Distilled water is water that has virtually all of its impurities removed through distillation. Distillation involves boiling the water and re-condensing the steam into a clean container, leaving most contaminants behind.
Purified water can come from any source, including spring water, well water, seawater, or municipal water. This source water is then processed by reverse osmosis or deionization to produce a water that is indistinguishable from distilled water from any other source. Purified water contains no dissolved solids. Purified water may also be unhealthy because minerals and ions are being pulled out of it due to reverse osmosis.
The human body needs ions for the brain to function properly. Many of these ions are attained through water, often under the name electrolytes. Distilled and purified water lack these ions, so prolonged ingestion of distilled or purified water may lead to brain malfunction.
A spring is a point where groundwater flows out of the ground, and is thus where the aquifer surface meets the ground surface.
Dependent upon the constancy of the water source (rainfall or snowmelt that infiltrates the earth), a spring may be ephemeral (intermittent) or perennial (continuous).
Water issuing from an artesian spring rises to a higher elevation than the top of the confined aquifer from which it issues. When water issues from the ground it may form into a pool or flow downhill, in surface streams. Sometimes a spring is termed a seep.
Minerals become dissolved in the water as it moves through the underground rocks. This may give the water flavour and even carbon dioxide bubbles, depending upon the nature of the geology through which it passes. This is why spring water is often bottled and sold as mineral water, although the term is often the subject of deceptive advertising. Springs that contain significant amounts of minerals are sometimes called 'mineral springs'. Springs that contain large amounts of dissolved sodium salts, mostly sodium carbonate, are called 'soda springs'.
Drinking water is water that is intended to be ingested by humans. Water of sufficient quality to serve as drinking water is termed potable water whether it is used as such or not. Although many sources are utilized by humans, some contain disease vectors or pathogens and cause long-term health problems if they do not meet certain water quality guidelines. Water that is not harmful for human beings is sometimes called safe water, water which is not contaminated to the extent of being unhealthy.