Systems for reverse osmosis produce water relatively gradually. Because of this, they have a storage tank so that RO water is available when you need it. A diaphragm separates the two chambers (for air and RO water) inside the hydro-pneumatic tank. Air compresses when water fills the tank, creating energy that forces water out of the tank and towards your tap. The RO membrane experiences resistance from this energy, which slows the flow of water. As production decreases, the system becomes less effective as the ratio of water to drain rises.
The Permeate pump establishes a barrier between the tank and the RO membrane to prevent production from being impacted by the rising tank pressure. It drives the pump that dispenses RO water into the tank using the water that is draining. This improves effectiveness, keeps the drain ratio low, and enables the membrane to produce water of the highest quality. Consider attempting to enter a room while someone is pounding on the door from the opposite side. After much struggle, you might finally succeed, but it will be lot simpler if you have more allies at your side. The permeate pump functions as that extra force that the membrane needs to overcome resistance.
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