A reduced pressure treatment system includes a liquid-collection canister for collecting liquid from a tissue site to which reduced pressure treatment is applied. The canister includes a first space configured to collect the liquid from the tissue site and a filter having a frame and a non-planar filter element. The filter defines a second space within the canister separated from the first space by the filter element. The filter element substantially prevents liquid from passing from the first space into the second space. The filter element substantially allows gaseous communication between the first space and the second space when the second space is exposed to a reduced pressure.