I know how much based on personal experience, it differs per person of course, but I add half a teaspoon of pink himalayan rock salt per pint of water (Which is like 18oz). Sometimes more since my diet is low carb (and the water I drink is distilled), most of the foods I eat contain little to no sodium, so I'm always liberally salting my meals (and my water :p), Trust me you don't want to experience hyponatremia, not fun.