Hard Water Explained

As rain falls through the atmosphere, it often adsorbs traces of acidic gases from the air (carbon dioxide, sulfur dioxide, etc.)- When the water reaches the ground, it percolates through the soil and dissolves certain soil components. The greater the acidity of the rain water, the more soil material dissolved. Ground waters (wells, springs) and surface waters (rivers, lakes, oceans) contain a certain amount of dissolved matter. Many of these substances are chemical compounds, which can dissolve in water to form electrically charged particles called ions.

Two of the most commonly occurring ions in natural waters are calcium and magnesium. Both are positively charged ions called cations, and each carries two unit charges. The presence of these two minerals in natural water causes "hardness", which produces a scum or curd with soap, and forms a hard scale in piping and water heaters. Other cations present in natural waters may include sodium, potassium, iron and other metallic components, but primarily calcium and magnesium make water "hard".

Softening Explained

Problems associated with hard water can be minimized by using a water softener. Conventional softeners operate on the principle of ion exchange. The most common ion exchange method used today is the sodium cycle operation. In this process, calcium and magnesium ions are removed by exchanging places on an ion exchange resin with sodium. This process is commonly known as positive ion or cation exchange. Negatively charged ions from the source water remain. Softening does not reduce total dissolved solids; it exchanges the "troublesome" hardness ions for sodium ions.

To avoid potentially coating the ion exchange resin with colloidal or suspended material, clear water should be applied to the softener. Water supplies containing very high amounts of other ions or contaminants may need to be pretreated before being applied to a softener.