Less than 1 percent of all freshwater usage is for drinking water purposes. The other 99 percent is consumed by domestic sanitary functions, irrigation, etc., but the majority goes to commercial and industrial applications. Next to air, water is the most important element to the subsistence of human life. When we do think about water we usually visualize a crystal clear mountain stream flowing from a beautiful waterfall. Technically, it is not pure.
Pure water exists only in a laboratory.
It is difficult to produce and even harder to maintain. Two basic sources of water must be understood before you can proceed further. This includes oceans, lakes, rivers, snow and ice. This is water held under the surface of the earth in different geological formations. The water enters the formation via percolation of water from precipitation and direct seepage from surface water sources.