A flange unit for a filter unit for positioning in a water treatment device, the water treatment device including a water reservoir and a suction head. The flange unit includes a base plate having a central recess for accommodating a filling piece of the suction head, a connecting unit for detachably connecting the flange unit to an inner side of the water reservoir, a closure element for closing the recess, and a handle unit for detaching the connecting unit from the flange holding device and for carrying the filter unit.