Snip. Most of excellent post deleted
>Deionization in a nut shell is your home water softener. That is a bit
>oversimplified but not too far from the mark. Water is passed through a
>resin column which is designed/engineered to remove targeted ions down to
>a specified level. The resin can be selective for specific applications
>such as defluoridation or of a general type as used in a home softener.
>In general the water is not as pure as distilled water but the cost to
>deionize is much lower than distillation.
Traditional water "softeners" act by exchanging sodium ions for calcium and
magnesium ions. "Hardness" is by definition a measure of the concentration of
Mg and Ca, not total dissolved solids per se. Water that is "softened" (as
opposed to "deionized") has the Ca and Mg replaced with Na. "Softened" water
contains approximately the same concentration of dissolved substances before
and after "softening".
Water "softeners" that are in poor condition can bleed in significant amounts
of sodium _and_ chloride which will increase dissolved solids concentration.
If you have to add salt (NaCl) to your system, you have a "softener". But as
Art points out, many new systems include deionization and other treatment
that is not "softening" and actually do remove dissolved constituents.
HTH ... Marc
Marc F. Hult
hult at hydrologist dot com
hult@cinternet.net