The problem with using
standard systems for commercial applications is the fact that you have
high minimum pressure requirements for equipment such as coffee makers,
ice makers e.t.c.
To have all stored water above this minimum pressure, you need to increase your precharge on the tank. This increases the backpressure on your membrane right from startup. As the normal unit can only put 60- 70% of line pressure into the tank, you are only able to use a small section of the performance curve of your system.
For example a system that starts at 2 bars precharge on 6 bars feed it would shut down at 4,2 bars tank pressure. On our diagram you would see that you basicly start at 33.3% filling and only use the system to fill the tank up to 70%. The system performance would be between 30- 65% of your rated membrane performance.
With the permeate pump, you run the same unit up to 100% of line pressure and you only see a slight performance drop of 15% at the very end.