brooklyn1 wrote:
>
> Bryan wrote:
> >brooklyn1 wrote:
> >> Horsepucky. Water softeners do not add salt to water
> >
> >Of course they do. You must be thinking of reverse osmosis filters,
> >not water softeners. They exchange sodium for calcium and magnesium.
>
> Water softeners do not exchange minerals for salt. Brine enters the
> softener tank only (in concentration set based on hardness testing and
> at times set by a clock and gallons used, typically after every 3,000
> gallons and in the middle of the night to prevent pressure drops), and
> removes the minerals collected by the beads, and minerals and brine -
> salt is a mineral - is flushed out as grey water... none of the grey
> water enters the domestic water. Salt can only enter the water
> system (along with the minerals) when the unit is malfunctioning. Also

The function of the brine is to displace the minerals
collected by the resin. Resins have functional groups
which can bind metals like iron and sodium. A recharged
resin will be holding sodium on those groups, and the
metals in water have higher affinity for those groups
than sodium, so they displace the sodium (which then
goes into the house water).

When the resin becomes loaded with metals, the brine
recharges the resin by displacing the metals with
sodium. Even though the metals have higher affinity
for the resin, you overcome that by using a much higher
concentration of sodium, i.e. the brine. Most of the
brine (along with the metals) is flushed to wastewater.
The sodium held by the recharged resin ends up in the
house water.