The dehydration model provided a suitable chemical tool for prediction of inorganic fouling flux on the RO-membrane. Several important outputs had obtained from these research series that carried out by the present authors during the last five years. Among them, two indicative points are mastering the course, the first belongs to the nature of dissolving salt that are found as hydrated molecules and not as free ions. The second discovery is that the increasing of carbonates and sulfates minerals solubility with the increase of chloride ion (or probably NaCl) in its solution. By estimating the probable dissolving hardness-salt combination and their relative fouling fractions at a given Cl ion concentration it becomes easy to obtain the possible fouling load. Field correlation indicated the proposed guidelines for fouling potential limits. An excel spreadsheet had developed specifically for the RO inorganic fouling assessment (ROIFA-4). which is free for all and available upon request from the authors. The mathematical modeling has been described in detail, and a case study was also presented and discussed to illustrate the capability of this program. The ROIFA software subjected to many laboratory tests and field investigations for more than two years and found to be satisfactory. (C) 2011 Elsevier B.V. All rights reserved.