We have drinking water with the following values:

Calcium mg/l 62.7

Magnesium mg/l 10.3

total hardness 7.) dH 11.1

Total hardness 7) mmol/l CaCO3 1,99

Carbonate hardness °dH 8.5

Hydrogen ion concentration (pH-value) - 7,8

To use the water for my plants, I reduce the pH with phosphoric acid to 6.8 PH. If I now want to find out how many calcium and magnesium ions are in the water, do I only need to read out the amount of calcium / magnesium that are listed or must the calcium from the total hardness / carbonate hardness be added too, since it was present in the form of CaCO3 / Ca(HCO3)2 and not as ions before I brought the pH Down.


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  • $\begingroup$ Looks like Houston TX water , not too bad. Some plants like it. Occasional use of rain water will help for house plants preferring neutral of acid pH. There are also acidic fertilizers., ( I use a lot of "starter" 9 -45 -15, but most of my plants like acid ).You may be able to find the chemistry of local municipalities and compare to what you have before you "fix" it. $\endgroup$ – blacksmith37 Jul 28 '18 at 20:21
  • $\begingroup$ What's your soil pH? No point titrating with H3PO4 unless soil pH is too high. If it is, powdered sulfur over winter is the usual way to handle it. $\endgroup$ – Wayfaring Stranger Jul 29 '18 at 17:45

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