A device and method for handling waste water to-be-discharged out of a dishwashing machine that includes a pump well and a sump section, with the sump section communicating with the pump well in the lower regions of the dishwashing machine through an inflow section. The device also contains a valve located in or operating with the inflow section that blocks the influx of waste water from the pump well into the sump section when the valve is closed. The valve allows the influx of waste water from the pump well into the sump section when the valve is opened.