Just as groundwater can be polluted, spring water can also be contaminated. It is a good idea to have spring water checked out or to get full reports or summaries of tests from the company selling spring water. Ideally, these are independent lab reports performed yearly. Also, find out if the water is bottled at the source or transported and then treated and bottled. (Water bottled at the source is preferable.) Though spring water can be costly, it is high on the list of drinkable waters.

Martin Fox, in his book Healthy Water for a Longer Life, suggests that three ideal characteristics of drinking water are: (1) total dissolved solids of about 300 ppm. (parts per million), (2) hardness (containing at least 170 mg./l. of calcium carbonate), and (3) an alkaline pH (over 7.0), to reduce leeching of metals from pipes. Spring and well waters may fit into these categories.

Mineral Water
Really, most waters are mineral waters—that is, they contain minerals. In California, the standard for bottled mineral water is more than 500 ppm. of dissolved minerals. Underground bubbly water, called "natural sparkling water," usually contains lots of minerals, as well as carbon dioxide (CO2). Many companies bottling this "mineral" water must inject CO2 back into the water, since it is easily lost between the ground and bottle. Seltzer is any water that is carbonated with carbon dioxide; it is usually filtered tap water. Club soda is essentially the same, though it usually has more minerals added.

All of these types of waters can also be polluted, though any bottled carbonated water would be free of microorganisms, as they cannot live there. Generally though, they should be checked out for mineral levels and chemicals if you consume them in any quantity. I do not recommend, however, large amounts of these carbonated waters. The carbon dioxide can get into the blood and affect the acid-alkaline balance, although the body usually handles this easily through respiration or kidney filtration.

Filtered Water
Filtration, or purification, involves the removal of extraneous matter, be it chemicals, metals, or bacteria, from water. Legally, anything called a "purifier" must remove 99.75 percent of incoming bacteria. Americans are purchasing about two million home filtering systems yearly, and there are a great many models from which to choose. There are several types of filtration systems that can be used, including carbon filters, both granulated and solid, and reverse osmosis. (Distillation will be discussed separately, next.) It is a good idea to educate yourself about water filtration before purchasing a home unit. In the long run, home filters/purifiers are the least expensive and safest way to obtain good drinking water.

Activated Carbon (AC) is the most common type of filter. The carbon, used for centuries as a filtering substance, is "activated" by exposing it to chemicals at high temperatures and steam in the absence of oxygen. That gives the carbon a large surface on which to attach and absorb contaminants. Most carbon filtration units mechanically and biomagnetically (ionically) filter the water and remove the unpleasant appearance, odor, and taste by cleaning it of bacteria, parasites, most viruses, chlorine, and the heavier minerals and particulate matter. However, carbon is best at removing organic chemicals and chlorine, not perfect for all microorganisms and metals. Basically, they will filter out any particles or organisms over 0.04 microns, or whatever the size of the filter pores. The filters can, however, collect bacteria and sediment; as a result, there is some concern that they may breed bacteria and dump them back into the water. Hot water should not be run through carbon filters because it can cause contaminant release. Carbon is excellent at trapping the larger molecules, chemicals, and larger microorganisms; it is not good at removing inorganic minerals including fluoride bound strongly to sodium or calcium, the way it is added to municipal waters. However, solid carbon filtration is believed to be relatively effective (this is still controversial) at removing many of the toxic minerals with higher molecular weights, such as lead or mercury.