Before it hits your tap, unfiltered water from the Catskills winds its way through 6,000 miles of pipes aqueducts and tunnels.
Most of New York City's water -- 90 percent -- comes from the Kensico Reservoir. It holds 30 billion gallons and then travels to the ultra violet treatment facility in Westchester County, where 12,000 bulbs treat 1 billion gallons of water a day.
Hope this helps
