The Zen Water Micro-Ceramic Filter dome made of highly compressed ceramic with diatomic properties. The surface of the dome consists of millions of pores that measure 0.2 to 0.5 micron in diameter, while most bacteria is 0.5 to 1.0 microns in size. The ceramic filter dome sits in the top holding tank. When contaminated dirty tap water passes through the pores in the ceramic filter, it will trap dirt, debris, contaminants and most bacteria before the water passes to the "clean" side of the filter and down into the 5-Stage Mineral Filter Cartridge for further purification and mineralization. The recommended maintenance of the ceramic filter is at least once a month, or as often as necessary, depending on the quality of water. Over time, the trapped dirt and contaminants will begin to buildup, forming a layer of gunk on the surface of the ceramic filter. Scrubbing the surface of the ceramic dome with a scouring pad or soft brush under cool running water will unclog the pores on ceramic and expose a new layer for use. The expected useful life of the ceramic filter is 1,000 gallons or 1 year, whichever comes first. The normal flow rate is approximately 1-1/2 to 2 hrs. for every gallon. When the ceramic is in use for the first time, the flow rate might be slow, but it should speed up in a few days. The Zen Water Micro-Ceramic Filter dome is designed and guaranteed to fit universally across all Zen Water models. The ceramic filter dome should be handled with care. Do not use the ceramic filter if it is cracked or damaged.