That's correct! Silver is used as an antimicrobial agent allowing each Black Berkey® element to self-sterilize. Analysis were conducted by an independent laboratory to guarantee that the silver used does not dissolve into the purified water, and this is precisely the case. The analysis concluded: "All control samples, including stock samples, positive and negative analytical controls, and the begative control collected prior to seeding yeilded appropriate results and were accepted. The results of the leaching control samples (effluent sample spiked with MS2 and R.nterrigena and analyzed at two time points) were quite similar, suggesting that no active antimicrobial agent is leaching into the treated water." 

You can view the complete report results (in English).