The offical statement:

Water Pretreatment
  • Water from a chlorinated municipal water supply does not need further treatment when stored in clean, food-grade containers.
  • Non-chlorinated water should be treated with bleach. Add 1/8 of a teaspoon (8 drops) of liquid household chlorine bleach (5 to 6% sodium hypochlorite) for every gallon (4 liters) of water. Only household bleach without thickeners, scents, or additives should be used.
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