We have been using a 'sub micron' filter in our under sink fresh water filtration system. The company that made them seems to have gone away and the filters are no longer available. I was ordering a couple more and found a new and even better one. Of course it is at 4 times the price, $50.00

This filter will keep you as protected as if you purchased an expensive 'Seagull' system but uses a standard plastic 10" housing that most people have on their boats.

Filters out all the giardia, cryptosporidium, E.coli and the rest of the bad guys. You can also clean it and reuse it. Fill up anywhere and be safe. (I'd still add a bit of bleach anyway)

Here's the link

http://www.filtersfast.com/Ultra-Carb-Cartridge.pdf