Deposits build up in sewer networks during both dry-weather and storm-water events. Especially in combined sewers, the sediment materials cause various undesirable effects. Flushing devices are able to remove deposits in sewers by generating flushing waves. To optimize the flushing with so called Storage-Volume-Activated-Devices (SVAD) numerical studies were carried out. The objective was to investigate the behaviour of the activated storage-volume of flushing waves on cleaning performance.