The Auto Shut-Off Permeate Pump Valve turns off the RO system's water supply when the tank pressure reaches 90% of the incoming water pressure. It is specially designed for permeate pumps and optimizes their performance in low water pressure situations (less than 40 psi). By using the valve, extra pressure is maintained in the system, boosting the pump output. It connects easily to a 1/4" quick connect fitting.