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To facilitate the flow of product water within the membrane bag, a fabric support layer that guides the flow of the product water is inserted inside the envelope-shaped membrane bag; to ensure uniform flow of the water over the surface of the membrane bag and to create turbulence in the water flow, a mesh layer is placed in the water supply channel between the membrane bags. The three sides of the membrane pocket are bonded together with adhesive; if the pressure on the water side of the product is higher than that on the feed water side, these bonding lines will break, resulting in a loss or significant reduction in the desalination efficiency of the membrane element. Therefore, for safety reasons, reverse osmosis systems must not have backpressure. Since reverse osmosis membrane filtration is driven by pressure, there is no backpressure during normal operation. However, if the system is operating normally or has stopped due to a fault, and the valves are not set or operated properly, backpressure may occur; therefore, it is necessary to address this issue of backpressure properly. The importance of having an automatic flushing function in industrial ultrapure water systems: After the feed water enters an industrial ultrapure water system, it is divided into two streams. One stream passes through the surface of the reverse osmosis membrane to become product water, while the other stream moves parallel to the surface of the reverse osmosis membrane and becomes increasingly concentrated. This concentrated water contains a large amount of salts, as well as organic substances, colloids, microorganisms, bacteria, and viruses. When the reverse osmosis system is operating normally, the feed/wastewater flows along the surface of the reverse osmosis membrane at a certain flow rate; as a result, it is difficult for these contaminants to deposit there. However, if the reverse osmosis system stops operating, these contaminants immediately deposit on the surface of the membrane, causing contamination of the membrane elements. Therefore, an automatic flushing system must be installed in the reverse osmosis system, using clean water to flush the surface of the membrane elements during shutdown periods, in order to prevent the accumulation of these contaminants.