mrsell63, you are exactly correct. The "filters" that are sold to softer our homes' water aren't filters at all, they are ion exchange resins. True, they take out Calcium, Iron etc which result in hard water but the metal ions have to be replaced with another metal ion, mother nature doesn't like to allow electrically charged anything, much less water. So the Calcium, Iron and other ions in regular tap water are replaced by Sodium ions and so you are drinking dissolved Sodium ions which we all know is bad for one's health and is more corrosive that the metal ions it removed. If you buy the more expensive Potassium ion exchange resins the bad effects to your health are averted but the water still is quite corrosive. I drove a girl salesperson crazy one evening with all this. she finally left in tears. That's the kind of amusement that PhD chemists enjoy!!!