Storing water:
Store some drinking water in bottles in a dark place. (Under bed, bottom of wardrobe, under stairs etc)
Store water purification tablets. (Cheap and small)
Know how to purify water (filtering and boiling,
Evaporation and condensation)
Have the means to boil water. (Camp stove, Kelly kettle etc)
Have a means of collecting rain water. (Fresh and stored if space)
Keep a reasonable amount of the drinks you usually drink and use on rotation. (Pop, fruit juice, soya milk etc)
This is how I store water.