In order for the reverse osmosis membrane to function, you need a rigid pipe at atmospheric pressure, without water in it. The pressure difference inside/outsi

In order for the reverse osmosis membrane to function, you need a rigid pipe at atmospheric pressure, without water in it. The pressure difference inside/outside the pipe is what powers the desalination process. While operating, it's basically a deep open well with a bit of water at the bottom. You need to pump that water out to keep the process going.