I'm looking for a water container that functions like the one on the bottom, as water flows out of the container, the "cap" goes down, no air gets in. I don't know what it's called or what keywords to use. English is not my native language.
I need it so I can increase the water flow rate of the container by placing a weight on the cap.
I'm aware of alternatives, I'm just interested in this particular setup, just a tank, with a weight placed on top to increase flow rate. Any help?
P.S., ignore all the other parts in the image, it's just an image I came by in a physics forum and it include the part I want.