Hard water is water that contains dissolved minerals such as calcium, magnesium, iron, silica, etc. The minerals in the water bond to the hair strand and creates a hard coating on the hair which makes it difficult for it to absorb moisture. The more damaged and open your hair cuticles are, the more the minerals in the hard water will cling to your hair. One way of knowing if the water in your home is hard is by looking at your taps and showerheads. If there is a hard white-ish build up on your taps and showerheads. There is a likely chance that the water in your area is hard.