The type of water you wash your hair with can drastically affect how it looks and feels. Hard water, which is high in minerals, can make hair dry, dull, and harder to manage. Softer, filtered water helps hair stay smoother, shinier, and easier to style.
Hard Water
Hard water is everywhere. It’s estimated that over 85% of US households have some degree of hard water, depending on their local water source:
- Contains high levels of calcium, magnesium, iron, manganese and some other metals
- Alkaline (pH ~8.5), which lifts the cuticle and makes hair rough and dry
- Leaves behind mineral buildup on the scalp and hair shaft
- Can make conditioners less effective
These minerals aren’t inherently harmful (calcium and magnesium are good for you when you drink them!). But when they’re coating your hair and skin during every shower? That’s when problems can arise.
Soft Water
Soft water is water that has low levels of minerals like calcium and magnesium. It feels smoother on your skin and hair, and it helps shampoo and soap lather more easily:
- Lower in minerals but higher in sodium
- Slightly acidic (pH ~6.5), which helps seal the cuticle
- Rinses shampoo and conditioner more thoroughly
- Generally gentler on hair
What Else Is in Your Water?
Municipal tap water may also contain:
- Chlorine (to kill bacteria, but can strip oils and irritate skin)
- Other heavy metals (like lead, copper, arsenic)
- Pesticides, chemical runoff, and old pipe residue
How Hard Water Affects Your Hair
Those calcium and magnesium minerals in hard water don’t just “rinse off.” They cling to your hair shafts, creating a mineral buildup that changes your hair texture for the worse over time.
These contaminants can lead to:
- Dryness and brittleness
- Scalp irritation
- Accelerated fading of color-treated hair
This study found that hair exposed to hard water became rougher, less elastic, and more prone to breakage compared to hair washed with soft water.
The real kicker? This mineral buildup prevents your shampoo from doing its job. That means you’re more likely to deal with stubborn residue that weighs your hair down, kills its shine, and can even contribute to scalp flaking or irritation.
How to Protect Your Hair from Water Damage
- Use slightly acidic pH (between 4.3 and 5.0) shampoos and conditioners to neutralize the alkalinity of hard water
- If you don’t have a whole home water filtration system, install a shower filter, such as Jolie, Eskiin, Rorra, or Vitaclean that removes chlorine and minerals.
- Consider a clarifying treatment 1–2 times per month (if you use hard water) to remove buildup
- Always follow shampoo with a quality conditioner to restore the hair barrier
To see what chemicals are in your water supply, click this Water Report.
(Go to the bottom of the page to search by ZIP code)
Filtered water combined with slightly acidic pH hair products creates a healthier scalp environment, helping to support hair strength, reduce inflammation, and promote resilience.
Water Temperature for Hair Washing
The temperature of your water has a significant impact on the health of your hair and scalp.
Hot Water:
- Strips away natural oils
- Causes dryness, frizz, and cuticle damage
- Can lead to scalp irritation over time
Cold Water:
- Doesn’t effectively dissolve oil or remove buildup
- Can leave behind product residue or scalp debris
Lukewarm Water (Best Option):
- Gently opens the hair cuticle.
- Helps shampoo and conditioner penetrate and cleanse
- Prevents unnecessary dryness or damage
You may also finish with a cool water rinse to help seal the cuticle, reduce frizz, and lock in moisture. This gives your hair a smoother, shinier, and more manageable finish, especially for fine or frizz-prone hair types.
