In order to reduce overflow pollution load during rainfall, a real time control strategy has been implemented for the combined sewer network of Saverne (Alsace, France). It consists of optimizing various gate and pump commands over a specified prediction horizon, using graph theory. Flows, trough collectors, weirs and stormwater retention tanks have been represented by a graph and a primal-dual algorithm has been used in order to satisfy rainfall discharge with lower overflow. This strategy has been tested successfully using 685 rainfall events collected over a decade and attractive reductions of both volume and frequency overflows have been observed.