Abstract: A closed, cross-flow fluid filter assembly having a pressurized input line for polluted fluids entering into a closed header box. The closed header box fits within a filter tank and is provided with apertures and spacer assemblies on the bottom wall thereof communicating with the filter tank, the apertures providing the pressurized fluid thereto. Filter leaf assemblies are arranged in parallel within the filter tank and are maintained at their top edges in spaced relation by the spacer assemblies. The filter leaf assemblies are composed of abutting offset grids, contained within a fluid tight frame which is covered on each side by a filter media. The filter leafs are drained of filtrate through a medial tube connected to a central manifold which is connected to a vacuum source. Flow-through backwash stop-grids are arranged in the filter tank to prevent excessive bulging of the filter membranes during backwash for cleaning of the filter media.