By SOPHIA HOLLANDER New York is known for its food niche stores: The Hummus Place. The Doughnut Plant. The Dumpling Man. Even a spot dedicated solely to rice pudding. A new store in Manhattan's trendy East Village neighborhood is selling New York City filtered tap water back to city residents. For a few extra dollars costumers can add vitamins and herbal infusions to their filtered water. But this week, a store in the East Village went a step further: It sells New York City tap water. Not just any tap water, insist the owners of Molecule. They say the water streams through a $25,000 filtering machine that uses ultraviolet rays, ozone treatments and reverse osmosis in a seven-stage processing treatment to create what they call pure H20. Despite the start-up costs, it is the ideal business model, they say, since they never have to worry about spoiled products or storage costs. And then there is the taste: "I mean it's subtle, but if you have a sensitive palate you can totally tell" the difference, said co-owner Adam Ruhf.