Say I have a bag for water, and I fill it with water from a pond and drop a Micropur tablet in there. Well the pond water is inside, but also on the threads and outside. I don't want to purify the water inside only to have my lips touch residual contaminated pond water that was trapped in the bag / bottle threads when I drink it! And I know you're supposed to splash some of the treated water on the threads to address that, but when? In the beginning as the tablet is dissolving? After it's dissolved? I dunno.