<P> When a user flushes a toilet , a `` toilet flapper valve '' ( not to be confused with a type of check valve ) opens and allows water from a reservoir tank to quickly enter the toilet bowl . This rapid influx from the tank causes the swirling water in the bowl to rapidly rise and fill the U-shaped inverted siphon tube mounted in the back of the toilet . This full siphon tube starts the toilet 's siphonic action . The siphon action quickly ( 4 -- 7 seconds ) `` pulls '' nearly all of the water and waste in the bowl and the on - rushing tank water down the drain -- it flushes . When most of the water has drained out of the bowl , the continuous column of water up and over the bottom of the upside - down U-shaped drain pipe ( the siphon ) is broken when air enters the siphon tube . The toilet then gives its characteristic gurgle as the siphonic action ceases and no more water flows out of the toilet . After flushing , the flapper valve in the water tank closes ; water lines and valves connected to the water supply refill the toilet tank and bowl . Then the toilet is again ready for use . </P>
where does the water from the toilet come from
water lines and valves connected to the water supply