This device allows the operation of the reinforced shaft under an atmospheric pressure which, in certain cases, can reach a value almost zero. The level of loading of the shaft varies according to the contributions and the level of the reservoir. This results in a free-flowing fall that can reach, in the worst case, a nearby difference in level of around 200m. Without special precaution, this fall would funnel very large quantities of air into the pipes and turbines, causing water hammer effects and significant pressure drops. Using a flow under vacuum eliminates these drawbacks. The device is completed by an anti-water hammer shaft and a head valve allowing the siphon and shaft to be kept out of water. In this case, the water flows into the Tour where a structure is provided for this purpose.