This page covers two questions: what hard water leaves on hair, and whether it makes hair break. It does not cover scalp or medical questions. A dermatologist is the right person for those.
What hard water leaves on hair
Hard water carries calcium and magnesium. When you wash with it, some of those minerals stay behind.
- A study of hair strands soaked in hard water or distilled water on alternate days for 30 days found more calcium and magnesium on the hard-water strands and a rougher surface under an electron microscope.
- A study of 20 volunteers who washed their hair in hard or soft water for three weeks found more magnesium on hair washed in hard water. Calcium was not significantly different.
- Lab work on hair structure found calcium deposits, bound with oils from the scalp, forming between the layers of the hair's outer surface.
The effect is on the surface and between layers of the hair. It is a film and a buildup. It is not the same thing as damage.
Hair that has been colored or bleached takes up more of these minerals than untreated hair. In one lab study, the condition of the hair mattered more than how hard the water was.
Minerals can also change how hair feels. One lab study found that calcium and magnesium stiffen hair fibers. That can show up as hair that feels stiffer or less smooth.
Does hard water make hair break?
The studies disagree.
Two studies found weaker hair. Hair strands from 76 men were soaked over three months, half in the hardest district water in one region and half in deionized water. The hard-water strands broke at about 6.6 percent lower force. A second study from the same lab, with 70 men, found the same pattern: strands soaked in hard water needed less force to break than untreated strands or strands soaked in deionized water.
Two studies found no difference. Hair strands from 15 volunteers were soaked on alternate days for 30 days, half in water at about 212 ppm hardness and half in distilled water. Strength and elasticity did not differ. A separate study of 20 volunteers who washed their hair in water at 287 to 533 ppm hardness, compared with softer water, found no significant structural difference under the microscope.
What to take from that:
- The studies that found weaker hair did not state the water's hardness in their abstracts. The two that found no difference did.
- All of them are small, with 15 to 76 volunteers. The ones that report a length ran from three weeks to three months.
- So the honest answer is that hard water leaves mineral buildup on hair, and whether it makes hair break is not settled.
What no study has shown
We found no human trial showing that treating the water changes how hair looks or whether it breaks. We do not promise that a Nuvia system will change your hair.
Hair care matters too. One study found that hair with oil or conditioner on it picked up less calcium from the water than hair without.
What a Nuvia specialist can do is test your water at the tap, show you the hardness, and let you decide whether the scale on your glasses, shower door and fixtures is worth treating.
Find your own number
- See what your water agency reports for your city on the hard water by city page.
- Ask for a free in-home water analysis to measure the water at your own tap.
Sources
- Srinivasan et al., Int J Trichology (hair strands in hard water or distilled water for 30 days; strength and elasticity)
- Srinivasan and Rangachari, Int J Dermatol (calcium and magnesium deposits on hair in hard water; electron microscope)
- Luqman et al., J Pak Med Assoc (hair strand strength after three months in hard water)
- Luqman et al., Int J Trichology (hair strand strength, untreated vs deionized vs hard water)
- Alahmmed et al., Indian J Dermatol Venereol Leprol (electron microscope study of hair washed in hard and soft water)
- Evans, Marsh and Wickett, J Cosmet Sci (calcium and magnesium uptake by hair; authors from Procter & Gamble)
- Evans, Marsh and Wickett, Int J Cosmet Sci (how calcium and magnesium change hair fiber stiffness and combing; authors from Procter & Gamble)
- Marsh et al., ACS Appl Bio Mater (calcium deposits between cuticle layers; authors from Procter & Gamble)
- Somasundaram and Kunjiappan, J Microsc Ultrastruct (calcium pickup on hair and the water used; oil and conditioner)
Questions people ask
Does hard water damage hair?
It leaves a mineral film, and that part is well supported. Breakage is less settled. Two studies from one lab found hair strands soaked in hard water broke at lower force, while two other studies found no difference in strength or in structure.
Will a water system make my hair softer or stronger?
We found no study that shows it. A water system changes the water. How your hair looks and behaves also depends on color treatment, products and how you care for it, so we do not promise a change.
Does colored or bleached hair pick up more minerals?
Lab work says so. In one study, calcium and magnesium uptake depended mainly on the condition of the hair, with colored and bleached hair taking up more, and hair took up notable amounts even after repeated soft water exposure.
How hard is the water at my house?
Your water agency publishes a figure for your city, and a tap test measures your own. See the hard water by city page, or ask for a free in-home water analysis.
Book your free water analysis today.
A Nuvia specialist tests your water at your tap and shows you the numbers.