Reverse Osmosis (RO) is one of the most efficient methods for salt removal from seawater, saline water and from wastewater. However, efficient application of RO for such purposes is still hindered by several operational drawbacks, the main one being membrane fouling. Herein, field experiments were conducted on a commercial scale membrane system treating domestic wastewater for agriculture irrigation. It was conducted for developing and verifying of a simple and practical tool for evaluating RO membrane fouling. The membrane system consisted of an UltraFiltration (UF) stage and a complementary RO one. The UF component is applied for the removal of the organic matter and pathogenic bacteria while the RO is used for the dissolved solids removal from the wastewater, bringing the water to drinking quality. In our field experiments the membrane system capacity was around 125 m(3)/day and it was run smoothly for a continuous period of four years, providing unrestricted quality effluent that was used for irrigation of a series of seasonal commercial field crops. Following analysis of both field and theoretical data, it was found that back flushing with clean water without adding extra chemicals can be applied in order to minimize fouling of the RO component. Back flushing has two major benefits: saving expenses for the chemicals utilization and improved environmental control. (C) 2016 Published by Elsevier B.V.