The illustrative embodiments described herein are directed to a manually-actuated pump and method for applying reduced pressure at a tissue site. The manually-actuated pump includes at least one variable volume chamber that is manually compressible into a plurality of positions. The manually-actuated pump includes a fixed volume chamber in communication with the at least one variable volume chamber. The manually-actuated pump also includes a filter housing having a hydrophobic filter that prevents liquid from entering the at least one variable volume chamber. The fixed volume chamber is coupled to the at least one variable volume chamber via the filter housing. The filter housing is located in between the at least one variable volume chamber and the fixed volume chamber. The fixed volume chamber has reduced pressure that is applied to the tissue site in response to a movement of the at least one variable volume chamber from a compressed position in the plurality of positions to an uncompressed position in the plurality of positions.