Oh well there are many different ways to purify water and it depends what technology is used to filter heavy metals and e-coli and other deadly Bacteries out of water . You will get either reverse osmosis or distilled ( not so good because flat ) or purified water . None of those are considerd "hard" but clean . The so called "mineral water" is usually only treated with ultraviolet radiation therefore most heavy metals still packed up in those horrible plastic bottles . I should write an article about this topic because I spent 5 years of my life to study this fascinating element of life !