Big Berkey Water Filters is a company that offers a stainless-steel gravity water purification system that removes over 200 contaminants. The system has been tested and shown to greatly reduce or remove most of the contaminants of concern. However, there were issues with the Berkey PF2 fluoride filter elements leaching aluminum oxide into the water, which was almost completely resolved in a second test. The system is large, more expensive, and harder to maintain than pitcher and under-sink filters. It's also worth noting that the manufacturer's performance claims do not have independent certification to national standards. Despite these points, the Big Berkey has a strong following and is praised for its no-install portable design, long filter lifespan of up to 3,000 gallons per filter, and its ability to operate without a waterline connection or electricity. However, the filtered water's taste is reported to be average and didn't impress in blind taste tests. The system is also reported to be bulky and a hassle to set up. Overall, while the Big Berkey Water Filters system has its advantages and disadvantages, it appears to be a legitimate product. However, potential buyers should consider their specific needs and circumstances before making a purchase.