The invention relates to a device 1 for treating a fluid, including a container 2,3 with inner space, at least one entrance to the inner space arranged on the container, wherein the entrance includes a first and second opening 4,5, a grid body 14 which is arranged in the inner space and which divides the inner space into a first compartment for a treatment arrangement, preferably filter material, connected to the first opening 4 and at least one second compartment which is connected by means of a tube 25 to the second opening 5 and which is free of filter material. The tube has a connector arrangement for connecting the second opening to the first compartment.