If you have the space, consider storing 1 gallon of water per person for 14 days. This should be enough for drinking, cooking, and basic washing. Within 14 days of an emergency help SHOULD arrive. Water can be stored in small store-bought water bottles, reused two liter bottles, food grade camping jugs (5-7 gallons), or 55 gallon water barrels. As long as the plastic is food-grade the storing vessel doesn't really matter. You should also consider storing some sort of water filter in case of a longer term or more wide-spread emergency.