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Hydrologist, water engineer, water sommelier (yup, that’s a thing) — you don’t have to be any of these to know that not all H2O quality is the same. It's most noticeable when you go on vacation, say from New York to Martha’s Vineyard or Virginia to Las Vegas, and your hair feels totally different after washing it. Water can be harder in some places around the country, and the level of hardness can make one city better for a good hair day than another.
Maybe you’ve never given much thought to the water coming out of your showerhead beyond if it’s too hot or cold. But if you’ve noticed that your hair feels dry and brittle, your roots get greasy quickly, or that your hair color needs to be touched up more frequently than you (and your wallet) would like, perhaps it’s because you’ve been showering with hard water. And the chances that you’re impacted are high: A whopping 85% of the United States has hard water.
In 2024, brands have started to zero in on how hard water is affecting our hair and scalp. Is this just a new marketing angle or are the effects something we should seriously worry about? We spoke to dermatologists, hair colorists, a trichologist, a cosmetic chemist, and a hydrologist to clear things up.
- Rachel Bodt is a colorist and the owner of Homecoming Salon in New York City.
- Dendy Engelman, MD, is a board-certified dermatologist in New York City.
- J. Matthew Davis, PhD, is an associate professor at University of New Hampshire’s department of earth sciences, and an expert in groundwater hydrology.
- Garren is a hairstylist based in Miami and New York City.
- Valerie George is a Los Angeles-based cosmetic chemist and president of the product and research development lab Simply Formulas.
- Hope Mitchell, MD, is a board-certified dermatologist in Perrysburg, Ohio, and founder of Mitchell Dermatology.
- Uchenna Okereke, MD, is a board-certified dermatologist in Boston.
- Jenna Perry is a colorist and owner of Jenny Perry Hair Studio in New York City.
- Helen Reavey is a hairstylist and certified trichologist in New York City.
- Todd V. Royer, PhD, is an aquatic ecologist specializing in water resources, water quality, and nutrient standards. He is also an adjunct professor with Indiana University’s Biology Department and interim editor in chief at Freshwater Science.
- Iris Rubin, MD, is a board-certified dermatologist in Washington DC.
- What is hard water?
- How to tell if you have hard water
- Is hard water safe?
- How does hard water affect your hair?
- How does hard water affect your scalp?
- How does hard water affect your hair color?
- Does hard water cause hair loss?
- How to reduce the hard water in your shower
- Products to Help Minimize the Damage From Hard Water
- A Final Word on Hard Water
What is hard water?
A quick science lesson: Water hardness is generally determined by the amount of dissolved minerals in your H2O, namely calcium and magnesium. In its pure state, water tends to be “soft.” It becomes hard when it comes into contact with soil, which in the US is often full of calcium and magnesium ions that readily dissolve in the water, explains Todd Royer, PhD, an aquatic ecologist specializing in water resources, water quality, and nutrient standards and an adjunct professor with Indiana University’s Biology Department. That means if you get your water supply from the ground — whether that’s pumping it out of a well or your city gets water out of a river or lake — your water contains some level of calcium and magnesium. The more traces of these dissolved minerals the harder your water. “The reason why some areas have naturally soft water and others have very hard water is simply a function of the mineralogy of the soil and the underlying bedrock,” says Dr. Royer.
It doesn’t stop there. All of our water — hard or soft — also contains small amounts of copper, iron, and either chlorine or chloramine. The latter two are added to water at safe levels determined by the Environmental Protection Agency to kill parasites, bacteria, and viruses that could be harmful. While these are great for protecting your guts against nasty stuff like salmonella, the reality is, that none of these elements are great for your hair or your scalp.
How to tell if you have hard water
I moved from New York City to London five years ago and went from worrying about mold in my Queens apartment to figuring out how to combat limescale and soap scum in my London flat — two telltale signs your H2O is on the harder end of the spectrum. And unless you are that 15% of the US population with soft water, you also might find that you also need more soap to get things really clean.
This is because when soap comes into contact with calcium and magnesium, it reacts and forms a precipitate known as soap scum, which makes it hard to rinse off, explains J. Matthew Davis, PhD, an associate professor at University of New Hampshire’s department of earth sciences, and an expert in groundwater hydrology. The term “hard water” comes from the fact that it makes it “hard” to clean things with soap, says Dr. Royer.
Soap scum can accumulate in your bathtub, your shower curtain, your sink, and your clothes, leaving them feeling stiff or looking slightly dingy. When heated, such as in a hot water heater, hard water can precipitate into mineral deposits and clog pipes, adds Dr. Davis, which explains the limescale in my shower and electric kettle. It’s a more serious issue in industrial settings where they can’t have that scale forming in pipes.
In terms of your skin and hair products, hard water reduces their ability to lather and can make complete rinsing difficult, says Iris Rubin, MD, a board-certified dermatologist based in Washington DC. (Soft water, in comparison, creates more bubbles and lathers more easily.) If you have very hard water, your average shampoo might not be enough to cleanse the mineral buildup or the film left on your scalp and strands (more on why that's a problem in a minute).
You might also be able to tell just by how your hair feels and looks. “Consistently showering in hard water tends to leave the hair feeling dry and dull, whereas soft water tends to leave it shinier,” says Helen Reavey, a hairstylist and certified trichologist in New York City. From personal experience, after my move across the Atlantic, I noticed a lot less volume and texture in my hair and my roots got greasier, faster.
Is hard water safe?
While hard water might be bothersome, an important point to make before diving any deeper is that hard water is not dangerous to drink or wash with. “From a human health standpoint, there are no verified or documented human health effects of hard water, so it’s not something that water treatment plants spend a lot of money on,” explains Dr. Royer. “It’s really just about convenience and aesthetics.”
How does hard water affect your hair?
While hard water can adversely affect all hair types, those with fine, fragile, and colored-treated hair may notice the biggest impact, says Garren, a hairstylist based in both Miami and New York City. According to the pros, the main issue with hard water comes down to the buildup of mineral deposits on and in your hair, and the leftover product that can’t be fully washed out, both of which leave behind a residue on the hair shaft.
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Firstly, this residue makes it difficult for moisturizing shampoos and conditioners to penetrate and properly cleanse and hydrate the hair, says Dendy Engleman, MD, a board-certified dermatologist in New York City. Secondly, it can weigh down the hair and make it look dull. Add that to the fact that hard water can strip the natural oils from your hair, and you end up with dry, rough, and brittle hair, says Dr. Rubin. This lasting damage is the biggest concern. “The rough texture caused by hard water can make hair more susceptible to breakage, as it becomes less flexible and resilient,” says Hope Mitchell, MD, a board-certified dermatologist in Perrysburg, Ohio.
It also means you might notice more frizz — not just because your hair is drier, but because the salt in the water causes the hair cuticle to become rough and raised. “The hard water takes the cuticle, pushes it open, and then lays it back down in a weird, jagged way,” adds Garren. Because the cuticle is no longer lying flat, your hair looks dull, tangles more easily, and becomes trickier to style. “Products can also no longer properly adhere to the hair, causing your styles to lack hold and definition,” says Reavey.
How does hard water affect your scalp?
When you frequently suds up with hard water, minerals can also build up on your scalp. “This can compromise scalp health and lead to redness and itchiness, particularly if you are predisposed to eczema or psoriasis,” says Dr. Engelman. “It can also disrupt and weaken the normal skin barrier function and potentially exacerbate inflammatory skin conditions like acne, eczema, and dermatitis.”
How does hard water affect your hair color?
Hard water has the most noticeable effect on hair color. In addition to accelerating color fading, the mineral deposits distort hair dye, causing it to turn orange, yellow, or even green, explains Rachel Bodt, hair colorist and owner of Homecoming Salon in New York City.
During peak travel seasons, this is especially common. “I typically see it a lot after summer break and my blonde clients return to the salon,” says New York City-based hair colorist and salon owner, Jenna Perry. “They've got a lot of buildup on their hair. Their color isn’t as vibrant and it can look a little brassy. That’s when you know they were spending time in a place with hard water.” The dulling isn’t just limited to blondes. Brunettes can get darker or go brassy due to mineral buildup, says Bodt, while the lack of vibrancy is especially obvious on redheads, says Perry.
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Fading and color shifting can be annoying and expensive issues to fix, but mineral buildup becomes more problematic when it comes into contact with bleach. “Copper and iron buildup can be especially worrisome because they love to be in the hair,” says cosmetic chemist Valerie George. "They continue to oxidize the hair over time, which can cause a lot of damage, especially if you get your hair colored and bleached.”
In severe cases, heavy metals in the hair react with bleach, a situation that highlights the importance of seeing an experienced colorist. Hydrogen peroxide, which is used in hair lightener and hair color to lighten hair and develop color, is easily catalyzed by metals like copper and iron, explains George. “When these metals are present in the hair, the hydrogen peroxide decomposes and generates a significant amount of heat.” When there is a ton of copper and iron in the hair, that heat can be so intense that it leads to burns or causes the hair to start smoking, damaging the hair structure and leading to breakage, dryness, and split ends.
If you’ve never worried about your hair going up in smoke in the salon chair, now’s not the time to start. A trained and licensed colorist knows how to prevent this from happening, while advancements in hair-color and -care technology mean the chances of a negative reaction are slim. Perry treats every blonde that walks into her salon to the Olaplex Broad-Spectrum Chelating Treatment, while Bodt relies on the K18 Peptide Prep Pro Chelating Hair Complex for many of her clients who have hard water. Both professional treatments contain high levels of tetrasodium glutamate diacetate, a chelating agent which binds to metals and minerals to help remove these impurities. It removes build-up not only on the surface of each hair strand but also in the cortex, which is located in the center of each hair fiber and forms the main bulk and pigment of your hair. Perry calls the Olaplex treatment “hairdresser insurance.” “Sometimes, we do this treatment and that’s all [the client] needs — they don’t even need [new] highlights,” she says, noting how shiny and vibrant the treatment leaves the hair.
Does hard water cause hair loss?
One of the most frequent questions about hard water: Does it cause hair loss? The simple answer is no. “Overtime, prolonged hard water exposure can negatively impact the texture, quality, and health of the hair, but it is not a direct cause of hair loss,” says Dr. Engelman. “However, dry and brittle hair is more prone to breakage and hair loss so over time a combination of factors can lead to hair loss.”
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Oftentimes, hair breakage can be mistaken for hair loss. Acquired trichorrhexis nodosa (ATN) is a disorder characterized by easy breakability of the hair shaft resulting from repeated trauma — like overstyling and overbleaching — or hair that is very dry and brittle. “When I'm looking at a patient's scalp through the dermoscope, if I'm seeing the right number of hair follicles but it's not matching what I'm seeing at their ends, that means they are dealing with breakage, not hair loss,” explains Uchenne Okereke, MD, a board-certified dermatologist in New York City.
It’s important to note however, that many factors can play a role in hair loss so if you’re concerned about your hair thinning or excessive shedding, consult a dermatologist who can determine the exact causes and the correct treatment plan.
How to reduce the hard water in your shower
If your water is hard and it’s severely affecting your pipes and your appliances, you may want to consider installing a water-softening system (consult with a plumber first). A simpler solution, and one that should do the trick if you have hard water, is buying a showerhead filter. They remove a lot of the minerals, heavy metals, and chlorine from your water, they’re a cinch to install, and they’ve never been easier to find.
Hello Klean, which is a UK-based company that specializes in shower-care essentials for hard water, makes two options — a purifying showerhead and a shower filter that attaches underneath your faucet (I swear by the latter). Hot-tool brand T3 offers two versions of its Source Showerhead, which has been around for nearly a decade, while Act + Acre just launched its universal Showerhead Filter, which features 12 different filtration systems, including a proprietary blend of calcium sulfite, charcoal, and KDF-55 (a medium that filters water by a natural chemical reaction).
Dr. Engelman and Perry recommend the Canopy Filtered Showerhead (they both consult for the company), which comes in four different finishes. Then there’s the recently debuted Afina A-01 filter. A majority of these options offer a subscription service that sends you filter replacements every 90 days.
Products to Help Minimize the Damage From Hard Water
To treat hard water buildup on the scalp and the hair, all the experts we spoke to recommend incorporating either a clarifying or chelating shampoo into your hair care routine to help remove the residue and buildup on the hair. Which one you choose depends on how hard your water is.
“Clarifying shampoos and chelating shampoos are not necessarily the same — I think it’s safe to say all chelating shampoos are clarifying shampoos, but not all clarifying shampoos are chelating shampoos,” explains George. Chelating shampoos include chelating ingredients like phytic acid, disodium EDTA, tetrasodium EDTA, sodium gluconate, and citric acid that grab metals out of the hair. Clarifying shampoos also deep clean the hair, but they don’t always contain chelating agents, so it’s important to check the INCI list if you’re looking for a formula that specifically removes heavy metals.
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Because clarifying and chelating shampoos also remove the hair’s natural oils, they’re not for regular use – once a week, or once every two weeks, will suffice. “Be sure to follow with a good conditioner, and also consider a leave-in conditioner if your hair is dry, to restore moisture,” Dr. Rubin adds.
A weekly scalp treatment will also be beneficial for removing hard water buildup, says Dr. Engelman, which will help clarify the skin on your scalp and promote a healthy microbiome. Here are a few expert-recommended products that can help combat the effects of hard water.
When it comes to at-home products, Perry swears by this gentle clarifying formula that combines chelating ingredients like trisodium ethylenediamine disuccinate and citric acid with moisturizing panthenol and Olaplex’s proprietary bond-building molecules. “I love it because it’s sulfate-free, non-stripping, and keeps your hair color shiny and vibrant.”
Bodt recommends this color-safe, deep-cleansing shampoo, which combines the brand’s signature K18Peptide with both clarifying and chelating ingredients, strengthening the hair strands as it breaks down and rinses away oils, product build-up, and mineral deposits.
This chelating shampoo starts as a rich cream and then lathers to a lightweight foam that gently removes metal deposits in the hair, leaving strands looking lustrous and feeling soft and silky.
If you have curly hair, or your hair is especially dry and brittle, Dr. Okereke recommends cleansing your scalp and hair with this apple cider vinegar rinse after you’ve shampooed. “This rinse is great at removing build-up without stripping your hair and scalp of moisture and does so with natural ingredients such as apple cider vinegar,” Developed by board-certified dermatologist, Dr. Camille Howard, the formula is gentle enough for dry, brittle or color-treated hair and it is free of sulfates. A bonus: castor oil and shea butter help add moisture back to your hair. In addition to ACV, the rinse also contains the chelating ingredient, disodium EDTA.
I like this clarifying shampoo because it has both chelating and clarifying ingredients to detox hair and remove mineral deposits,” says Dr. Okereke, who notes this formula is also great for curly hair textures due to its moisturizing properties.
To remove impurities in the hair, Bodt also loves this clarifying treatment. Apple cider vinegar is a classic, natural ingredient that breaks down build-up and adds shine to the hair. Look lower down on the INC list, however, and you’ll spot disodium EDTA and citric acid — both chelators — that latch onto heavy metals in the hair and rinse them away.
Moisturizing and deep-cleaning, this is another one of Dr. Okereke’s top picks. “Great for the hair and scalp, this is a clarifying shampoo with ingredients such as argan and avocado oil to prevent it from stripping hair of moisture.” Chelators tetrasodium EDTA and disodium EDTA sit at the lower end of the INCI list to remove mineral build up.
Garren recommends this lightweight conditioning rinse from his R+Co range to keep your hair shiny and smooth and your color looking bright. Free of sulfates and synthetic fragrance, the treatment uses a combination of kombucha, sodium citrate, and citric acid (the latter of which are chelating ingredients) to draw out minerals like calcium and iron from the hair, preventing tangles and leaving strands feeling silkier and looking shinier.
Infused with probiotic-rich sake water, antioxidants, and plant extracts, “this product is great for balancing the scalp microbiome, removing build up, and promoting healthy hair,” says Dr. Engelman.
Reavey recommends weekly scalp treatments to remove build-up on the scalp, ensuring the microbiome stays balanced and clean. Several drops of the cold-pressed oil that she developed has the added benefit of restoring the scalp’s moisture barrier to relieve dryness and itchiness, too.
A Final Word on Hard Water
In 2024, we are beginning to see more product ranges dedicated specifically to combating the negative effects of hard water. Formulated to remove heavy metals and mineral buildup in the hair, these products contain high amounts of chelating ingredients, says George.
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While the majority of Americans have hard water, if you haven’t noticed it negatively affecting your hair or your skin, then it’s unnecessary to switch up your entire routine. “If your hair is moderately healthy and you don't have super hard water, it’s not going to be an issue,” says George. “ If you have very damaged and bleached hair, you will probably benefit from a [shower] filter and everyone could benefit from a chelating shampoo every now and again.”
If you do have hair and skin issues, it’s also important not to jump to conclusions. Hard water might play a small part, or no part at all. “Maybe you’re not shampooing your hair properly. Or maybe you have dandruff or rosacea,” says Garren. “You need to address these conditions with a doctor before blaming it all on the water. ”
More ways to keep your hair healthy.
- 14 Best Pre-Wash Hair Oils for Softer, Shinier Hair
- Split End Treatments to Add Life Back to Damaged Hair
- Hair Masks That'll Help Soften and Revive Your Texture
Now watch how to remove unwanted calcium build-up on your hair.
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