Your skin is an Organ. In fact it is largest organ in your body and It is mostly made up of water. Without water your skin can not function properly. Your skin does not get enough water, not only will it become dry, tight and flaky but it will also become more prone to aging.
As water is important factor for the Skin, same way the purity of water should consider. Pure water helps to maintain moisture which increases your elasticity of skin.
If you have sensitive skin you should know the pH of your water. Hardness of water is also responsible for the sensitive skin. Hard water contain minerals such as calcium and magnesium which react with fatty acids in soap to form chemicals that coagulate and do not dissolve in water. These chemicals result in dry sensitive skin. If you have sensitive skin you might notice you have more skin irritation when you wash with hard water. Hard water is especially problematic for people who have skin conditions such as eczema and dermatitis. In extreme cases hard water even lead to Hair loss.
Hard water also affect your teeth. Minerals containing the hard water are responsible for damage of your teeth. So you should test your water for finding out their Hardness, amount of minerals present in them. And then It will better for your Skin, Hair and Teeth.