If you work with a lot of technical equipment you see how failure prone solenoids are. I have replaced them on front loading washers, CO2 systems, RO systems, they are the usual part that breaks in a starter on a car and they have the bad habit of jamming in the open position. In fairness given the thousands of off and on cycles they are pretty reliable but to trust one not to disasterously flood the house- I cannot recommend that level of faith. Also, every time an RO system turns on the water is less pure for about 5 minutes, it will give far purer water if it runs for several minutes to fill up a large reservoir than if it is always off and on as in the off times the normal osmotic process allows contaminant to reenter the pure water. Also, in a large ssystem it may take more than 10 minutes to top up because RO is so slow, the Osmolator will not let any connected device run more than 10 minutes.