Drinking water quality is critically important to good health. Ideally, drinking water should be wholesome, physically attractive, free from all harmful organisms and have a chemical content which will promote the health of the consumer.

• The finite amount of water on the planet participates in a recycling scheme that provides for its reuse. This recycling of water is termed the "Hydrologic Cycle".
  
  
• Energy from the sun causes the evaporation of water from the seas, lakes, rivers and streams. Other sources of water vapor include plant and animal life and combustion.
  
  
• The evaporated water may condense in clouds as the temperature drops in the upper atmosphere. Winds may transport the water in the clouds over great distances before releasing it in the form of rain, sleet, or snow which falls to the ground.
  
  
• As the water condenses and falls through the atmosphere, it adsorbs any gases which may be rising from the environment below. This is the principal cause of acid rain and acid snow.
  
  
• Upon reaching the earth, the water either percolates through the soil to the water table or finds its way to a body of water.

Since water, to some degree, can dissolve every naturally occurring substance on earth, it becomes contaminated with the substances that it contacts ... both in the air and the ground.

Besides carrying dissolved minerals (many of which are beneficial to the consumer), water also carries suspended solids ... including a wide range of living materials including bacteria of all types and fungi (many of which are not beneficial). Water can also carry other liquids ... as an emulsion, in solution, or as a mixture. Many of these foreign liquids are not beneficial to the consumer.

So ... the water you drink, even from your kitchen faucet, may have many contaminants that are not beneficial, and, in some cases, bad for you. In 1993, NBC's television program "DateLine" documented just this fact. Concerns with public water treatment systems in Milwaukee and New York were given as examples of failure to remove potentially deadly organisms from drinking water. The Berkey^® filters have been shown to be capable of removing the specific organism named in the program, Cryptosporidium, from water.¹ The following pages deal with some of the contaminants often found in drinking water.