Keeps wastewater from the sewage system back outside the building in the event of backwater. A revolutionary feature is the standard option of installing the KESSEL backwater valves Staufix SWA, Staufix FKA and the backwater pump Pumpfix F - and this can even be done many years later. This means backwater protection features are located outside the building, functional reliable and easy to service. This combines safety with space-saving.