Water softeners or whole house water treatment systems use a process called ion exchange to remove minerals from the city or well water that enters the home. This involves passing the water through a tank filled with resin beads that are coated with ions of either sodium or potassium chloride. An ion is an atom or molecule that is electrically charged. In this condition, it is capable of swapping places with certain other molecules in its environment, in this case, the “hard” minerals in the domestic water supply.
The water that enters many of our homes is hard because it contains particles of calcium, magnesium and some other minerals. The water treatment system removes most of these minerals and replaces them with either sodium or potassium salt, depending on which type you buy for your water softener.
Here are some of the pros and cons to using either type of salt. Sodium Chloride is usually less expensive than Potassium Chloride although the latter is better for the environment when your system discharges the brine solution it uses to recharge the ions on the resin beads. You can arrange to capture the discharge and use it on lawns and gardens since potassium is a key plant nutrient.
Contrary to a common misconception, using sodium salt in your water softener will not adversely affect your plumbing. Most modern plumbing is made of PVC plastic and is not affected by increased levels of either sodium or potassium chloride. Sodium salt can, however, reduce the amount of maintenance required for your brine tank.
For those concerned about how much sodium is put into the water by a water softener, the answer is, it all depends. The harder your water supply the more sodium ions are needed to soften it. That said, studies indicate that even water softened with sodium chloride has a low concentration of sodium. See this article from the Mayo Clinic for more information: http://www.mayoclinic.com/health/sodium/AN00317
The problem of too much sodium disappears if your water softener includes a reverse osmosis system which removes sodium along with other impurities.
Some concern has been expressed in a report from Health Canada about the use of potassium salts in water softeners and the potential health effects for specific segments of the population. For more information go to: http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/consultation/potassium/part1-eng.php
In the end the choice between sodium or potassium salts in your water softener is a personal one, depending on the presence of potential health issues, cost, environmental priorities and so forth.
You can have the hardness of your water tested free of charge by most companies that sell water softeners.
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