A water softener filter is a device used to purify water. In more complex terms, water can be both "hard" and "soft." Hard water is unfiltered and contains contaminants such as calcium and magnesium. When water is vaporized, these contaminants are left behind, which can result in serious damage to the vessel that contains them. A water softener filter uses a chemical process to remove and replace these harmful components of hard water; a process known as "softening."
Most of the time, water isn't entirely pure. In a lot of cases, there are many contaminants and particles mixed in with the water that cannot be seen with the naked eye. When water is heated or converted into steam, also known as vaporization or saturation, these particles are left behind. For example, if salt water was boiled to a point in which all the water was vaporized, the salt that was once in the water would be left behind. There are, however, far more harmful particles than salt in hard water.
Two of the most harmful contaminants found in hard water are calcium and magnesium. When water is vaporized or heated, these are left behind, resulting in something called "scale." Scale is a harmful, hard substance which consists of the precipitate — anything solid left behind after a chemical reaction — of both magnesium and calcium. Scale can be found in any vessel that heats hard water, including pipes, tea kettles, and steam boilers.
Scale can present a number of problems for water pipes and boiling vessels. For pipes that heat or boil water, one of the most common issues that scale can create is clogging. Scale can build up to a point where it completely clogs the pipe, causing problematic backups. Scale is also a problem in boiling vessels, due to the fact that it cannot conduct heat well. Due to this, scale built up in tea kettles and boilers can cause serious damage as a result of overheating.
When a water softener filter is used, sodium ions replace the calcium and magnesium ions, thus preventing the formation of scale. The replacement process occurs when the hard water flows through sodium ion-coated plastic beads or zeolite, which is an adsorbent mineral that is also coated with sodium ions. When hard water passes over either of these, the sodium ions replace the magnesium and calcium ions, therefore softening the water. Filters must eventually be replaced or regenerated with a strong sodium solution, such as salt water.
There are a variety of other purification options available, including distillation and reverse osmosis. These processes, however, are often too expensive to justify for small-scale private use. A water softener filter is far less expensive and serves as a more economically viable water softening device.