An on-demand filter structure including a first hydrophilic protective layer comprising a first surface exposable to a stream of water. A contact area on the first surface receives the stream. The first hydrophilic protective layer receives the stream and distributes water out a second surface, primarily using gravity. An activated carbon felt (ACF) layer is adjacent to the second surface, wherein the ACF layer is configured for water filtration, primarily using gravity. A second hydrophilic protective layer includes a third surface adjacent the ACF layer and a fourth surface. The third surface receives filtered water from the ACF layer, and the fourth surface expels the filtered water primarily using gravity, wherein the first and second hydrophilic protective layers sandwich the ACF layer. A cross section of the first hydrophilic protective layer, the ACF layer, and the second hydrophilic protective layer has a curvature.