That's right! Silver is used as an anti-microbial so that each Black Berkey® element can self-sterilize. Analysis was performed by an independent laboratory to ensure that the silver used does not dissolve in the purified water and this is exactly the case. The analysis concludes, "All control samples, including stock samples, positive and negative analytical controls, and the negative control collected prior to plating gave appropriate results and were accepted. Results for the leaching control samples (effluent sample spiked with MS2 and R. terrigena and analyzed at two time points) were quite similar, suggesting that no active antimicrobial agents dissolved in the treated water."

You can check the results in this full report.