how much water do toilets hold
Mounted above the toilet is a large holding tank with approximately 1.2 to 1.6 U.S. gallons (4.5 to 6.1 L) of water in modern designs. This tank is built with a large drain 2.0 to 3.0 inches (5.08 to 7.62 cm) diameter hole at its bottom covered by a flapper valve that allows the water to rapidly leave the holding tank.