I heard that a surprising sentence from a restaurant chef in San Antonio. “Since we are using a water softener, our water is clean.” I asked him if the restaurant is using some filtration systems and he said it is not.
Because San Antonio’s ground contains lime stones, its water is very hard. The hard water is mentioned here in the past blog. Therefore, many restaurants are using water softeners in San Antonio.
Do water softeners purify water? The answer is "NO." So, the restaurant chef’s statement is incorrect. Today, I would like to mention the misunderstanding about water softeners people tend to feel.
If the definition that water is clean is that the dissolved solids are small, softened water passing through water softeners contains more dissolved solids compared with tap water.
The water softener softens water with Na-type strongly acidic cation exchange resin. The resin absorbs calcium and magnesium of water and releases sodium. This is called "iron exchange". So, water softener does not purify water at all.
Let’s mention more details. When resin is new or regenerated, it holds sodium which has one valence. Water containing calcium and magnesium pass through the resins, the resins absorb the calcium and magnesium which has two valences and release sodium which has one valence because two valences make more absorbed.
When the resins hold maximum calcium and magnesium, it cannot absorb the calcium and magnesium. In this case, water softener’s valve pours salt water into its tank from the brine tank and calcium and magnesium are released and sodium sticks on resins. This process is called “regeneration.” Therefore, water softeners need salt to be regenerated.
If the water in the brine tank is dirty, the dirty water goes into the water softener’s tank directly. There is no process to purify water so, in general, the softened water after passing through water softeners has more particles than tap water.
Also, softened water has more sodium than tap water. Sodium sometimes causes the disease of high blood pressure and so on. Since the amount of sodium is very small, we do not have to worry about the disease, but we have to know the softened water contains sodium when we drink water in restaurants and at home.
Therefore, softened water passing through water softeners is not clean. Generally, the softened water’s TDS is higher than tap water’s.
How to reduce TDS? The solution is to use reverse osmosis systems. The RO is mentioned here in my past blog.