The way it works is that rebuttals need only be at the level of evidence of the initial claim. Hitchen's Razor: "what is presented without evidence may be dismissed without evidence."
His claim is absurd on its face, due to the small quantity of minerals actually in water, compared to what is required. Food must be providing most of that input.
I'm curious where this nonsense came from. It feels like another variety of nutrition superstition.
I mean, not OP, but you're the one who made the initial assertion. Maybe you should be the one providing published evidence?