The "1 gallon per person per day" water storage rule doesn’t always factor in your household’s specific needs. So I built a free calculator that does.
Posted by Signal_Brain_933@reddit | preppers | View on Reddit | 115 comments
Hey all; flight attendant, dad, long-term casual prepper here. Wanted to talk shop about emergency water storage.
So I’m always seeing the preparedness tip “1 gallon per day per person” everywhere; it’s pretty much on every ‘standard’ emergency checklist, most YouTube prep videos bring it up (except for those made by people who actually bother to think through complex readiness situations), not to mention every FEMA handout. But it just didn’t sit right with me, like it seemed that this advice was mostly designed as the bare minimum for an average, minimally active adult in temperate conditions. 1 gallon per day per person doesn’t factor in cooking, pets, and no real sanitation needs beyond drinking. That’s not practical reality for most emergencies (short or long term scenarios), and I feel like the generic advice might be doing a disservice to people who want to be prepared for a variety of scenarios.
A family dealing with hot summers and cold winters with kids and a dog (my exact family situation) is in a completely non-generic situation. Example: in winter our bodies need more water than you think just to stay warm and hydrated indoors. And in the summer the “needs gap” gets even wider. The 1g/day rule wasn't “technically” wrong when it was first written by some bureaucrat somewhere (it’s an easy figure to remember for everyday families who don’t want to think too hard about this), but I don’t think it actually works very well for most of us.
For my own household (two adults, two kids (11 and 15), one large dog, cold winters and hot summers), the real number (based on my own calculations) came out to 20.4 liters / 5.4 gallons per day. For a 2-week supply that's 285 liters / 75.4 gallons total.
I got my numbers by building an HTML calculator that works through a person or family’s actual situation. You put in your household size and ages, climate, pets, activity level, and whether you'd be cooking with dry goods in an emergency situation. It breaks down exactly where your water goes; drinking, sanitation, cooking, pets - so you can see what's influencing your results instead of just a final total. It also tells you what that amount of water looks like in real containers (jerry cans, jugs) so you can actually go buy the right sized containers (or swimming pool, if that’s how you’re playing it).
Free, works offline (so long as you’ve pre-loaded the page in into your browser first), you can print your results, no account needed: https://omniprepper.com/free/water-calculator/
Curious what numbers everybody else gets, especially anyone in more extreme climates or with larger families, or livestock, etc. If the methodology looks off anywhere, or if other variables should be included, please say so, I’m happy to keep improving this tool. And if my methodology is off anywhere, please let me know. I’d rather fix it than defend it.
BelleMakaiHawaii@reddit
Our household goes through 175 gallons of water a week (two humans, three dogs)
Seven-One-Three@reddit
I was always under the assumption that the one gallon a day per adult was for drinking water only. It didn't factor in cooking, cleaning, etc. It was at the minimum how much water an adult would need to drink a day.
DerLyndis@reddit
Correct.
Adorable_Dust3799@reddit
I can't imagine drinking a gallon a day 😫. More likely potable water. You can shower and flush with city rainwater but not brush your teeth. You can wash dishes with city rainwater but a final rinse of eating surfaces should be with potable.
Signal_Brain_933@reddit (OP)
Yeah, I always keep in mind how many people died of dysentry before water sanitation was standardized. I travel a lot for work to other countries (India, South America) and always carry a Grayl water purifier bottle with me just in case.
Adorable_Dust3799@reddit
I'm in a more arid area and in a long term water emergency people will be camping near available water. That'll get scarey fast. The surfers started tracking ocean water quality long ago when they realized that surfing after storms = sinus infections. Rainwater washing waste down the gullies into the ocean. Dog poop is a lot of that. Along the border the water is tainted from overwhelmed facilities in Mexico.
Signal_Brain_933@reddit (OP)
Wow; see that's a variable that's easy to forget about in an emergency, when you're focused on your own situation. Dog poop? That wasn't on my radar at all.
MerelyMortalModeling@reddit
Medical person here, surfer sinusitis comes from the normal biotia living in ocean muck. Storm swell stir up all the crude and critters living there.
That said, storms wash everything into the ocean, all the poop from everything, dead carcasses, industrial waste, ground molds, sewage overflow, everything.
Also, you haven't lived until you help pull a bloodworm out of the nose of a freaking out teen who decided to ignore storm surge warning and try to surf.
Adorable_Dust3799@reddit
The Tijuana river runoff is epic and absolutely unbelievable for people who haven't experienced it
Signal_Brain_933@reddit (OP)
Ooh, man, wish I'd read your comment after lunch, not before! 😉
Adorable_Dust3799@reddit
No, it was a bit of a surprise to everyone, as the homeless weren't as big of an issue back then. San Diego is crisscrossed with undeveloped canyon areas and they didn't press pick up after your dog as much, as it was thought to just decompose. This was like back in the 70s and 80s, so not recent, but definitely relevant. We actually had a hep a outbreak about 10-15 years ago from homeless. I wouldn't touch open water in a shtf situation anywhere except maybe Michigan
Signal_Brain_933@reddit (OP)
Yeah - I hike a lot and never trust water no matter how clear it is, so I always have a portable filter with me no matter how short or long the hike. And I keep filtration options at home also. Even when I'm on snowshoe treks and have to melt snow for drinking water, unless I'm boiling the water beforehand, I'll filter the melted snow just to be safe.
MagnoliaProse@reddit
A gallon isn’t that out of scope. I’m 5’4, petite, and I drink at least a gallon on an average day. If I’m actually working out or in the garden, I drink a lot more. Some of that is through herbal tea, but that still counts.
jmar289@reddit
When I'm working outside in the heat I can easily drink more than a gallon of water in a day. I usually have a 32oz insulated cup and a 64oz insulated bottle that I bring with me to jobs and I'll finish those before I get home. Plus at least two 16oz glasses of water in the morning and 3-4 more after getting home.
Adorable_Dust3799@reddit
I'm on the other extreme, a 20 oz coffee, and 32 oz water and unless i work at that's it. On a good day another 20 oz. On a bad day i drink my coffee and forget to have anything else. Always figured I'll die of kidney failure, but so far the numbers are good
MistyMtn421@reddit
We get a lot of water from our food too. Plus it really depends on your body and activity level.
I have low BP, I'm short and live where the climate is pretty mid except January and August. By the time I've hit 32oz water I am already peeing clear.
Hot days, strenuous activity days or low appetite days are different, sure.
Delgra@reddit
this is the thing many “preppers” fail to recognize. In a grid down situation or a natural disaster you aren’t just sitting at home playing video games. You are likely out busting your hump clearing and fixing things for yourself snd hopefully your community and neighbors. When normal stops, you are going to be engaged in much more manual labor. This increases water needs as well as caloric requirements.
NotAnotherRedditAcc2@reddit
The rule of thumb I always have heard is 2 gallons per person, per day to cover basic cooking/bathing/laundry needs.
Fragrant-Platform163@reddit
It's usually calculated as 1/2 gal per person per day for drinking, and 1/2 gal per person per day for cooking and hygiene. But they do say to err on more because some people drink more. Safe to say, bathing and such would be limited to a washcloth wipe down. Dry shampoo for hair.
I could not drink a full gallon in a day, even working out and sweating profusely in the heat. Outdoor job. It helps to fill a measurable container and drink naturally, then at the end of the day think "how many times did I refill it?". I've measured it before and it came out to 2L, maybe a little over, which is .5gal. So 1/2 gal is about right for me on an average day. If you're 6'8" obviously you're probably going to need that full gallon. One guy I work with probably goes through that sitting in an air conditioned office, but he also eats a ton of high sodium high protein foods, which increase your water intake. If you plan to eat heavily preserved, high sodium (canned goods) processed foods (or MREs god help you), go ahead and double that number.
For pets it's generally 1/2 gal per pet per day, but my cat is more like 1/4 gal. and my dog is more like 1 gal so you just have to measure do math. Assume it will be hotter than it currently is.
MerelyMortalModeling@reddit
Drinking and cooking. As you mentioned though it's just an easy round number to base estimates on.
Signal_Brain_933@reddit (OP)
Agreed, but that was part of my issue with the number. Most people might not think beyond that simple equation for water storage, forgetting that they still need to account for pets, hygiene, and food prep.
Financial_Resort6631@reddit
Not to get political this is just a fact. Right now People in Gaza are living off of a gallon per person per day. It the emergency levels. To keep you alive.
Sleddoggamer@reddit
I thought everyone knew its half a gallon for drinking, then half a gallon for cooking and other essential use.
You need to factor in other needs, which sometimes allows greywater usage you can pull from none standard storage
No_Staff594@reddit
In the army the standard is 7 gallons per person per day because personal hygiene is important in rough scenarios to maintain your numbers and general health as a group/unit. I’d say 1 gallon per day wouldn’t be nearly enough for long term survival because on a hot day you’re drinking 2/3 to nearly all of that leaving nothing clean in your rations to be used for bathing, brushing teeth, cleaning dishes, or even just maintaining and washing clothes by hand if need be. 7 can be a stretch because obviously for a family of 5 you’d need almost 200 gallons of clean water just to live for one week but it’s something to strive toward. Obviously a shower every single day is nice but not necessary in survival. Yes cleaning your dishes actually matters. And YES clean your clothes from time to time for your own sake and to allow the clothing to last longer
beached89@reddit
It is a rule of thumb. A rule that, if followed, you will not die and your basic needs will be met enough until the emergency is over.
It isnt supposed to be ideally perfect number.
By your own math, your family uses only 0.4 gals/day over the rule of thumb. Proving that it is pretty darn good for you.
MOST people need a simplified rule of thumb, not a math formula they have to constantly go re-look up and double check. 1gal/person/day is an easy to remember rule of thumb.
Signal_Brain_933@reddit (OP)
Totally fair point, and I don't disagree that simple rules of thumb have real value (I work in aviation, we have like a million easy to remember rules of thumb to cover all types of emergency scenarios) especially for people who are just starting to think about preparedness. Easy to remember rules beats technically perfect if it actually gets people to act. The 0.4 gallon gap per person per day is real though, and over two weeks for a family it adds up to about 40 liters unaccounted for. That might be fine depending on your own situation. For someone with livestock, young kids, or a hot (or cold) climate it starts to matter way more. The calculator isn't meant to replace the rule of thumb, it's mostly meant for people who want to know their specific number once, store it somewhere or remember it (if they have a better memory than I do), and not have to think about it again. Run it once, know your target, done. Probably the same kind of person who'd rather have an exact shopping list than a rough estimate (again, like me).
Wolfe_Shepherd@reddit
Following the 1 gallon per person per day rule (yes, counting your dog) would put you at 5 gallons total per day. So it's not a 0.4 gallon gap per person per day. It's just a 0.4 gallon gap per day total.
0.4 gallons x 14 days = a 5.6 gallon shortage
Tools like this aren't a bad thing to have. It never hurts to do specific calculations. I think a lot of the pushback you're getting is because the end result of your calculation is still pretty close to 1 gallon per person per day. It's a perfectly fine rule of thumb and your post makes it seem like you think it's terrible and stupid.
Signal_Brain_933@reddit (OP)
That's the right way to frame the math and I probably should have been clearer about it in some of my replies. 0.4 gallons per day total, not per person. The 5.6 gallon shortfall over two weeks is real (and being a numbers guy, a red flag for me) but not the end of the world for a household that's otherwise well set up. And you've identified the issue with my post title better than I have. I don't actually think the 1 gallon rule is terrible, tbh; I think it's a fair starting point that most people probably treat as a finish line. That's the gap I was trying to address with this little project, and the framing probably got in the way of that message for some people. Lesson learned for the next version.
Wolfe_Shepherd@reddit
I think it's a good conversation to have. Also, reddit wouldn't exist if we didn't have these nuanced conversations. But yea, I think it just came across as unnecessarily specific to some people? But good on you for making this tool. Seems like a lot of people are finding it useful!
Signal_Brain_933@reddit (OP)
Thanks, I hope so! I’m happy for all the feedback as it’ll help me update the calculator and hopefully make it even better and more versatile based on all the comments received here!
dittybopper_05H@reddit
Yes, it includes cooking. It's only a problem if you throw out the water you used to cook something like pasta. So make noodle soup, not spaghetti. Just talking about ingesting, I doubt I ingest a gallon of water in food and liquid form (including other drinks) except on the hottest days of the summer when I'm working hard outside. And much of the food I would ingest would already be hydrated: Canned foods and foods in retort pouches don't need added water generally, or if they do (like condensed soup), it's fairly minimal.
Per person doesn't include pets, because pets aren't people. At least, that's not been allowed in the US since 1863. You have to plan for pets separately.
Sanitation can be achieved with very little water. One of the things we do because clean water is cheap and plentiful is that we use it profligately for things like cleaning. We often over-use it, and could very well restrict how much we use to a bare minimum. Baby wipes are friggin' awesome. They are great for personal hygiene, and good for all manner of cleaning chores. We discovered this when the littlebopper was an infant. He's in his 20's now and lives a thousand miles away, and we still buy baby wipes. They have 1,001 uses.
Now, they're not as refreshing as a shower, but certainly adequate to avoid the issues that come from not cleaning your stanky ass. They are way better than toilet paper in a "shit hits the can" kind of scenario.
Also, if you use disposable cups, plates, and flatware, really all you need to wash is your actual cooking vessels, and that isn't as much water as you might think.
A gallon a day is perfectly adequate, outside of perhaps the desert southwest. So yeah, you'll need more in Death Valley. But up in the Northeast? Midwest? South? Pacific Northwest? Probably not.
Signal_Brain_933@reddit (OP)
Hard to argue with most of this, honestly. Baby wipes are genuinely underrated, big time. As a backpacker they’re my go-to backcountry shower and they work. The disposable dishes point is smart too.
Where the calculator tries to do better than the flat rule is exactly what you’re describing, the food prep variable (simplified for likely emergency food prep) changes the number depending on what you’re actually cooking. Ready-to-eat and canned foods land at one number; dry goods like rice, pasta, and beans at another; dehydrated and freeze-dried meals at another.
Someone living on retort pouches needs significantly less cooking water than someone boiling rice every day. The 1 gallon rule can’t capture that distinction, but this tool can.
And your climate point is fair for most of the continental US in mild conditions. Where it’s less applicable is households that don’t fit the “baseline”, kids, pets, chronic illness, physical labor during the event, or genuinely hot summers. For a solo healthy adult in the northeast sheltering in place, yeah, 1 gallon probably holds up fine. That person was never really the target.
IamNana71@reddit
One thing that needs to be considered is that over hydration is a thing, and it can be deadly. If your slugging down water in an emergency situation, and your dietary standards have changed, you run the risk of over hydrating and potentially flushing sodium out of your system.
Just something to consider. Hyponatremia isn't something you want to deal with in a situation where medical help isn't readily available.
I deal with chronic hyponatremia and I can tell when my sodium is low, but it is something I have been dealing with for a few years. Others can misread the signs and assume they are dehydrated and actually make their situation worse.
Signal_Brain_933@reddit (OP)
Great point! That's a challenge for sure; how do you keep track of this? Are there specialized tools to measure your sodiu like diabetics can measure their blood sugar levels?
IamNana71@reddit
No. Most people associate cramping with being dehydrated however cramping is my first sign on my sodium being low. Also, urine color can be an indicator. I always thought light was great, but apparently clear or nearly clear is not so great. I was told to always keep an eye on the color also.
Seriously though, during my weightloss journey, I spent alot of time in forums with people downing a gallon of water a day or more and many of them complaining of cramping. All the comments were you need more! I was the only person saying stop!!! Go ask doc to check sodium!! It is easy to overhydrate and the symptoms can be similar to dehydration. Muscle cramps, nausea, headaches. If there is ever any doubt, add some salts yo your water!!! That way you are still getting hydration, but your not flushing the sodium out of your body.
Signal_Brain_933@reddit (OP)
There are so many personal drinking water tracker/motivation health apps out there now, I wonder if any of them factor in electrolytes and special medical situations like this.
IamNana71@reddit
I don't know, it isn't something I would use. Would be interesting to know though.
It sucks having this though. I prefer ice cold plain water and that is pretty much off the table these days. Drinking salt water gets old fast!
BigSeaworthiness1467@reddit
The prepper channels I watch all say 2 gal per person per day. Canadian Prepper, Provident Prepper, Angry Prepper, City Prepper, etc
Signal_Brain_933@reddit (OP)
That’s a fair correction and honestly better sourcing than I gave credit for. I was thinking of the more mainstream preparedness content that leans on the FEMA figure, but you’re right that serious prepper channels have been recommending 2 gallons for a while. If anything that makes the calculator’s output look conservative rather than alarmist… for example my household at 5.4 gallons a day is well under the 2 gallon per person baseline some of those channels suggest. Good channels to reference for anyone who wants to go deeper on this.
BigSeaworthiness1467@reddit
I think it's great that we are prepping with any amount of water! I feel so lonely at times because everyone around me (including my spouse) will not prep at all! I keep telling friends and family to prep for at least 2 weeks of water and food but they think I am crazy. 1 gal per person is great and fantastic! I wish I had friends and family like people in this thread!
Signal_Brain_933@reddit (OP)
Same - I’m really the only person in my friend group and extended family that believes in preparedness. It does get a little lonely at times.
Old-Mycologist4750@reddit
Question…. Is there a way to set it up for multi variables of animals? Say 2 lg dogs, 4 cat, 6 chickens, or whatever contingent of animals you have at your homestead? I know it would be onerous to have a single box for each possible animal and/or number of that animal, but is there any way someone could preload those particulars for their own situation to figure it out? (i.e. ability to input # of animals by size and/or species and their water requirements for a given day?) Because like you were expressing, a lot of people under estimate the amount of water that is needed for everything in the household (household to include livestock or whatever you are responsible for in this case).
*BTW, this is AWESOME! I am not knocking it in the slightest. I just know that some people (us included) have multiples of animals and those animals need to be accurately accounted for in order to prep for them properly as well. I have accounted for people and household pets fairly accurately it seems but have probably underestimated other animals when considering other factors.
Signal_Brain_933@reddit (OP)
This is exactly the kind of feedback I needed, so thank you!! Right now the tool lumps pets into size categories which works okay for a single dog or cat but completely breaks down once you have a mixed household. I have a Sheepadoodle and a really cute yellow leopard gecko myself, and we've had cats, tortoises, iguanas over the years, so I definitely know that "2 large pets" doesn't capture that at all, let alone anyone with chickens, goats, or horses.
V2 will have a proper multi-animal input, species or category, quantity, and size, so you can build out your actual animal situation rather than forcing everything into a rough approximation. Livestock included. I'll make sure it handles the kind of situation you're describing.
Adding this to the V2 list now. Really appreciate you taking the time! Have a great Sunday evening!
Old-Mycologist4750@reddit
Thanks for responding to my comment about this and yes, for multi species multi animal “households” being able to dial it in to fit closer would be a great help.
Possibly even a place where you could input additional animals/needs for a specific case by case basis as in your leopard gecko or a couple of torties? I know one size will never fit all, but that just might make it more user friendly for most people with animals?
Signal_Brain_933@reddit (OP)
Absolutely. I've already got the concept mapped out - a drop-down multi-species animal selector (with a quantity selector) that allows you to factor them all into your plan. Will be working on this in the days ahead. I'll share when it's updated!
Old-Mycologist4750@reddit
Tool cool, thank you so much for sharing this and for the updates you are going to put in place. This is really something helpful for people who want to legitimately be able to prep for their family and animals. The ability to dial in activity level is something that I hadn’t considered, and climate definitely needs to be considered by folks.
Very thoughtfully designed and really appreciate that you are sharing it and refining it even more. Thank you!
Signal_Brain_933@reddit (OP)
You’re super welcome! I’m thrilled that you like enjoy it!
NoContext5149@reddit
I think it’s great to make specific plans, but this is unfairly discounting the “1 gallon per day” advice. 1 gallon per day is perfectly fine advice, and far better for mass marketing for the general public that some complex calculation.
1 gallon per day does include cooking and sanitation. It’s just that this is an emergency minimum. It’s the “just keep you alive” number. Not the amount you need to do strenuous activity, not the number you need to bathe frequently or the amount to take care of pets. It gives you drinking and cooking water (which you drink any you cook with), and a small amount to rinse things or perform basic hygiene.
Some people prep for specific situations or plan to maintain some comforts in an emergency and that’s fine, but you’re misunderstanding what FEMA is trying to do when they recommend 1gal/person a day.
Signal_Brain_933@reddit (OP)
You're not wrong and I probably should have been clearer about that in my post. The 1 gallon figure is an honest minimum for keeping a person alive in a short emergency, and FEMA has never claimed otherwise, totally fair correction.
The gap I'm trying to close is that most people I talk to don't know it's a survival floor, they just treat it as a blanket storage target for their own families. They multiply it by their household size, hit that number, and then they figure they're set for two weeks. The calculator is for those people, it's not an "official" criticism of FEMA's intention.
For my own household, the survival-floor math would give me only about 56 liters for two weeks. So this calculator puts my realistic functional target at 285 liters. Neither number is wrong, they're just both meant to be answering different questions or purposes. The tool answers "what do I actually need to keep my household running," which I think is the more useful question for anyone planning beyond a 72-hour disruption.
unicornofdemocracy@reddit
Its important to note the 1 gallon per day is definitely focused on prolonging survival not actual long term survival. They arent expecting that you are out there digging, building, doing a lot of manual labor like in a SHTF situation. The 1 gallon per day doesnt work in that situation because it isnt meant for that.
Also, realistically, most people even prepper are preping for short term emergencies more than SHTF situations. In fact, as troubling as it is, most people I know arent even prepping for short term emergencies.
Signal_Brain_933@reddit (OP)
Exactly right on both counts. The 1 gallon figure assumes you're sheltering in place, relatively sedentary, not doing hard physical work. Add real exertion to the picture and that number climbs fast. And yeah, most people aren't even at the 72-hour kit stage yet, which is honestly the more pressing problem. Getting people to know their actual baseline number feels like a reasonable first step.
yarnhooksbooks@reddit
This. And it’s meant to be a minimum. Almost everything I’ve ever seen or read that comes from FEMA, Red Cross, or other sources that aren’t random people on the internet who fetishize the end of the world say “*at least*” one gallon per person per day for 3 days. And most say something about including pets in that. Many people don’t have unlimited storage space and it’s better to give them a minimum than to tell them they need to find somewhere in their cramped home to store 15 5 gallon water jugs.
marinuss@reddit
Yeh but I’d guess your 285 liter number is closer to a lifestyle number. The thing about water storage is it’s far more important to hit the 1 gallon a day survival number than your accustomed to number. You can die over two weeks not having access to enough clean water. You’re not going to die if you can’t wash clothes in a bucket or pee in a toilet and flush. Water storage and the 1 gallon number are more for a storm knocked out power and services for a few days or a week and you can survive. Even planning on 4 gallons a day to cover lifestyle stuff you can’t meaningfully store say three months of water. At that point you’re getting into larger treatment projects of expected tainted water.
Signal_Brain_933@reddit (OP)
Yep, totally, survival priority comes first, and I'd never argue someone should skip the 1 gallon floor in favor of a comfort number. That's fair advice for anyone just getting started in preparedness.
The one place I'm not sure about is the framing of 285L as a "lifestyle" number. Sanitation in a multi-week disruption or breakdown isn't about comfort, it's about not getting sick when there's no hospital running. Handwashing, basic wound care, keeping food prep surfaces clean to prevent salmonella and other food ilnesses, those matter more in an emergency than in normal life, not less. That's the gap my little water calculator is trying to quantify.
You're completely right that beyond 2-3 weeks, storage isn't really the answer anymore. At that point filtration and collection take over, and no calculator can change that long-term disaster math. This tool is really aimed at the 72-hour to 2-week window (or a month if you push it), getting people to actually know their real number for that range, rather than assuming the gallon rule has them covered when it might not. For a solo adult in a short disruption the 1 gallon/day rule probably holds up. For a family with kids and animals over two weeks... well then the gap gets real fast.
Dependent-Tailor-878@reddit
this is actually really solid work. the 1 gallon rule has always felt like it's written for someone in a bunker with zero variables, and you're right that it doesn't account for the reality most people are living in. my household came out to 4.2 gallons a day and i was shocked because i thought we were already being conservative. the breakdown showing where the water goes is the useful part - now i can actually see that we're burning through water on dishes and laundry more than anything else, which means i can adjust my strategy instead of just doubling the gallon number and hoping.
the livestock comment below yours is a good point too. the calculator doing per-animal estimates is helpful but yeah, you'd need way more granularity if someone's got horses or a bunch of goats. still, this beats the alternative of people either over-prepping with way too much water they'll never use, or under-prepping because the generic advice didn't match their actual situation.
Signal_Brain_933@reddit (OP)
Thank you! Yeah, I'm noting all feedback for V2 - the livestock comments were super helpful, I already know I'm building in this feature for the next deployment.
Dependent-Tailor-878@reddit
That's awesome you're already planning livestock granularity for V2, honestly the biggest gap I see right now is whether someone's storing water just for drinking and basic sanitation versus actually trying to maintain a garden or livestock through an extended outage, which completely changes the math.
Signal_Brain_933@reddit (OP)
Yep, livestock granularity is on the way, I'm hoping to tackle this in the days ahead. Gardening is an interesting variable also, and definitely applicable to longer-term disruption scenarios. I'll see if I can find a accurate way to factor this in, taking into account environment/climate, maybe allowing people to input an estimate of how much water they likely use for gardening in a normal day or week.
Dependent-Tailor-878@reddit
The self-reported approach might actually work better than trying to calculate it - most people already know if they're watering a garden regularly in summer, and asking them to estimate weekly usage is way less friction than building climate models for every region.
Signal_Brain_933@reddit (OP)
Agreed. It may end up being a rough estimate with a margin for error, in case people can't estimate how much water they use for their gardens, or maybe there will be a grid for suggested amounts based on existing data.
Dependent-Tailor-878@reddit
the grid approach would take the guesswork out for people who haven't thought about it yet, and honestly most gardeners can ballpark their summer water use pretty quick if you give them a couple reference points to work from.
Foodforrealpeople@reddit
Government agencies like the CDC and FEMA recommend storing at least one gallon of water per person, per day. .....
so you have 4 people and 1 animal in your household and you came up with 5.4 gallons a day?
That's literally at least 1 gallon a day per household member....................
Signal_Brain_933@reddit (OP)
Close but the comparison doesn't exactly hold up, especially in a longer disruption. FEMA's recommendation for your household would be 4 gallons/day so that's 1 per person, pets not included. The calculator came out to 5.4 gallons/day, which means the dog, cooking water, and basic sanitation account for about 1.4 gallons/day that FEMA's number doesn't cover. To be fair, Fema says a "minimum" number, but a lot of people may just look at the minimum and go with that.
That's not a rounding error, by my count over two weeks it's roughly 20 gallons of uncounted water. Whether that matters depends on how long the disruption lasts and what your fallback options are. If you live by a river and have a good water filter, you're fine. But some people may have different circumstances to deal with.
The "at least" in FEMA's language is doing a lot of work there. It means don't store less than this, not that this is what you actually need.
Foodforrealpeople@reddit
wow.. so you mean the CDC/FEMA minimum recommendations aren't for like months or years of disruption??????????????????????? weird.......
and in a short term disruption (which is the standard for "minimum emergency preparedness) of say 3-7 days a MINIMUM of 1 gallon a day is 100% doable even in HOT weather .....
to account for food preparation and basic hygiene, official disaster guidelines (like the CDC and FEMA) recommend 1 gallon per person, per day.
Planning & Storing Recommendations:
Signal_Brain_933@reddit (OP)
The CDC Food and Water page does list 1 gallon per person per day including pets so using that, my household target under their guidance would be 5 gallons a day (4 people + 1 dog). The calculator puts me at 5.4. So we're arguing over 0.4 gallons a day at that point. The "double for hot climate" and "double for children" multipliers you cited aren't in current CDC guidance that I can find; their current pages say "consider storing more" for those groups without giving a specific multiplier. IMHO it's worth flagging since someone might use that number to plan and find it doesn't come from the source they think it does. The calculator's job is to fill exactly that gap, and give those groups an actual number rather than just saying "store more."
Atlabatsig@reddit
Very well done - thanks. My wife and I live in a very rural area on the west coast, and we've often considered what might most impact our water supply. Bottom line is that (1) a seismic event would likely cause the ground to shift and destroy our well. And then (2) a flood might well destroy the water quality - though we'd probably not be here (physically or mortally) with a flood anyway. And (3) storms, civil collapse, etc. For that, our approach has been to install a switch in our pumphouse so that we can run a small gas generator to pump water - as needed to fill the holding tank. We chose gasoline because it's the fuel we're most likely to have (truck, car, storage, mower, etc) in an unscheduled event. In addition, we keep roughly 130 gal of water - routinely flushed.
As for pets, we are now down to just one horse. About a half mile away is a small pond and creek, so that'll be visited multiple times a day for him.
Signal_Brain_933@reddit (OP)
Wow, that's an impresive setup. I have a 350 foot deep well myself, but I don't have a backup pump setup yet; they're pretty pricey, but I'm saving up for a solar pump backup. Luckily I'm close to a pond also - no horse though!
Atlabatsig@reddit
350' is one deep well. Wow.
As far as cost, I bought this: https://www.homedepot.com/pep/318061467?cm_mmc=ecc-_-STH_OUT_FOR_DELIVERY-_-V1_M1_CB-_-Product_URL&ecc_ord=WG64661959&em_id=a201521dc57fd8e3e54017980d157e996bcce01ed98492d540c9238f6b449bb1
Which wasn't too bad at $529. I think the (manual) switch I installed was maybe $109, and then probably another $50 of wire and outlet.
One of the things people don't seem to talk much about is post-disaster gardening. Being very rural, in a disaster I can easily see it taking 2-3 months for anyone to get to us. So we keep a few small gardens (e.g. 8'x10') and "try" to grow stuff that we can keep thru seasons. Like onions, potatoes, kale, spinach, zucchini, apples, etc. To that end, you and I having those ponds close by is good for retrieving water for watering the veggies, etc. We don't have chickens right now, but we have in the past. Small coop, just 3-4 chickens will provide at least a couple eggs a day thru most of the year.
iambecomesoil@reddit
That's a lot to say that it is pretty close. The difference that you've calculated is 7% more than the recommendation at 1g per person/pet per day.
I think most REASONABLE people understand that this is a survival amount for hydration.
This isn't doing tie-dye, this isn't washing the car, this isn't walking through the desert during the day.
This is about how to get through an emergency/disaster for about 2 weeks and not suffer from dehydration.
Signal_Brain_933@reddit (OP)
The 7% figure comes from dividing my household total by the FEMA total, but that's not quite the right comparison. FEMA's baseline (minimum to be fair) recommendation for my household (2 adults, 2 kids) is 4 gallons a day (no pets, no cooking water, no sanitation). The calculator puts my household at 5.4 gallons. That's a 35% gap, not 7%, and the difference is entirely made up of a large dog, basic cooking, and sanitation (none of which are tie-dye or car washing; my cars are almost unforgiveably dirty on a good day!).
You're totally right that the 1 gallon rule is about not dying from dehydration. No argument there. But the calculator is about not getting sick from something preventable when medical care isn't available. Those are different problems and for me at least, both matter over two weeks.
iambecomesoil@reddit
You're saying FEMA recommends no additional water storage for animals above that as the baseline for the humans?
Signal_Brain_933@reddit (OP)
Fair correction: FEMA does have separate pet preparedness guidance that recommends storing water for animals, but what they don't do is give a specific quantity. It's "several days' supply" with no per-animal figure specified or suggested. So the 1 gallon per person rule doesn't include pets, and FEMA's pet guidance doesn't fill that gap with anything measurable (not yet at least). That's exactly the hole this calculator is trying to close (and will be even more specific in V2 thanks to the feedback in this thread); giving people an actual number for their specific animals rather than just leaving it at a vaguer "store some water for your pet."
NWYthesearelocalboys@reddit
My results: (Results met via swimming pool and fish pond)
OmniPrepper Emergency Water Storage Plan YOUR HOUSEHOLD PROFILE Adults 4 Children (under 12) 1 Special needs Chronic illness / meds Pets 3+ pets / livestock Climate Extreme Heat (>38°C) Activity level Active Planning duration 1 Month Food preparation Some cooking (canned + dry mix) Water currently stored 32000 GAL Daily Requirement 54.3 L 14.3 gal Total Target Storage 1627.9 L 430.1 gal ✓ Storage goal met Category Amount What does this look like? 81 × 20L jerry cans + 2 × 4L jugs = 1628L Drinking water 624.4 L / 165 gal Sanitation & hygiene 499.5 L / 132 gal Food preparation 112.5 L / 29.7 gal Pets 324 L / 85.6 gal Special medical needs 67.5 L / 17.8 gal Total requirement 1627.9 L / 430.1 gal
Signal_Brain_933@reddit (OP)
That's a great result to see! Thanks for sharing, it gives me real life examples to work with. extreme heat, chronic illness needs, 3+ pets/livestock, and you're already well past your storage target. The pool and pond as primary reserves is smart, though you'd need filtration before drinking use in a real disruption (which I'm guessing you already know).
The 324L for pets over a month is the number that usually surprises people in your category. What kind of livestock are you working with? I'm already planning V2 with more pets categories and livestock granularity. Curious how the tool sized up against what you'd estimated before running it.
murphybt@reddit
When I was younger I always read 3 gallons PPPD for drinking, cooking, and sanitation (dish washing, bathing, and clothes washing) so that's what I shoot for. I currently only have about 100 gallons in 5 gallonish containers and the water heater (so 8 days of water for our family of four). In the next 6 months I'll be adding 2 205 gallon Bushman tanks that I'm getting for a total of $100 which will bump me up to about 41 days of water.
The smaller containers are all potable and get refreshed every 6 months straight from the tap. The water heater is obviously potable as well. The outdoor water won't be "purified" but should be drinkable without treatment as they'll be setup according to ARCSA standards.
Signal_Brain_933@reddit (OP)
That's a pretty sweet setup for water storage. Do you live in an environment where water is harder to come by, or that's dependent on the infrastructure?
murphybt@reddit
I live in a smaller city in the SF Bay Area so we usually don't see any rain for at least 6 months every year. The water department IS quite reliable. My main disaster concerns are earthquakes and various two-legged issues. We do have a few lakes/reservoirs around but the idea of trying to collect water there in WROL doesn't sound like a good time. Instead, I was lucky to have purchased a house with a defunct well that was drilled in roughly 1940. I have yet to rehabilitate it but my longer term plans involve the well.
Signal_Brain_933@reddit (OP)
Nice! Did you know about the well when you bought the house; i.e. was it one of the selling points for you? Living in an earthquake prone area, I can imagine something like this would be a diamond in the rough for any home purchase.
murphybt@reddit
I DID know about it and it was definitely nice plus. It's also in a nice little outbuilding 15'x15' approx. that has become my workshop. It's definitely in the rough, the pump is a Jacuzzi Bros. ag pump from the 40s or 50's and is seized. I still need to pull the pump and drop pipe and then get a cap for the 6" casing and then get one of those new hand pumps that are available now. I already have an electric pump from work for normal times irrigation use.
Signal_Brain_933@reddit (OP)
Nice plan - I had a similar plus when buying my house; it needed a lot of work but had a super deep well and was built like a tank by somebody who was already a prep-minded person. It even had a secret room! Not something the real estate agent was advertising, but I could see the benefits immediately.
murphybt@reddit
Awesome! Our house is quite small but there's a great little hidden area that you can only tell exists from the attic when you pull a bunch of insulation out of the way.
Signal_Brain_933@reddit (OP)
Nice! Yeah, bonus is that kids (if you have any around) get a huge kick out a secret hidey-hole!
kkinnison@reddit
Two adults two kids and 1 large dog = 5.4 gallons a day
a gallon a day is close enough. you make up that .4 gallons usuually with the food you eat. and the galloon a day does not assume water for cleaning or sanitation, which tracks with your 5.4 gallon a day for 5 Living beings.
stop thinking too hard about it. Close is good enough
Signal_Brain_933@reddit (OP)
Glad you ran it! 5.4 gallons/day for your household is actually 5.4x the 1 gallon rule, not exactly "close enough" to it. Over two weeks that's pretty much the difference between storing about 8 gallons and storing 75 (napkin math). That gap matters if and when resupply isn't available.
The "food moisture makes up the difference" point is real for pure hydration math (and a totallly valid precision), but stops applying the moment you factor in cooking dry goods, basic sanitation, or your dog on a warm day. For me at least, those aren't luxuries in a 2-week grid down disruption.
"Close is good enough" is fine for a 72-hour kit. Absolutely. For anything longer I'd rather people know the real number and decide how much of it they want to hit.
Inner-Confidence99@reddit
I was taught the one gallon per person per day was just the drinking water for that person/animal.
Water for cooking, bath, toilet were separate from that gallon.
Signal_Brain_933@reddit (OP)
Sometimes I wonder if we're in the 1% of people who can think beyond the simple FEMA-type guidance or calculators, or read between the lines. My assumption is that most 'regular' i.e. non-prep minded people might look at the 1g/person/day rule as being the global rule, not thinking about cooking and hygiene and pets.
beached89@reddit
That is the point. It is supposed to be a global rule for non prep minded people.
No one in a hurricane zone is expected to be washing their car, laundering their daubes, or taking 30m hot showers.
Inner-Confidence99@reddit
I live in the USA- I have personally dealt with surviving tornadoes, flooding, hurricanes and blizzards all my life. In the same state. Was taught to prepare early for all at a young age.
argyle_zebra@reddit
This is super helpful! Thanks so much for sharing.
Signal_Brain_933@reddit (OP)
My pleasure! Thanks for trying it out - feel free to give me feedback if there's anything that needs to be improved!
Senior_Green_3630@reddit
I have a dedicated , filtered, 750 litre/200 US gall of drink water tank and a 6500 litre/1717 US gall , garden water tank. I have never run out of drinking water and my garden tank waters my garden between rain events. I live in a dry/arid area of Aystralia, annual average rainfall, 225 mm or 9 inches. The large tank was subsidised by our local water supplier.
Signal_Brain_933@reddit (OP)
Wow, that's a phenomenal amount of water. And the fact that your local water supplier subsidizes it is epic. Great setup!
Senior_Green_3630@reddit
I am planning to add 1000 litre/265 US gall pod tanks to my garden, I'll squeeze them in between my fruit trees and run PVC down pipes off my shed/carport. Need to paint or cover them with shade cloth to protect from UV, very thin plastic.
Proud-Map-8364@reddit
This is helpful but there is no way a family has enough room to store 210 gallons of water for a month stockpile. Maybe 105 for a 2 week stock. But people need to have other means of getting clean water. Try a water filtration system or water collection system. We are trying to help people to prepare for success and gallons of water will only get you so far if you don’t have any means to replace it.
Signal_Brain_933@reddit (OP)
Yup. Completely agree, stored water alone isn't a full strategy, it's just a starting point. The calculator is designed to answer "how much should I have on hand right now" as a baseline, but not as a substitute for filtration or collection.
And yeah, you're also right that the real prep stack here is storage + filtration + some collection method as per your enviroment. A gravity filter like a Berkey or a Sawyer system dramatically changes what a 2-week supply actually needs to look like. I'm hoping to add or build in some sort of optional filtration and collection section to V2 that ties into the storage number, so showing how much your daily filtration capacity reduces your storage target. Really appreciate you pointing that out!
Good addition for anyone reading my post: if you have a reliable filtration setup, run the calculator, then maybe cut your storage target based on your filter's daily output (factoring in the reliability of your filter). The gap between the two is what you actually need to keep in reserve.
Soil2Star@reddit
Great tool, things like this really help us realize how much water we really need.
We used to live on a very isolated and remote farm. We were surrounded by river, and our closest neighbor was a little over two miles away. Our water source was the river (San Joaquin), and pumped through a sand filter only. You can't see 6 inches in this water so we knew it was a danger to us. It really taught us how to use potable and non-potable water carefully.
Bonus for us was that the power was frequently off for days at a time, one time for almost two weeks. We had the river about 100 feet from the house, but that section was about 15' down and socked in with blackberries. There was an easier access point maybe a quarter mile down the driveway, but hand hauling the buckets up even 10 feet was tough, especially after a few days in.
All this to say we discovered our baselines the hard way. Two people, two medium-sized dogs, two barn/shop cats and three chickens need a minimum of three gallons of water to drink a day. In the kitchen, I needed only about a gallon of non-potable to wash up but I used an average of 1.75 gallons a day for cooking and the daily wipe down with clean water. My husband could shower easily with a not quite full 5g bucket of non-potable water, but I needed more due to my long hair. We are doing pour overs btw. We brushed our teeth and rinsed our faces with bottled water (regular, small bottles) which felt like luxury while dealing with the rest.
If we felt grungy we would shower at a friends, and we did our laundry at friends' houses. It was a great experiment for us, really taught us what we actually need. We also discovered that our 'smaller' generator (I can barely carry it) is enough. We ran it for days straight, with two long corded power strips plugged in. One for the fridge, and the other for two lamps and two chargers. When I miss that place, I reminisce about these times and I miss it a little less.
Signal_Brain_933@reddit (OP)
Great write up! Thank you! I had a similar baseline "lesson learned" (although totally different climate) during the infamous 1998 Quebec Ice Storm which knocked out power for 6 days in winter. You really learn quickly what your water/hygiene needs are when your water is shut off and you're relying on bottled water and buckets to clean up.
And the long hair shower vs short hair shower is a very useful distinction that I wouldn't have thought of. Thank you!
AlwayInForwardMotion@reddit
That’s fun! I think the livestock section could use more specifics. My horses drink about 10 gallons a day, 15 if it’s hot. Goats and llamas maybe 2 gallons a day. Way different than my 20 pound dog or my 60 pound dog. Washing wounds take a good bit of water too. I keep 2 days of water for livestock as backup but anything longer than that and we’re headed for the reservoir. I’m realizing I’ve been under calculating my personal water though and I really appreciate the wake up call!!
Signal_Brain_933@reddit (OP)
Awesome specifics, thanks so much! You're right about livestock - I'll add that to the polish once I get all the feedback I'm hoping for. Maybe a few extra optional tick boxes where users can select and input livestock size, and account for extra "what ifs" like wound washing. If somebody's a nurse or doctor or paramedic, they may get a lot of drop ins from community members wanting first aid, so that's a worthwhile distinction.
AlwayInForwardMotion@reddit
Also possibly worth considering, when I lived without running water I took bucket showers. 3-5 gallons was comfortable for a basic soap on soap off shower. If I was feeling really fancy I set up 2 five gallon buckets for an extra long shower.
Signal_Brain_933@reddit (OP)
Yes! Totally fair - another commenter brought up the "comfort" vs minimum variable. That's noted, an extra tick box for adding a top-up for comfort/luxury or any unaccounted for variable a family might need. V2 will account for this.
AlwayInForwardMotion@reddit
Love it! I’m excited to try it out. A week without a shower and I find it a lot harder to be a happy agreeable person haha.
Signal_Brain_933@reddit (OP)
Lol... thanks! I'm kind of different - if I go camping or backpacking, I'm fine for a few days with wet wipes, but I use the vision of a hot shower as a huge motivator to keep me going knowing it's on the horizon!
Grendle1972@reddit
I have always maintained 5 gallons of water per person is the minimum needed for typical days allowing for drinking, and some hygiene, plus cooking. This is of you are nauseous doing light work, abd mostly sitting around. Here in East Tennessee, during the dinner, I routinely drink 5 liters of water a day easily just doing yard work and cleaning around the house. More wheel, more heat abd humidity or inversely, colder temps equals more water intake.
Signal_Brain_933@reddit (OP)
Absolutely. And if you're a prolific sweaty-inclined person (guilty as charged) or have hyperhidrosis or other medical conditions, your own numbers may vary greatly.
Kitchen-Ebb30@reddit
The pets section could be more specific, since animal sizes and drinking water that's needed is different for dogs vs cats vs horse vs pigs vs sheep...
Signal_Brain_933@reddit (OP)
Good call! right now it lumps pets into small/medium/large which is pretty rough. A horse and a Labrador are obviously not the same problem. V2 will have species-specific inputs, including livestock. Adding it to the list now, thanks for the feedback!
smsff2@reddit
Here's a corrected version that stays close to your original wording:
The good thing is that the app was completely free. I didn't even see any affiliate links, attempts at monetization, or anything like that.
The math is a bit optimistic, though, or I guess pessimistic. It's pessimistic in the sense that you plan to consume more water than the bare physiological minimum. It's optimistic in the sense that you're planning for a leisure-type situation rather than an actual emergency where survival is genuinely in question.
I know that on a hot day, I consume about two liters of water per day. I'm not sure I could consume a full gallon even if I also tried to wash my hands, face, and so on. That's a luxury, not a necessity, though.
I base my calculations on two liters per day. This is the bare minimum for survival. That's exactly what I need for an emergency situation.
Signal_Brain_933@reddit (OP)
Glad it felt clean, thanks!
On the math: yup, you're right that 2L/day keeps a person alive, and if you're solo, healthy, and planning for a true worst-case survival scenario, that's a totally defensible number. no argument there.
Where I'd maybe push back (just a little) is the framing of "leisure" vs "emergency." In a full-on multi-day emergency with kids, pets, and any cooking, the 2L floor could break down fast, not because anyone is being extravagant, but probably because sanitation failures in a disruption scenario are genuinely dangerous. Handwashing isn't a luxury when there's no hospital to go to (and just keeping my kids to wash their hands is already a full time mission!).
The calculator isn't planning for comfort (but actually that may be a useful variable somebody could factor in, maybe I could add a tick box to add a "comfort" top-up). As is it's planning for a household staying functional and healthy for two weeks (or however long you set it) without outside help. Those are different targets than solo survival, and both are definitely worth considering. Thanks for the feedback, really appreciate it!
shikkonin@reddit
No shit. Why do you think they all stress that this is drinking requirements only?
nanneryeeter@reddit
I am always suspicious of conveniently rounded figures.
1G PPPD is absolutely too convenient to match our standard units of measurement.
Having spent a lot of time off-grid, it could be not enough or even too much, depending on factors. I can get by with less if I am near a warm lake that can be used for bathing. I'll need more if poorly sheltered in a hot/windy environment. Truth is, you really don't know until you know. Good post.
Signal_Brain_933@reddit (OP)
Thanks! And yeah, proximity to bathable water is a definite factor, along with environmental variables. I mean I get why rounded figures exist - society as a whole needs easy to remember figures and calculations so there's at least a rough starting point, especially if you live in a disaster-prone area. But personally I like to be more precise and factor in as many of my own family specifics as I can.
Mischeese@reddit
That’s really useful. Thanks so much!
Signal_Brain_933@reddit (OP)
My pleasure! Hope it comes in handy!
Signal_Brain_933@reddit (OP)
MY OWN RESULTS:
3 adults (2 actual adults and one adult sized teenager), 1 child, 1 dog, cold climate, 60 litres of water already stored, no special needs, active level, cooking mixed dry and canned, storing for 2 weeks.
Broken down into four categories (drinking water, sanitation & hygiene, food preparation, pets)
Daily Requirement 20.4 L - 5.4 gal
Total Target Storage 285.3 - 75.4 gal
Your household needs 20.4L per day. You have 21% of your 14-day target stored. To close the gap, add 57 × 4L jugs or 12 × 20L jerry cans.