Flushing toilets represent the largest portion of indoor water use.
Unless they are newer models, most toilets use 3.5 to 7 gallons of water each time they flush. This is to remove a relatively small amount of waste. Modern, high-efficiency toilets use only 1.6 gallons per flush. In most homes, about one-third (33%) of the water used goes to flush toilets.
You can save water by making sure that you don't use the toilet as a trashcan for paper and particles that can be thrown in the garbage can instead. Why waste gallons of precious water if you don't have to?