Drinking unfiltered water is dangerous because it could contain parasites, chlorine, fluoride, dioxins, contaminants, undesirable chemicals, and other harmful substances. The purest form of water is distilled water. Distilled water is formed by evaporating water and then condensing it. So it contains nothing but water. It is only logical to think that distilled water is healthy but this is not true.
Drinking distilled water on a regular basis can lead to serious illness and even death. Water is the universal absorbant. It its pure form, it's absorbing capacity is greatly increased. Thus it would absorb essential nutrients, minerals, and electrolytes from your body. This would result is blood pressure irregularities and loss of nutrients. Distilled water is also more acidic as it absorbs more carbon dioxide from the air than regular water.
Most soft drinks such as coke and pepsi are made from distilled. Soft drinks are notorious for introducing artificial sweetners to the body, while causing tooth decay and draining significant quantities fo calcium, magnesium and other minerals into the urine. Mineral loss increases the risks of degenerative diseases affecting muscles, bones, and vital organs especially the heart.
So what kind of water should I drink? Slightly alkaline. Alkaline water contains magnesium and calcium. Longevity is related to drinking hard water. Distilled water is the softest water. Hard water contains minerals such as magnesium and calcium.