According to Scott Tissue, during the halftime of the SuperBowl (or the Big Game as they call it, to avoid infringing on the NFL's trademark) "more than 350 million gallons of water will flush through our toilets as an estimated 90 million people use their facilities. That amount of flushing equals seven minutes of water flowing over the Niagara Falls."
Actually, they admit that this is a legend, but they've created a website to cash in on the legend: halftimeflush.com
. However, I don't know how they arrive at the figure of 350 million gallons. (I assume they're just making up the figure of 90 million people flushing the toilet.) I thought that the average toilet uses about 2 gallons per flush. In which case, the volume of water used would be closer to 180 million gallons... and so equivalent to only about 3 1/2 minutes of water flowing over Niagara Falls.
But where are they getting their facts about the volume of water flowing over Niagara? According to this site
, 150,000 gallons per second flows over the American Falls, whereas 600,000 per second flows over the Canadian falls. So, assuming that they're talking about the Canadian falls, 350 million gallons of water flushed down the toilet would be equivalent to almost ten minutes of water flowing over Niagara.