Extremely Affordable Gravity-Powered Water Filters     These
filters all use some combination of microfiltration,
disinfection and absorption. Microfiltration simply blocks
bacteria from passing through the filter by using a highly
porous material in which the bacteria bacially get lost.
Disinfection, for example using chlorine, kills bacteria and
other pathogens using chemical means. Absorption, finally, uses
carbon to absorb molecules, improving taste, smell, and color of
the water. Not all filters use all three, and this is where the
main differences in quality lie.  The Siphon filter  So -- 30$,
20$, can we go lower? Enter the siphon filter. Produced by Basic
Water Needs Foundation India, and sold under the brand name
Tulip filter and CrystalPur, it is sold for 10$. To reach that
price point, the filter has been designed in such a way that
only the most essential elements remain: a filter element, a
tube, a tap. That's it.  Siphon3.pngThe ceramic filter element
is made out of diatomaceous earth, a wonderf