I just finished a recording session at a local music studio where they have a Berkey Water Filtration System. The guys at the studio are (somewhat understandably) totally in love with their Berkey, which apparently can be used to filter water from lakes and streams and has been used by the American Red-cross.
Here is a cheezy video from the company explaining Berkey filters.
I think one of these could work pretty well in a tiny house, especially because many of them rely on gravity fed-spigots rather than conventional plumbing. Could be useful for tiny houses used by hermits in the depths of the forest, or helpful for getting off the water grid.
They are pretty elegant too, with their shiny, stainless-steel simplicity.