As a practical matter, there is none. If your water tastes good, use it and don't worry. I've seen it argued that since only water molecules are removed during concentration, only distilled water should be used for reconstitution.Someone please explain the bad side effects of using distilled water - since I've used it and it's in a carboy. Thanks,
Rocky, you realize that if I was to drink a bottle of that old mead of mine that I'd probably break out in an old Carol King song...and that would just be horrible for anybody within hearing distance.<GRIN>Rusty, I am going to give you a different perspective which is in conflict with my friend, Intheswamp. I use distilled water because it is pure H2O, two Hydrogen atoms and one Oxygen atom. My feeling is when the manufacturer makes up the kit and reduces the grape juice, the only thing that is removed is pure water. The minerals of the grapes' terroir remain in the concentrate and I am only adding back the Hydrogen and Oxygen atoms that were removed.