In one sense, storing water for emergency preparedness is simple. It doesn’t need refrigeration. It’s inexpensive. It doesn’t go bad if it is stored for too long. (Although some bottled water does have a ‘best by’ date.)
In another sense, water storage can be problematic. Water is heavy, and you need to store a significant amount. My 90-person-day food supply takes up only about 9 cubic feet (more on that in a subsequent post). 90-person-days of water is 90 gallons. Technically, 90 gallons takes up only 12 cubic feet. But if you store it as one gallon water bottles, there is space around the containers, so it might take up twice as much space if stored on a set of shelves.
So 90 days worth of water takes up much more space, and is much heavier than 90 days worth of food.
The one gallon per person per day rule is found on the FEMA website. But they also state that you can often get by with only half a gallon a day: “you should store at least one gallon of water per person per day. A normally active person needs at least one-half gallon of water daily just for drinking.”
So you might want to consider that 45 gallons is 90-person-days worth of water, at least under ordinary circumstances. FEMA says:
“Additionally, in determining adequate quantities, take the following into account:
* Individual needs vary, depending on age, physical condition, activity, diet, and climate.
* Children, nursing mothers, and ill people need more water.
* Very hot temperatures can double the amount of water needed.
* A medical emergency might require additional water.”
By the way, 90-person-days worth of water (or of food) is enough for 1 person for 90 days, or 2 persons for 45 days, or 3 persons for 30 days, etc. It is easier to keep track of stored food and water in these terms. In an emergency, you want to know how long you can last on stored food and water.
I checked my ordinary water intake recently. I drank only bottled water, and coffee made from bottled water. I measured the day’s worth of water as 1.2 liters, which is just under 1/3 gallon. So if I had to stretch my stored water, each gallon could last three days. But ideally, you want to store 1/2 gallon to 1 gallon per person per day.