Berkey water filter systems come in several different models, all shown on this page for comparison. Each model was engineered with a specific set of guidelines in mind. The most important factor to consider is the number of people that the specific Berkey water filter model would be able to supply drinking water for. A second factor is, how would you be using the filter? Would you be using the water filter system to supply just drinking water or would the water from the Berkey also be needed for hygiene and cooking purposes? Finally would you be using the Berkey system for everyday use or only in emergencies? All models produce the same quality of water (purified). The difference between the models is the amount of water that they are able to produce per hour and the size of the storage container. Larger Berkey models also hold more filter elements, this allows the system to produce water faster because of the higher flow rate.