Softening Ion Exchange
Why Soften Your Water?
Hard minerals such as calcium and magnesium, when evaporated from water or combined with heat, can form hard, chalky deposits known as limescale. These deposits can clog pipes, reducing flow, and coat heating elements, requiring more energy to heat water. Your operation loses efficiency, and your maintenance and energy costs rise.
There are different means of treating scale, such as phosphates, reverse osmosis and softening. Each treats for scale differently, for example phosphates keep mineral suspended in solution, reverse osmosis removes mineral, and softening exchanges hard mineral for soft mineral (such as sodium). Softening provides both advantages and disadvantages. An advantage is a maintained softener can provide hardness removal for many years and models can handle high volumes of water. A disadvantage is sodium must be added to the brine tank on a regular basis.
The Ion Exchange Process
Softening is the process of ion exchange. The ions in hard minerals (calcium and magnesium) are exchanged with ions of “soft” minerals such as sodium, which do not produce the hard scale that can damage foodservice equipment.
Water softener systems consist of two tanks: a resin tank and a brine tank. The resin tank contains a bed of negatively charged cation resin beads that are coated with sodium (Na+). As hard water passes through this bed, the positively charged calcium (Ca++) and magnesium (Mg++) ions are attracted to and adhere to the resin, causing the sodium ions to release into solution. The calcium and magnesium in the water has now been exchanged for sodium. Since the sodium in the water is harmless to plumbing and equipment, the “softened” water is now ready for use by the operation.
During the exchange process, the sodium charge eventually depletes. When near depletion, the softener is regenerated to recover the exchange capacity. To remove the calcium and magnesium from the beads, high concentration sodium solution from the brine tank is drawn through the resin bed. The sodium ions in the solution displace the calcium and magnesium ions, releasing them back into the solution. The sodium in the water has now been exchanged for the calcium and magnesium. These hardness ions are then flushed down the drain.
It’s important to understand that a water softener does not filter water, it only exchanges hard ions for soft ions. For removal of dirt, chemicals and organics, a filtration system should be used.
Measuring Grains of Hardness
Hardness of water is measured in grains per gallon (GPG) or sometimes in parts per million (PPM). One GPG equals 17.1 ppm (Mg/l). Generally water with GPG of 7 or more is considered hard. To determine the hardness of your water, it can be tested using simple test strips or a titration drop test. Everpure can provide an analysis of your water to determine the correct water treatment solution for your operation.
Water Grains / Gallon Mg / l or ppm
- Soft < 1.0 0 - 17.1
- Slightly Hard 1.0 - 3.5 17.1 - 60
- Moderately Hard 3.5 - 7.0 60 - 120
- Hard 7.0 - 10.5 120 - 180
- Very Hard > 10.5 180 +
Are All Applications Suitable for Softened Water?
Generally softened water is recommended for:
- Iced tea
Espresso machines boil water at a very high temperature and pressure, much more so than coffee brewers. Because of this, hard water will create scale at a very fast rate in espresso machines. Normally softened water causes over extraction of the coffee grounds, which is why it is not used with coffee brewers. However, because extraction time is so short with espresso, it does not cause the same problem. Hard water can cause iced tea to become cloudy. With warewashing applications, hard water causes spotting on glassware and excessive detergent usage.
Water softening is not recommended for:
- Ice making
- Coffee and tea brewing
- Fountain beverages
Soft water can slow the freezing process in ice making. With coffee and tea brewers soft water can over extract the oils and flavors in the coffee grounds or tea leaves. The major bottling companies have also asked water treatment professionals to avoid the use of water softeners with fountain beverage equipment because softened water can affect the taste profile and cause excessive foaming.
What a Water Softener Does Not Do.
Water softeners are cation exchangers meaning they will exchange positive ions such as calcium, magnesium, iron, copper, zinc, manganese, and other metals. Water softeners to not filter water, they merely exchange hardness ions for sodium ions. Sediment, chemicals and organics that can affect the appearance, taste and odor of your water are not affected by softening your water. For these, you should consider an Everpure filtration system, or an Everpure reverse osmosis system.