Everytime I try to learn about water chemistry with regards to brewing I just always seem to end up confused and frustrated.
I understand the concept of appropriate ranges of minerals, and pH ranges, but it's putting that information into execution in a mash that I just start to get confused.
Here is my most recent water report levels:
Ca - 65 mg/L
Hardness [as CaCO3] - 246 mg/L
Mg - 21 mg/L
Na - 77 mg/L
Alkalinity - 112 mg/L (My water report doesn't show Bicarbonate HCO3)
SO4 - 160 mg/L
Cl - 78 mg/L
When I put these numbers into the equation in Ray Daniels' "Designing Great Beers" book
pH = (CaCO3 x 0.056) - (Ca x -0.04) - (Mg x -0.033]) x 0.028 + 5.8
I get an approximate mash pH of 6.1
The only way I seem to be able to calculate a mash pH of 5.4 (and still stay within ideal ranges of Ca and Mg) I would have to start with a negative amount of CaCO3 (which i assume means an acidic water)... this is where I begin to become frustrated. Can you even have negative CaCO3?
im confused...

Also, could anybody further explain to me using R/O Water vs. Distilled? At least as far as how the differences apply to brewing...