Hi all,

Please comment, correct, and update this thread.  It is meant to be a work in/for progress.

Thought I'd start a thread with info on drinking rainwater. 

one of the highest quality water sources out there. much better than groundwater if collected and stored properly. 

upwind contaminant sources: not collected directly downwind from industrial pollution sources...it's not the rain, it's the air that is contaminated...we're breathing this anyway... 
clean surface: metal, slate, bamboo, glass are preferred, can also use clay...other catchment materials? 
contaminant exclusion: First flush filters and screens http://en.wikipedia.org/wiki/First_flush_device http://rainharvesting.com.au/products/pre-filtration/first-flush-water-diverter http://www.eco-web.com/edi/02431.html also, clean gutters via maintenance or leaf screens are beneficial 
non-leaching tank with biofilm: Non-leaching tanks include Polyethylene, ferrocement, stone (of certain types), metal (usually aluminum or galvanized steel) A major portion of non-leaching is the development of a biofilm usually including algae, this means the inside of the tank needs some access to sunlight to grow photosynthetic algae 
screened openings: prevent rodents and insects from getting into the system 
elevated outlet pipe: needs to be 3" minimum above bottom of tank to avoid disturbing the settled sediment and biofilm 
pH management: pH needs to be above 6.0, ideally 7-8. use limestone or marble chips since rainwater is naturally about 5-6. keeping the pH above 5.5 ensures heavy metals are not dissolved. above 8 insures few, if any pathogenic bacteria can grow. 
I need to find some more detailed references on this, but for now http://www.who.int/water_sanitation_health/dwq/gdwq3rev/en/ 
overflow/airvent: can be the same or two different components: screened. 

Some of my favorite resources on rainwater collection and drinking using tanks 

OAEC Water Institute: http://www.oaecwater.org/publications 

review of a decade of rainwater harvesting research: http://www.hydropolis.com.au/Papers/SIA_Coombes1.pdf Awesome! includes info and data on the "treatment train effect" 

Brad Lancaster's books and website are great resources as well
http://www.harvestingrainwater.com/

as in my ferrocement thread, this is lacking some cold climate context details