This is a technique conceived and developed in France, which works like the system of isolated drainage wells but overcoming the inconvenience of installing a pump for each well. Once motion is triggered in the siphon tube, without the entry of air into the loop, the flow of water is uninterrupted. For this reason, the two ends of the siphon tube are submerged in the water of two permanent storage tanks. This drain is created vertically starting from the campaign level but can also be sub-vertical or inclined. The diameter of the well can vary from 100 to 300 mm;. Inside a PVC pipe is placed or a perforated or microperforated steel pipe, filled with draining material. The siphon drain in this way carries off drainage water by gravity without the need for drainage pumps or pipes linking the bottom of each well. This system proves to be economically advantageous and relatively simple to set up, but requires a programme of controls and maintenance.