Abstract: A device for regulating the flow in a drainage siphon tube, includes a rigid tube connected to the outlet end of the siphon tube. The rigid tube is placed on a brace such that it can oscillate around a horizontal axis by means of a counter-weight. Pivoting upward of the tube is limited by a high block stop and pivoting downward is limited by a low block stop in such a way that when the siphon tube is delivering above its critical point, the tube is tilted downward, resting on the lower block stop and when the critical outflow is reached, the tube empties itself and comes to rest against the higher block stop by means of the counterweight. An increase in the pressure at the inflow end of the siphon tube results in a rise of the water in the rigid tube until the imbalance makes it pivot to the downward tilted position where it rests on the low block stop and delivery higher than the critical point ejects the gas bubbles accumulated at the high point of the siphon tube.