One should also know that the softener removes Ca and Mg (as pointed out), but does not remove Bicarbonate. If you have high levels of Bicarbonate in the softened water, it is then even less suited for brewing - like my softened water.
Exactly.
Here's what mine looks like out of the softener:
pH 7.4
Total Dissolved Solids (TDS) Est, ppm 265
Electrical Conductivity, mmho/cm 0.44
Cations / Anions, me/L 5.0 / 5.2
ppm
Sodium, Na
114Potassium, K < 1
Calcium, Ca < 1
Magnesium, Mg < 1
Total Hardness, CaCO3 < 1
Nitrate, NO3-N 1.1 (SAFE)
Sulfate, SO4-S 3
Chloride, Cl 6
Carbonate, CO3 < 1
Bicarbonate, HCO3
291Total Alkalinity, CaCO3
239"<" - Not Detected / Below Detection Limit
And out of the hard water tap:
pH 7.6
Total Dissolved Solids (TDS) Est 274
Electrical Conductivity, mmho/cm 0.46
Cations / Anions, me/L 5.2 / 5.1
ppm
Sodium, Na 7
Potassium, K 5
Calcium, Ca 77
Magnesium, Mg 10
Total Hardness, CaCO3 234
Nitrate, NO3-N 1.0 (SAFE)
Sulfate, SO4-S 3
Chloride, Cl 5
Carbonate, CO3 < 1
Bicarbonate, HCO3
287Total Alkalinity, CaCO3
236"<" - Not Detected / Below Detection Limit