2007 estimate f households: 111,162,259 (http://www.census.gov/population/projections/nation/hh-fam/table1n.txt)
average annual household water use: 127,400 gallons
percentage used for toilets: 26.7% = 33,124 gallons per household per year (http://www.toiletabcs.com/toilet-water-conservation.html)
Sooooo,.... 33,124 * 111,162,259 = 368,213,866,716 = 368 billion gallons per year saved by using this method if everyone in the US does it.
===================================================== overview if video not working: put a bucket over your bath tub drain so that while you take a shower it will fill with water splashing off of you. when full set bucket aside and use the water to flush your toilet by pouring the water directly over the toilet drain til everythings flushed away. You can do this using a very small amount of water from the bucket if you aim right and hold it high enough (the force of the water falling into the drain sucks everything away).