According to the Energy Policy Act, if your toilet was manufactured before 1992 chances are its wasting water. The Energy Policy Act required all new toilets to be low flow, restricting water usage to a maximum of 1.6 gallons per flush instead of the old average of 3.5 gallons. Think about the money you would save on your water bill!
At the end of the day, if all inefficient toilets in U.S. homes were converted to water sense models, we would save 640 billion gallons of water per year. This is equivalent to 10 days of flow of the Niagara Falls.