a water treatment apparatus includes a housing comprising multiple housing portions and a plurality of treatment sections disposed within the housing , each treatment section comprising at least one distinct particulate layer . the apparatus is designed so that no water pressure need be applied to force the water through the apparatus , as gravity pulls the water down through the filtering layers . water may also be force fed through the treatment apparatus ; when the water is force fed , the housing portions need not be vertically stacked , but may be configured in any suitable arrangement . the treatment sections are distributed through the various housing portions in logical groups to perform various kinds of filtering . the housing portions are detachable and sealably stackable in multiple configurations , thus passing water through more or fewer treatment layers , depending on the quality of the incoming water .