All Berkey Water Filter systems are classified as high performance water filters. In order to meet these standards, a water filter must be able to address specific contaminants to a predetermined level, known as a "standard". This standard is the highest level of water contamination removal that a water filter can obtain and very few manufacturers are able to make this claim without the use of harsh chemicals like iodine or chlorine. Berkey Water Filter Systems, such as the Big Berkey, does not use chemicals. Instead, we rely on simple time-tested micro-filtration and a unique ionic absorption technology to filter the water.