A steaming oven having a collector plate disposed in an oven chamber. A collector plate is disposed above a boiling water reservoir in the oven chamber. The collector plate has a drain tube inserted into an overfill tube. Waste material from the steam and food droppings is conveyed from the oven chamber via the drain tube and the overfill tube. A barrier shields one or more water level probes or sensors from water turbulence, thereby providing reliable water level sensing by the water level probes or sensors.