Theron, I have two 5hp high pressure pumps. I can tell you that the difference between one pump and two with two membraines is huge. two membraines is too much surface area for one pump to work efficently. When one of my pumps was broken I could only get the pressure up to 250psi. Reverse Osmosise is a function of pressure across a semi permiable membraine. Without obtaining the optimum pressure you will not acheive efficent performance.