Sawyer water filters are a small sintered glass filter that attaches to a five gallon bucket. When properly used and maintained, the filer provides 0.1 micron absolute filtration — removing 99.99999% of all bacteria, such as salmonella, cholera and E.coli, removing 99.9999% of all protozoa (such as giardia and cryptosporidium), and removing 100% of microplastics. It will provide five gallons of potable water per day for several years. The bacteria and viruses are to large to pass thru the spaces in the glass filter, therefore the filter must be back-flushed after every use using a large syringe and potable water. Any silt and other solid materials are also trapped in the filter and must be removed by back-flushing. The beauty of this filter is that it requires no power and the water simply trickles out of the bucket through the filter into a clean receptacle.