For my second sink in my kitchen I have a 5 stage filter system. It goes through a UV light to kill living things, then a 3 charcoal filters, one for large particles, another for removing chlorine and the third for removing small particles. Then it does reverse osmosis before heading to the tap. As far as size, it takes up about 1m x 0.5m x 0.5m
Sounds like a solid system, ever tested it to see what difference it makes on a molecular level?
That same amazon page has this for testing http://a.co/dVZweID which I've seen come up a lot when doing research, but it'll only tell you if something is in the water, not what.
I usually skim thesweethome.com for things like this, too.
http://thesweethome.com/reviews/best-under-sink-water-filter... http://thesweethome.com/reviews/best-water-filter-pitcher/#h...
For $15 it will be fun to play with, and roughly compare water sources like my home waer vs X-stage filtered water at Manylabs. No biological test tho, or identification of molecules.
Maybe create an open source dataset and protocol for enabling mapping this data globally?
(Email me if you want updates on my tinkering - tito@impossiblelabs.io)