We were buying this for San Pellegrino.
https://www.amazon.com/Burton-Water-Salts-1-lb/dp/B0064OGFXW/ref=cm_cr_arp_d_product_top?ie=UTF8
And then i found this site, downloaded the Excel spreadsheet and started mixing the salts. I was able to buy them off amazon. I've been making up enough for 100 L at a time.
https://blog.khymos.org/2012/01/04/mineral-waters-a-la-carte/
BTW, some of the salts come in little spheres or fairly large crystals. You have to run them through a spice grinder. And, yes we carbonate the water, then add the salts, which can be interesting with the reaction you get. Got to be quick getting the cap on.
