Distilled water

In general, non-purified water could cause or interfere with chemical reactions as well as leave mineral deposits after boiling away.

For example, ions commonly found in tap water would drastically reduce lifespans of lead–acid batteries used in cars and trucks.

These ions are not acceptable in automotive cooling systems because they corrode internal engine components and deplete typical antifreeze anti-corrosion additives.

Fish and other living things that have evolved to survive in lakes and oceans should be expected to thrive at mineral ranges found in their original habitat.

[6] Controlled impurities as well as equipment reliability are critically important in medical applications where, for example, distilled water is used in continuous positive airway pressure (CPAP) machines to humidify air for breathing.

Until World War II, distilling seawater to produce fresh water was time-consuming and expensive in fuel.

During World War II this equipment became standard on Allied ships and on trailer mounts for armies.

[12] Distilling water with commercial equipment will almost completely remove all dissolved minerals such as calcium, magnesium, sodium, fluoride, potassium, iron, and zinc leaving a TDS of <1PPM, and reduce its electrical conductivity to <2 μS/cm.

Municipal water supplies almost always contain trace components at levels which are regulated to be safe for consumption.

Municipal water supplies often have minerals added or have trace impurities at levels which are regulated to be safe for consumption.

The study found that "drinking water sources available to North Americans may contain high levels of calcium, magnesium, and sodium and may provide clinically important portions of the recommended dietary intake of these minerals".

As noted in the American Journal of Epidemiology, consumption of hard drinking water is negatively correlated with atherosclerotic heart disease.