The operation of the AquaRain® Natural Water Filter is simplicity itself. No energy is required nor are chemicals necessary for the filter system to work. Water is poured into the upper container where it trickles down by gravity through the highly specialized ceramic filter elements leaving cysts, bacteria and ultra fine sediment in the outer layer of the ceramic. After passing through the thick ceramic wall, the water then flows through a bed of silvered coconut shell carbon which adsorbs pesticides, various organic chemicals, and chlorine (if present), along with objectionable color, tastes and odors. The filtered water then drips into the lower container where it is stored for easy dispensing with the handy lever-action faucet. Over time, small particulates and bacteria may accumulate on the walls of the elements and slow the production of water through the filter. When this occurs, simply remove each of the filter elements and lightly clean the hard surface of the ceramic with a brush or the scrub pad provided. (Unique end-of-life gauges takes out the guesswork from knowing when to replace the elements.) The elements are then reinstalled in the upper filter vessel. Proper cleaning will restore the AquaRain® Natural Water Filter to full flow rates, each and every time. Model 200: This is our smaller version which can use up to two high performance cartridges mounted into a 1½ gallon stainless steel housing and incorporates the same features as our larger unit. When kept full, you can expect this unit to produce a maximum of ½ gallon of clean and great tasting water an hour. The Model 200 stands 18 inches tall overall and is about 8 inches in diameter. This unit comes with one filter and can use up to two filters.