Laboratory analysis indicates that  Black Berkey purification elements reduce arsenic by up to 99.9% (full test results). All filters that use activated carbon to reduce arsenic begin to lose their efficiency fairly quickly. This is also the case with Black Berkey elements, which lose their arsenic removal efficiency probably well before their estimated service life of 11,300 liters.
A number of filters on the market use charcoal extracted from carbonized bones and claim fluoride reduction, yet fail to inform their customers that the fluoride removal capacity of their filters is rapidly reduced. This is because it takes a very large amount of media to remove small amounts of fluoride. Therefore, these filters do not contain enough media to effectively remove fluoride over the long term. For example, we tested a competitor's three-filter system that uses bone char for fluoride removal. Not surprisingly, these elements deplete quickly. Tests show that their efficiency drops from 100% to 81.4% after filtering only 170 liters, a loss of almost 20% for a use equivalent to less than 60 liters per filter! The efficiency of these filters decreases dramatically. This same effect probably occurs with Black Berkey water filters but only after several hundred liters. Nevertheless, we have developed a more sustainable solution for fluoride reduction by creating  Berkey PF-2 replaceable elements. The media contained in a Berkey PF-2 water filter set can reliably remove fluoride contaminants for up to 3,800 liters, which is less than the life of the 11,300-liter Black Berkey. That's why they were designed to be replaceable. This allows users to reliably remove fluoride contaminants from their water while taking full advantage of the 11,300 liter life of their Black Berkey filters.pleinement de la durée de vie de 11 300 litres de leurs filtres Black Berkey. Black Berkey purification elements are designed to remove a wide variety of potential contaminants. The job of the Berkey PF-2 filters is to remove fluorinated contaminants, which the Black Berkey purification elements can no longer do after extended use.
Keep in mind that actual capacity also depends on the presence of other competing contaminants in the water being filtered. High levels of arsenic and heavy metals, for example, can reduce the capacity and effectiveness of these elements.