The Water Lover's RO system uses the RO product to flush the membranes after every cycle, and in my opinion is completely unneccessary and overcomplicated. All you need is solenoid for supply, pump, solenoid from outlet of membrane(s) to drain for the flush and two flow controls (One to recirculate some of the reject back into the pump, one to the drain or catch tank if the reject is recovered.) When replumbing these, I've always used a JE Adams flow-through high-pressure regulator with about 1/4" of the spring cut off to control the pressure, and simply let the bypass from that be the reject, and use a needle or ball valve for the recirc. It works, it's cheap, reliable, and it's more efficient than flushing with product. I've also found that replumbing a system that has no recirculation of the reject to add that feature will both increases the product from the membrane and reduce the wasted water. If it affects the life of the membrane, it's insignificant.