diatomaceous earth

In conceptual terms, watershape filtration is about as simple as it gets:  Water that picks up insoluble organic materials in the form of dirt, debris, dust and algae is drawn by the pump to pass through a filter medium of one type or another.  The medium - whether sand, a cartridge or diatomaceous earth - traps these materials and lets only clear, clean water back into the vessel. When the pump sends the cleaned water out of the filter, that water returns to the pool to dilute the dirty water in a continuous cycle of cleansing and dilution that ultimately results - when the system is set up the right way - in clear, clean water that's both aesthetically pleasing and safe. Sand, cartridge and diatomaceous earth filters have long dominated the market, and each requires a filter tank with internal components specific to the filter medium it uses.  There are common components (as discussed at the end of this article), but it's important for the watershaper to