#Solar water bag http://cnet.co/NuHTZG
same like solar shower heats up to 50 - 60°C
the perfect temperature to grow bacterias
hiding behind sediment particles in rural water 
main problem in Brazil rooftop water reservoir "caixa".

Gardia, chryptosporidia etc; the concept is to
easy...and who wants to drink 60°C hot water
when he is thirsty ??