[Tex Gal]

Those charts assume that the only dissolved solids you have in the water are Ca and mg (I think it's mg). Anyway... most of us have many more dissolved solids in our water supply than two, so the charts aren't a good indicator. I always begin with a dropchecker and then increase my CO2 from there. It works well.

 

[Tex Gal]

Ca & Mg have nothing to do with determining CO2. It's not about TDS either. The problem with the chart is that there can be buffers present that the KH test cannot account for and acids other than CO2 that the pH test will be effected by.

Doesn't KH measure ca and magnesium? Mine does... These charts have you measuring KH and ph and then determining the CO2 from them. Because there are other buffers (dissolved solids - ie. baking power is a dissolved solid, that changes ph, etc.) in the water it can skew your results. Maybe I'm missing something, but I only know to speak in laymen's terms.....