Since the filter has pores fine enough to remove viruses, does it get clogged frequently?

The proprietary filter formulation used in Black Berkey™ Purification Elements makes up for the incredibly small pore size by utilizing an exponentially greater number of micro pores in each purification element than that found in other filter elements. This is the reason Black Berkey™ Purification Elements produce approximately 8 times more water per hour than other elements. While some of the surface pores will clog up from contaminates, it is difficult for such contamination to overwhelm all of the pores and thus clog up the filter. Eventually the majority of surface pores may clog up slowing down the flow rate of the Black Berkey™ Purification Elements. When this happens the filter can be refreshed by simply brushing the outside of the element with a ScotchBrite® pad or toothbrush. This will remove the surface pores that have become clogged. Therefore, even though the filters have such small micro fine pores, the element will not clog up prematurely.