A disposable filter cartridge for a pump-filter assembly having a one piece integral pump-filter housing. The filter cartridge includes opposed upper and lower end caps and a tubular skeletal core member open at both ends. A pleated filter medium surrounds the core member and is supported and retained between the opposed end caps. The end caps further include integral flexible gaskets dimensioned to engage pipe fittings of more than one size. A water treatment medium may be deposited within a central portion of the core member. In combination with the skeletal core, a platform means projects radially inwardly from the central core to form a cage-like structure adapted to support a variety of water treatment media. The entire filter cartridge is removable from the housing and may be replaced as desired.