text: how do i build a water filer - 2 stage- for 8th grade science class? cant use ready made filters, cant use the same materials in both steps.  must use items i have at home you can try this one:   first stage: use cotton or a t-shirt.   second stage, using coffee filters (or sheets of paper).  if they are not thick enough, then put two or three.  let dirty water flow and you will see how dirt stays in the filter, and clear water comes out  other material that can be useful:  take a little plastic cup, fill it with sand, pack it tight, then make a hole on the bottom.  be careful to let water run slowly, and to pack it really tight