A study was carried out on a NaCl H2O RO thin film composite reverse osmosis membrane system to characterize these membranes, determine their performance and predict the effects of pressure and solute concentration in the feed using the correlation from the Kimura Sourirajan analysis. The effect of the solute concentration in the feed (0.0043-0.086 molal) operating at pressures of 500-2000 kPa was studied. The permeability constant, A, and the transport parameter D-Am/k delta for CA 990 PP and HR 98 PP flat membranes were calculated and the results from both membranes were compared. The M20 lab unit had a total permeation surface of 0.72 m(2) when all 20 membrane pairs were installed. During the experiments one pair of membranes was installed, resulting in a permeation surface of 0.036 m(2).