Technically, the term “water treatment” refers to any modifications made to raw water (water from the original source, i.e. rivers, lakes, streams, etc.). Included under the umbrella term “water treatment” are both water softeners and water filters. For this reason, the functions of the two different technologies are often seen as interchangeable.

Water filters and softeners do, in fact, serve very different purposes. The main goal of a water filter is to provide clean, contaminant-free water for drinking and other purposes. The main goal of a water softener is to remove “hardening” minerals like calcium and magnesium from the water. Water softeners do not remove dangerous chemicals or bacteria.

Water is termed “hard” if it contains large amounts of dissolved calcium and magnesium. Hard water causes two major problems. First, it can initiate scaling on the inner surface of pipes, water heaters, and/or tea kettles. When scaling occurs, the calcium and magnesium separate from the water and form a hard, thin layer on the inside of such appliances, causing the appliances to clog and reducing their ability to conduct heat. Second, hard water causes soap scum to build up on dishes and tile. Hard water also reduces the soap’s ability to lather.

In order to remove calcium and magnesium from water, water softeners chemically replace the calcium and magnesium ions with sodium ions. Because sodium does not separate and scale on pipes or react badly with soap, both problems of hard water are solved. From a health perspective, calcium and magnesium are better and healthier for our body systems than sodium. Water filters will generally solve the same problems as water softeners, without adding sodium to the water.

Source: http://www.historyofwaterfilters.com/