On Tue, 12 Jan 2010 21:32:01 -0500, brooklyn1
> wrote:

>sf > wrote:
>>
>>How water softeners work
>>http://home.howstuffworks.com/question99.htm
>
>That's much more an over simplified course on how to install a water
>softener than it is about how water softeners work.
>
>The thing to keep in mind is that virtually all tap water contains
>salt. In the process of softening water whatever miniscule quantity
>of salt a softener may add it's less than it removes so the net result
>is that ones tap water will contain less salt after softening... and
>we're talking about 10 mg or less per liter, which is less salt than
>is contained in a liter bottle of sody pop that's permitted to list 0
>mg sodium. Virtually all naturally ocurring water on the
> planet contains salt, even rain water. Technically a water softener
>can add some salt, but less than it removes. A human being can't
>drink enough softened tap water to even come close to ingesting too
>much salt. We get our salt from food, all food naturally contains
>salt, and of course from salt shakers.
>

Water softeners that use rock salt will add sodium to the water,
period. Each gram of magnesium ions present in hard water will result
in 1.89 g of sodium ions replacing the magnesium. Each gram of
calcium ions, 1.15 grams of sodium ions. That's why it's called "ion
exchange."

As others have noted, use of potassium chloride in the water softener
in place of sodium chloride will give a mixture of sodium and
potassium ions in the water---somewhat better for consumption.

Moderately hard water may contain about 100 mg of Ca ions per liter.
After ion exchange that water will contain about 115 mg of sodium ions
per liter. Some water in the US contains up to 250 mg of Ca ions per
liter...

From Wikipedia: A paper by Kansas State University gives an example:
"A person who drinks two litres (2L) of softened, extremely hard water
(assume 30 gpg) will consume about 480 mg more sodium (2L x 30 gpg x 8
mg/L/gpg = 480 mg), than if unsoftened water is consumed." This is a
significant amount, as they state: "The American Heart Association
(AHA) suggests that the 3 percent of the population who must follow a
severe, salt-restricted diet should not consume more than 400 mg of
sodium a day. AHA suggests that no more than 10 percent of this sodium
intake should come from water. The EPA’s draft guideline of 20 mg/L
for water protects people who are most susceptible."

"gpg" is grains per gallon, I think. All these damn different
units...

Terry