This element is made by rolling membranes into a spiral, they are usually 40 or 60 inches long, and the most common diameters are 4 or 8 inches. During operation, the water enters under pressure from one side of the housing, as it flows tangentially to the membrane, part of it passes through the membrane surface towards the permeate collector, while water with a high concentration of salts exit at the other end of the membrane.

Reverse osmosis is a membrane technology that allows the removal of salinity from water. It is based on a diffusion process through a semi-permeable membrane that facilitates the passage of dissolved gases and low molecular weight molecules without an electrostatic charge.