Just water is a poor way of getting hydrated, as many have found.
There was the runner in the Boston Marathon who died; not enough electrolytes in his blood to keep the heart beating.
I drink distilled water, but always add for 2 litres:
1 or 2 teaspoon pickling or canning salt (close enough to pure salt - do not use table salt).
1 teaspoon vit. C as ascorbic acid
1 teaspoon potassium chloride
1 teaspoon citric acid.
This from the VWT Iodine forum at curezone.com, where it is known as IMAM - for Improved Miracle Adrenal Mixture.