This is a participatory experiment, and all friendly participation is welcome. I'm attempting to see how well an educated guess based solely upon the ppm data derived via a budget hand held TDS meter might do at ballpark predicting ones Ca++ and Mg++.
Apply this method and provide feedback as to how close it gets you to "known" values for your waters calcium and magnesium:
Total Hardness (as CaCO3) ~= 0.78 x ppm_TDS (as read via the TDS meter)
Total Hardness (as CaCO3) = 2.5(Ca++) + 4.12(Mg++) (this, with the constants rounded, is a truism)
~70% of Total Hardness comes from Ca++ (on loose average/approximation for fresh water)
~30% of Total Hardness comes from Mg++ (on loose average/approximation for fresh water)
Example: Lets say your budget hand held meter says your TDS is 400 ppm
400 x 0.78 ~= 312 ppm Total Hardness (as CaCO3)
0.70 x 312 = 218.4 = the ~hardness that comes from Ca++
0.30 x 312 = 93.6 = the ~hardness that comes from Mg++
218.4/2.5 = 87.4 ppm Ca++ (calcium ion)
93.6/4.12 = 22.7 ppm Mg++ (magnesium ion)
This presents an admittedly loose ballpark stab at deriving a source waters calcium and magnesium ppm from only a TDS meter. It's akin to educated guessing, but that is sometimes better than uneducated guessing. There is clearly room for refinement, but data feedback is my only means of garnering the data from which to refine this approach.
Apply this method and provide feedback as to how close it gets you to "known" values for your waters calcium and magnesium:
Total Hardness (as CaCO3) ~= 0.78 x ppm_TDS (as read via the TDS meter)
Total Hardness (as CaCO3) = 2.5(Ca++) + 4.12(Mg++) (this, with the constants rounded, is a truism)
~70% of Total Hardness comes from Ca++ (on loose average/approximation for fresh water)
~30% of Total Hardness comes from Mg++ (on loose average/approximation for fresh water)
Example: Lets say your budget hand held meter says your TDS is 400 ppm
400 x 0.78 ~= 312 ppm Total Hardness (as CaCO3)
0.70 x 312 = 218.4 = the ~hardness that comes from Ca++
0.30 x 312 = 93.6 = the ~hardness that comes from Mg++
218.4/2.5 = 87.4 ppm Ca++ (calcium ion)
93.6/4.12 = 22.7 ppm Mg++ (magnesium ion)
This presents an admittedly loose ballpark stab at deriving a source waters calcium and magnesium ppm from only a TDS meter. It's akin to educated guessing, but that is sometimes better than uneducated guessing. There is clearly room for refinement, but data feedback is my only means of garnering the data from which to refine this approach.
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