritation in Atopic Dermatitis Patients and Healthy Control Subjects that showed that skin washed with sodium lauryl sulfate in hard water had a potentially irritating buildup of sodium lauryl sulfate[28]. But let's look at the title more carefully, it's not about the effect of sulfates, it's about the effect of surfactants. Sulfates are just one type of surfactant. Sulfate-free shampoos have other surfactants, but they can still have the same problem.
But any shampoo you buy at the store, sulfate-free or not, will have chelating ingredients that prevent this process from happening such as[29]
- EDTA (mentioned above)
- An amphoteric surfactant like cocamidopropyl betaine
- An non-ionic surfactants like decyl glucoside or coco glucoside
Basically this is a known problem and any commercial formulator has accounted for it. You only have to worry about this if you are making your own shampoo or buying from indie brands that may not have a professional formulator.
That said, there are certain surfactants that are known to perform better in hard water including:
- Sodium C14-16 olefin sulfonate
- Cocamidopropyl hydroxysultaine
- Disodium laureth sulfosuccinate
- Decyl glucoside
- Sodium cocoamphoacetate
- Sodium cocoyl glutamate
- Sodium lauroamphoacetate
- Sodium cocoyl isethionate (SCI)
- Sodium lauryl sulfoacetate (SLSa)
- Sodium laureth sulfate (SLeS)
- Ammonium laureth sulfate (ALeS)
A few sulfates are ON this list, as they perform well in hard water! Not all sulfates are the same.
Treatments for hard water buildup
My favorite: Acidic clarifying rinses
What you are looking for here is a packet with an acidic active ingredient.
My favorite is Ancient Sunrise Rain Wash, which has only three ingredients: Citric Acid, Ascorbic Acid, Xanthan Gum. I've used it for years and it makes my hair shiny and soft.
A simple and effective hard water treatment with just three ingredients
Another option is Malibu C Curl Partner Wellness Remedy, though I haven't tried it myself. It has a couple of chelating ingredients: ascorbic acid, sodium gluconate, disodium EDTA, citric acid
A chelating treatment with multiple active ingredients
Make sure you follow the directions on the package- most say not to use too often.
You can also DIY but I recommend having some expertise in working with cosmetics and testing pH. Citric acid is very cheap and many grocery stores carry it.
Hair Masks
Hair masks usually have chelating ingredients in a deep conditioning formula that you leave on your hair for 5-30 minutes.
A deep conditioning mask with chelating properties
Chelating shampoos/clarifying shampoos
Chelating shampoos usually have a couple of chelating ingredients. However, I don't think they are very effective for the following reasons
- Shampoos don't stay on your hair very long
- Shampoos get diluted with water in the shower
- The chelating ingredients are used in very small amounts
I never had any success with the chelating shampoos I tried. But they are easy and quick to use, and some people say they work for them.
If you're look for a curl-friendly chelating shampoo, look for a product that is balanced with conditioning ingredients such as Curlsmith's Curl Reset Detox Shampoo which is formulated specifically to remove mineral buildup.
A chelating shampoo balanced with conditioning ingredients
May or may not work: Shower filters
I've also tried my share of shower filters and they haven't helped at all. It's no surprise that Wirecutter found they didn't work.
The most promising one seems to be the Jolie which did third-party testing, though they wouldn't respond to Wirecutter when asked for details.
If you're rich you can do a whole-house water softening system and have your water regularly tested.
Promising but difficult: Distilled water washing
Distilled water washing is when you wash your hair only with distilled water, which is soft water (no minerals). I admit I'm impressed with some of the results at Reddit's Distilled Water Hair community. But not impressed enough to lug around jugs of distilled water and use it to wash my hair.
Hard water buildup prevention tips
It's hard to prevent hard water buildup if you're washing with hard water, but there are a few things you can do to lessen it
- Use lightweight products low in fatty ingredients like butters and oils
- Avoid putting soap on your hair. Soap is not the same as detergents in shampoo!
- Potentially using lower pH hair products
If you're not sure what products to use, try our porosity quiz to get personalized recommendations.
