Permeate pump and waste water:

If you have a RO system without pressure tank, then you need to use electrical booster pump like Aquatec 6800 or 8800. The permeate will save water when the system is connected to a pressure tank. The purpose of the permeate pump is to help pushing purified water into the storage tank.

When the tank is empty the pressure inside the tank is about 7 psi, then when the water is filling up the pressure increases and the back pressure from the tank is pushing against the RO system so it becomes harder and harder to push water into the pressure tank, and this is where the inefficiency comes in. Therefore, by using a permeate pump, it helps to push water into the pressure tank it will fill up the tank faster thus reduce the overall waste. If you are just measuring the amount of drain water, the amount of drain is the same in 5 minutes, but if you test for the times it takes to fill up the pressure tank, that it makes the system fill up the tank 30% faster then the system shuts off and stop draining, then the saving of drain water is apparent.