we're researching the best water filter to have on hand for an emergency situation (i.e., if the power is out for an extended period of time and we need to drink creek water). any suggestions? Especially, does anyone have personal experience with the Berkey water filter? How do I locate objective lab data? Also, I had read years ago that a 'few drops' of bleach in a gallon of water would purify it. True? How much might be too much? Do I need to count drops?