Sadly i have never seen RO or distilled water around these parts in europe sold in big quantities. (i could get distilled in pharmacies for like 15$ per gallon but that is too expensive) (also RO machines are almost unheard here, i am jelly in so many ways of you US guys)
On the other hand this lime method looks pretty good. I am planning a brewday on the weekend, should i try this alkalinity reduction method with heat (boiling) instead of lime until i can get food grade lime?
Does the CaCl or CaSO4 into water to get enough calcium ---> 10 minute boil ---> 1 day settling time ---> racking from the top method works?
The lime method looks much cheaper and easier but pickling lime is quite rare here and i only found chemistry shops selling it.
Sorry glue, didn't know... Lime is the way to go, even if it's pricey as a little goes a long way. Your strategy for boiling looks sounds but the actual reaction is not perfect. How hard/long to boil, reaction requires CO2, etc. Yes, the Ca salts should easily dissolve and help the reaction. I only tried lime and even that was "fun". Some more info: https://www.homebrewersassociation.org/forum/index.php?topic=5792.0