I live out in the stix..
got me a well...
its 145 feet deep, and the water still stinks...
My understanding is that the brine tank is only used in the regeneration of the ion-exchange resin, not the actual softening process. The ion exchange is one step and the water passing through the resin goes right out. So bascially...
H2O with Mg2+ and Ca2+ ions go in, H2O with Na+ or K+ ions go out. Keep in mind that you need two "soft" ions to replace each "hard" ion. The sodium added depends on the hardness of the water entering.
Once the resin is depleted of sodium (or potassium) a separate solution of aqueous salt from the brine tank is flushed back in thus the previously trapped magnesium and calcium are drained out and the resin is recharged with the salt. This is commercial salt added to the tank which in turn the sodium is eventually entering the water supply.
http://home.minneapolis.edu/~boraaski/C1152%20Handouts/7.%20Water%20Hardness%20Determination%20v.1.09.pdf
http://home.howstuffworks.com/question99.htm
http://archinte.ama-assn.org/cgi/content/abstract/157/2/218
http://www.qualitywatertreatment.com/faqs_water_softeners.html#7
http://home.howstuffworks.com/question99.htm
Why are people who actually understand some basic science nerds? I often wonder. To me, the "nerds" are people who can remember who plays for which football team; a totally useless collection of information.