The paper describes extensions to the EPA-EXTRAN module which can be used for single event or continuous rainfall-runoff simulations as well as for real time control purposes. For surface runoff three different approaches are described. Their use depends on the goal of the simulations - single event or continuous simulation - or the availability of appropriate data (detailed or lumped simulation). The extensions and modifications of the EXTRAN block are reducing stability problems at special structures and make it possible to simulate real-time control devices. The on-line version makes it possible to simulate the behaviour of these devices to test the control strategy for an existing sewer system. The model can be used for training the operators - connected to the control centre and using the available environment - or for testing and further development of the control strategy in a stand alone mode or connected to another PC.