I just started getting into water chemistry and purchased a TDS meter. The TDS of my starting water (RO and deionized) is 2 ppm. I added 48.8 ppm Ca, 5.2 ppm Mg, 15.4 ppm Na, 57.4 ppm SO4, 63.9 ppm Cl, and 32.6 ppm HCO3. How can I calculate a TDS from this? If I add up those additions (and...