I've always drank water as I dont not like tea or coffee, nor do I like fizzy drinks (never liked them as a child either). Some times I drink juice but mainly plain water.
It says water should be rid of all impurities. To me, this means demineralised water which is very dangerous to drink. It will kill you! Water is a great solvent (likes to dissolve things into it). If you drink pure water it will take minerals and such out of the body! Filtered water will remove 99.9% of impurities (not all) and this is fine to drink.
I'm not sure why would would add salt to the water, as if you are dehydrated you need more than salt (potassium, magnesium and calcium come to mind), and bad dehydration needs proper hydration drinks, not just water.
Personally I think drinking water is necessary, with most people not drinking enough, and that you should check the urine colour to the wee chart to make sure you are ok (especially as it is very easy to get dehydrated with D), but as a cure I just cannot see how that would work.