Who knows how the toilet flushes it? There is an upturned bend in the back of the toilet, so how can

When the water is filled with bends that go up and then down, the water in the downward pipe falls and pulls over the other side of the bend (the part of the water you can see) that is higher than it. This bend up and down is not easy to see on the outside, and is hidden on the inside.

For example, the water in a bucket that is placed higher passes through a pipe filled with water, the outlet of the pipe is lower than the bottom of the bucket, and the water inlet of the pipe reaches the bottom of the water in the bucket, so that the water in the bucket will flow along the pipe, over the edge of the mouth of the bucket higher than the liquid level, and flow to the lower place outside the bucket, that is, up first and then down, until all the water in the bucket is gone. This is called siphoning.

There is an upward curve at the back of the toilet to cause negative pressure in the air, just like an airplane flying in the sky, it is not allowed to have a certain speed forward, otherwise, the negative pressure is too low and it will fall. The same is true for the toilet, it does not bend, it can't create negative pressure, it can't pump water, it can only run water.

The flush toilet is a physical siphon principle, that is, when the water surface is higher than the elbow, the water will siphon out, and the water in the storage bucket will be sucked out, just like using a hose to suck the water in the fish tank at home!

It's called a reverse bend to prevent odor from entering the room.

This bend is a water seal, so that the water storage seals the odor in the pipe and does not keep it indoors.