In view of the typical results obtained from pilot plan unit, a trial on the nanofiltration (NF) demonstration unit is not only logical but also essential to determine the conditions of the operations such as feed pressure and permeate TDS. A significant progress is made in understanding the effect of the feed temperature on the nanofiltration performance by using different concentrations of saline water that cover both high salinity brackish water and the seawater range 10K ppm, 20K ppm, 30K ppm and 40K ppm. A complete demonstration unit is constructed in this research applying a NF spiral wound membrane manufactured by Filmtec company type NF90-2540 that shows a high salt rejection. The simulation' runs by the latest simulation software; WAVE by Filmtec company were compared with the experimental results. The permeability percentage of the nano polymer for both monovalent ions such as sodium and chloride ions and the divalent ions such as calcium, magnesium and sulphate ions are discussed in this study as well. It was observed that feed pressure decreased with increasing feed temperature and decreasing feed TDS. Moreover, the salt rejection decreased with increasing feed temperature and feed TDS. The feed pressure results of NF90-2540 proved that the NF power consumption is lower than RO.