The lime-soda method of water softening must be followed by sedimentation and filtration in order to remove the precipitates. By doing this, the water softening removes the offending minerals from the water. As a result of the poor heat conductivity of the scale, fuel consumption is increased, and the boiler deteriorates rapidly through the external overheating of the plates. Corrections? Eliminating or reducing water hardness is done with a piece of equipment known as a water softener. The third main component of a water softening system is the brine tank. It can also leave hard water stains on bathtubs or sinks and clog pipes. For every grain of hardness removed from water, 8 mg/1 (ppm) of sodium is added. Water softening is a process in which the ions of calcium, magnesium and sometimes iron are removed. Water softeners have to primary functions; the Softening cycle and the Regeneration cycle. A third type of control uses a mechanical water meter to measure water usage and initiate recharging. Water softening, the process of removing the dissolved calcium and magnesium salts that cause hardness in water. The brains of the softener lie in the control valve or softener head as it is commonly referred to. It is achieved either by adding... Save 50% off a Britannica Premium subscription and gain access to exclusive content. This article was most recently revised and updated by, Most typically the ions are exchanged with ions from dissolved sodium chloride salt (brine). Hard water is water that has high dissolved mineral content (as opposed to soft water having a low dissolved mineral content). SOFTENING: AN OVERVIEW. Most popular water softeners have an automatic regenerating system. Typically, these resins are based on cross-linked polystyrene. Conventional water softening is most often based a process known as ion exchange, utilizing a synthetic polymeric (plastic) material in the form of very small beads called ion exchange resin. These softeners often have reserve resin capacity, so that some soft water will be available during recharging. Multivalent cations are cations (metal ions) with a charge greater than 1+, mainly 2+. The most basic type has an electric timer that flushes and recharges the system on a regular schedule. Water softening is thus indispensable in many industries, and small water-softening units are used in homes in a number of countries. As hard water passes through the resin, hardness ions (Ca2+ & Mg2+) are physically exchanged with the sodium ions on the ion exchange resin. In boilers, the calcium and magnesium in hard waters form a hard adherent scale on the plates. Hard water—caused by the presence of calcium and magnesium ions, which form insoluble precipitates with soaps—is softened by exchanging its calcium and magnesium ions with sodium ions. During recharging, soft water is not available. From the lack of suds formation in bathing and laundry applications to the costly breakdowns in boilers, cooling towers and other equipment that handle water, water hardness is a serious issue. The salt or potassium chloride is a sacrificial media and must be replenished on a regular basis to ensure adequate softening form the device. The presence of certain metal ions like calcium and magnesium principally as bicarbonates, chlorides, and sulfates in water causes a variety of problems. At first, the exchangers used for this purpose were natural aluminosilicates, but later, synthetic resins came to be used instead. Hardness in water is defined as concentration of multivalent cations. Rainwater and distilled water are soft, because they contain few ions. Hard water flows through the resin beads; Sodium is swapped for hard water minerals; Did You Know? This process continues until the resin becomes saturated with hardness ions and depleted of sodium ions. This resin is basically an insoluble matrix typically in the shape of small (1-2 mm diameter) beads. These cations include Ca2+ and Mg2+. Unlike hard water, softened water will not form insoluble scale or precipitates in pipes and tanks or interfere with cleaners such as soap. Hard water is typically found in ground water (wells) as the water is in direct contact with minerals which can be dissolved. When Ca 2+ and Mg 2+ ions containing hard water is passes through a bed of sodium zeolite, the sodium ions are replace by the calcium and magnesium ions. This brine (a concentrated solution of salt water) is drawn back into the mineral tank during the regeneration phase to replenish the softener bed. Omissions? Hard water is any type of water that contains more minerals than average tap water. The total water hardness, including both Ca2+ and Mg2+ ions, is reported in parts per million (ppm) or mass/volume (mg/L) of calcium carbonate (CaCO3) in the water. By doing this, the water softening removes the offending minerals from the water. The heart of the softener is the mineral tank which is a pressure vessel usually constructed out of fiberglass. The advantage of this system is that no electrical components are required and the mineral tank is only recharged when necessary. Hard water is generally not harmful to one's health but can pose serious plumbing problems in both residential and commercial applications. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. These tanks are filled with negatively charged ion exchange resin. People on restricted sodium intake diets should account for increased levels of sodium in softened water. When enough water has passed through the mineral tank to have depleted the beads of sodium, the computer triggers regeneration. Hard water has high concentrations of calcium (Ca2+) and magnesium (Mg2+) ions. When it is equipped with two mineral tanks, softened water is always available, even when the unit is recharging. Mostly it has to do with elevated levels of calcium and magnesium, which can make it difficult for products like soap to dissolve in the water. On a small scale, chemicals used for softening include ammonia, borax, calcium hydroxide (slaked lime), or trisodium phosphate, usually in conjunction with sodium carbonate (soda ash). If you have hard water, a water softener is the solution to spotty dishes, dry skin and limescale buildup in pipes and appliances. It is these ions in hard water that make it difficult for products with other positively charged ions to dissolve in the water. It is inside this softener where the ion exchange process occurs. Water softening is a process in which the ions of calcium, magnesium and sometimes iron are removed. Ion exchange resins can be manufactured to selectively prefer one, or perhaps several different types of ions. After the column has been in use for some time, calcium and magnesium begin to appear in the water leaving the column. Although water hardness usually measures only the total concentrations of calcium and magnesium (the two most prevalent divalent metal ions), iron, aluminum, and manganese can also be present at elevated levels in some locations. Hardness can be quantified by instrumental analysis. You can live with the hardness level, recognizing that levels below 7.0 gpg will probably not cause major scaling and soap film, or treat the water to reduce the calcium and magnesium present.A water softener, also called an ion exchange unit, will effectively accomplish the latter option. At that point, the column must be regenerated by passing a concentrated solution of common salt slowly through the column; the excess sodium ions displace the ions that produce the hardness so that, after flushing with water, the bed of exchanger is ready to be used again. Home water softeners usually work similarly and consist of zeolite or another ion-exchange resin in a tank connected directly into the water system.