Right. Ultra-pure water is, indeed, extremely pure ... but even tap water is already very pure by the standards of blood, or intra/extra-cellular fluid. The dif

Right. Ultra-pure water is, indeed, extremely pure ... but even tap water is already very pure by the standards of blood, or intra/extra-cellular fluid. The difference between UPW and tap water is nowhere near enough to make it dangerous to drink, save in quantities that are already objectively dangerous to drink tap water: osmotic pressure depends on differences in concentrations, not the absolute level of purity.