In a method for cleaning a portable filter assembly including an elongated housing and a mouthpiece assembled with an outlet end port of the housing, the mouthpiece is disassembled from a female threaded portion of the outlet end port. A male threaded end connection of a cleaning fluid source is assembled to the female threaded portion of the outlet end port. A pressurized cleaning fluid is supplied from the cleaning fluid source to the outlet end port and through a filter element disposed in a fluid passage of the housing to expel the cleaning fluid and trapped contaminants from an inlet end port of the housing.