The airbag is like a balloon, which is inflated and pressurized in advance to push out the water on the upper part.
In short, the water in the bucket is pushed out by the pressure in the bucket, not pumped away.
This is the role of the air pressure inside the water storage bucket.
The more water in the bucket, the more the airbag is compressed, and the higher the pressure in the bucket.
If the pressure is high enough, it will trigger the pressure switch in the water purifier, turn off the water pump and stop making water.
When a part of water is discharged, the pressure decreases, and the pressure switch will turn on the water pump again to start water production.