<p>A method for retrieving excess pharmaceutical process fluid from the hold-up volume of a primary fluid filtration device. The hold-up volume is the volume of excess process fluid which accumulates in the bottom of the filter housing below the outlet opening thereof. Because it is considered valuable, the excess pharmaceutical process fluid is retrieved from the lower housing (22) via a drainage port (23) formed therein below the level of the outlet. The excess process fluid is then filtered in a supplemental filtration device (100) that is connected to the drainage port. The supplemental filtration device has a smaller volumetric capacity than the capacity of the primary fluid filtration device.</p>
