Your toilet may have a leak, and you may not even know it. Drop about 6 drops of red, blue or green food dye into the tank of the toilet (the part with all the levers and valves) and wait an hour or so. Come back and see if the water in the toilet bowl has changed color. If you see any color, your toilet is leaking water and wasting countless gallons of H2O annually. Call a plumber and get it fixed.