How much water should I store?

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.

More reading: Water Basics Emergency Disinfection of Drinking Water
FEMA Guidelines for Managing Water Supplies

– Thoreau

4 Responses to How much water should I store?

  1. When storing water you should have enough for at least a week just due to the space. You should also include other ways of obtaining water. A berkey water filter is great for the house. You should also have one in at least your camping back pack.

    Rain water collection is also very useful.

  2. Thoreau:

    A couple of thought. First, I would argue that your closing thoughts on a 1/2 gallon per person per day (pppd) will turn out to be light, notwithstanding your daily experiment. In my opinion, and based on a bit of camping, etc., the gallon pppd is more in tune with TOTAL water usage, not just drinking. Keep in mind, there are other uses of water other than drinking such as cooking, cleaning, personal hygiene, and clothes washing. Even in a SHTF scenario, you will still need water for these purposes, though you can be more sparing in its uses. Cooking alone can use a half liter to a liter pppd if you are using rice, beans, pasta, freeze dried or dehydrated food. Also, any sort of physical exertion, almost a certainty in a survival situation, will make one thirstier than normal.

    Second, be mindful of how one stores water. If storing store-bought bottles/jugs, avoid the cheap 1-gallon jugs with the translucent but not transparent plastic. That plastic is not designed for long-term storage and will start to breakdown, especially if placed on a concrete floor. While I have not stored such bottles, others have suggested they start to leak after about a year, less in less than ideal conditions. In my mind, the best store-bought containers are the clear plastic bottles which are very stable and available in all manner of sizes. In our basement, we store 3-liter Poland Spring bottles and use a rough “bottle per person per day” formula (a gallon is approximately 3.8 liters). Stored in a cool, dark, dry space, I have read that these bottles should keep water drinkable for years. However, at $1-1.50 per 3-liters at a typical market, these are not cheap. The better alternative is catching a super sale where you can by a case of 24 liter bottles for $3-$6. Much cheaper though, as you point out, will require a bit more storage space.

    Lastly, in addition to having 65 of the 3-liter bottles stored on racks, we also have bought two water filters. We have a pool in our backyard, a creek nearby feeding into a reservoir. Thus, we can augment the bottled water with filtered water from the “wild”. The two filters we have are a middle-of-the-line camping filter with a pump and a “camp” filter. The camp filter is a large fillable vinyl bag which feeds into a filtering unit and works on gravity. Slow but effective for large stationary usage. The pump filter is more for on the go and is kept with the gear we might need it we ever had to leave the house.

    I hope this proves helpful.


  3. I noted your Katadyn ad so figured I would point out the camp filter that I have:

    Sorry about the long url. If that does not work, try this:

  4. This question tends to come up a lot, and few actually count the quite prodigious amount of water they already have on hand. You have a full hot water tank (anywhere between 20 and 50 gallons), a bathtub that can be filled up (even better, get a Water Bob – it’ll keep that water clean), which gives you about 30-50 gallons more (typical suburban tub size – you get that 50-gallon total by plugging the overflow vent and/or using a Water Bob). Your toilet tanks hold 5 gallons apiece (sometimes less for the high-efficiency models).

    In all, a sharp prepper with a 50 gallon hot water tank in a typical 3bd/1.5ba home should be able to rack up 110 gallons of potable water in less than 20 minutes… not counting the 5 gallons or more resting inside the house plumbing in that house. You turn off the hot water tank and toilet water valves, fill the tub (with or without the water bob – either way that is what will take the longest time to do), and you’re good for a supply that can stretch (if needed) up to 220 person-days of potable water (1/2 gallon per day consumption). If you have two full baths, then you bring the total up to 160 gallons, or up to 320 person-days of potable water. That’s enough to keep two people hydrated for just under six months.

    (…and we haven’t even counted the sinks, though you fill those up for washing water, since kitchen sinks contain a lot of germs, and bath sinks will be needed for washing. Other impromptu water storage bits include the washing machine, trash cans, those plastic storage tubs, etc.)

    Add in a decent backpacker’s water filter or two, and you have the potential for a whole lot more if there is a river or stream nearby (hat tip to Nate, who bought up the need for a continuing supply of water).

    Overall, a decent stack of potable water is fairly easy to come by in most places if you’re quick and sharp. I guess what I’m saying is that the only place you really need to worry as much about water is in more arid regions.

    Now if you live in an arid region (rainfall less than 20 inches per year avg.), then water preps had better be at the very top of your list – higher than food. In such places, it pays to build and keep a full cistern in the basement… 1,000 gallons would be a good start, because in arid regions you will be burning through a gallon per person, per day – if not more during the summer.