What should good drinking water contain?

Answer 1

A uniform solution of dihydrogen monoxide. Seriously though, good drinking water is best defined by what is not in it rather than what is. Heavy metals, such as lead or cadnium should not be present. Nitrogen levels (from fertilizer runoff) should also be low. Arsenic should be nonexistent Bacteria and other organisms should also not be found. Generally, water meeting federal quality standards (basically anything you'd get out of a tap in the US) is "good drinking water". While products might have you believe they contain "essential trace minerals" or added oxygen or the like, there's no evidence to suggest these are superior to plain tap water.