That is for the drinking part, what about cooking? I know I use quite a bit of water in my cooking. I boil water for pasta, I use it to make rice, I use it to make almost half of my weekly dishes or sometimes more. I wash chicken thoroughly with water, and it takes water to clean a fish for cooking. I would want a gallon a day for cooking purposes.
Sanitation of foods and eating and cooking utensils. Again a big user of water. I have a dishwasher but I like to do dishes by hand. It seems that I have to wash the dishes before putting them in the dishwasher to be sure they come out clean. So it seems redundant to use the machine. I have tried to get my dishes down to a minimum of water usage to see how much it takes. This also will depend on how many people I am feeding. There is a method to using the least water possible for dishes. Let's take a look at it.
Take 2 dishpans (which is an item you will need in your storage) One dishpan will have very hot water with about a teaspoon of dish detergent or a bar of plain soap such as Ivory soap with your washing cloth. I suggest you stock reusable gloves to do this as well. The other pan will have water as well for rinsing. Now the first step to cleaning up is to immediately after eating take your dish scrape all food off and then wipe your plate or bowl down with a piece of newpaper or your used paper napkin or part of a paper towel. When you have all food particles that can be taken off you wash your dish or bowl in the soapy water or with the soap on your rag. Then you rinse and put in your drainer. Let air dry. Sounds like it is too simplistic? Well, the point is to keep your dishwater as clean as possible. You will use this same dishwater for the whole day. If your dishpans are metal then you can reheat the water over your rocket stove or cooking fire to wash at the next meal and so on. Now if you are smart you will reuse this water for other things after you finish your dishes in the evening. That water is still pretty clean even though it has soap in it. I would be good for washing your hands or washing your underclothes out in and then you can take that water out and water your garden with it as long as the soap level is not too much. At least you can water your fruit trees. Now as for the rinse water. It is tommorrows dish water and you will start a new rinse water. Is that understandable. Water can be reheated as often as you need for making your dishes sparkling clean.
If you are using rainwater to wash your dishes you may want to add a teaspoon of bleach to your water just to be sure it is as clean as possible. If you use cast iron cookware be careful not to burn food inside of it. If you do though you may want to soak with a little hot water for an hour and then scrape any crust left in it off and then use a teflon style of scrubby to finish it. You do not use soap in cast iron. It will take off your seasoning! If you are cooking over an open flame the outside will probably get sooty but don't worry about it. Just use a little sand to remove it by scrubbing with a damp cloth and just wipe it down with a dry rag. Always re oil your cast iron after cleaning to keep it from rusting. I want you to remember that if you use rain water for dishwashing it takes less soap to wash because rainwater is soft water with no minerals in it to speak of. Same for washing your body.
Speaking of washing your body, learn to take bird baths. A quart of water should wash your whole body pretty thoroughly. Wet a wash cloth and only use soap on the cloth do not put the cloth back in the water. Start with your face and neck and wash your upper body next and then your legs and then your genitalia then your feet last. The only time you wash your feet before your genitalia is if you have sores or blisters on your feet so that you don't get them infected. The next step will be to rinse with a clean wet cloth and then towel dry. If you do it this way you and your spouse or a couple of kids can wash out of the same basin before the water is gone because the water stays clean. I suggest you buy white wash cloths so you can soak them in a little bleach water to clean them and then hang them to air dry. You may want to put initials on the corner of the cloths so that the same person always uses his own two cloths. Sound extreme? Not when you don't have water from your faucet any longer. Rain catchment in most areas will be adequate for drinking, dishes and washing your body but won't be enough to waste. Areas that are in desert climates should invest in large cisterns if they don't already have them and they will still need to be super sparing of their water because they may not be able to get more water delivered.
Now if you happen to have a deep well and the means to pump it that is free of the grid you will have an easier time of it. I would suggest if you have a deep well and you are dependent on the grid you check out Solar power or Wind power to pump it. That is a given. You may have a generator but what will you do to pump your water after you fuel runs out? You may check into wood gas generators or methane powered generators but those will only be good if you have great amounts of wood or lots of animals to produce methane from their waste.
Now let's talk about how to catch your rain water if you can in your area. Many companies have plastic food barrels that are from foods that are sold to restaurants and canneries or large instutional kitchens. These barrels are usually bought by a middle man and resold to the public. They are perfectly fine for your catchment system with the knowledge that you will have to clean them. Some are easier than others. Depending on what was stored in them. Dill or sour pickles will have a pretty strong smell and will continue to have the vinegar odor after thorough scrubbing. Don't let this worry you, time will diminish the odor and it is not dangerous in any way. You probably won't smell the odor after you remove the water from the barrel for use. Any barrel that had oil in it will need to be need to be pressure washed with dish detergent and water. The oil is not something you want in your water for any purpose so be careful to clean it thoroughly. There are many youtube videos which show how to set up your rain catchment system. Just type Rain Catchment into the you tube search bar. You will need a gutter system or a valley in your roof to direct your water into your barrels. You can connect your barrels into a system with overflow from one barrel to another. I understand you can collect hundreds of gallons of rain water with a one inch rainfall if you have enough roof to direct the water.
Next for those of you who cannot catch rainwater from your roof because of an asbestos tile roof left from the "old days" or because you live in an apartment or condo etc. You may want to consider catching your water in an umbrella turned upside down in a bucket or new trash can on your patio. I saw this on Southernprepper1's channel on You Tube also he showed another idea that would be a creative one. He showed a pick up truck bed lined with clear plastic as a rain catchment system. You just have to collect the water from the plastic liner and put it into buckets or barrels after your storm goes through. If their was no other use for your truck because of no fuel or the computer was burned out by an EMP or CME then at least the truck bed would be useful to collect rainwater.
An small above ground pool could be used the same way. Childrens pools could help you to collect water and then could be put away after the rain was over and you stored the water. Be creative and do what you have to to survive. don't forget to collect your rainwater promptly and filter any debri out of it and then you might want to treat it with a little bleach to be sure it is clean for drinking and washing.
Now let's talk about ways to put a lot of water away inside your home that will see you through the first few weeks or even months depending on your situation. Do you drink Sodas? Do you buy it in cans or 2 liter bottles? Start buying it in 2 liters and you will have containers for free and that will hold up well to water storage. They are safe to store water in as well as with the 2 qt. juice bottles which apple juice, grape juice and fruit fusion juices come in. As long as they are the harder plastic bottles they will work just as well as the soda bottles. Store your water in the bottles standing upright in the bottom of your closets. You can put cardboard or lightweight thin wood sheeting on top of the sodas and still have the area for your shoes and sweater boxes etc. that you would normally keep on the floor. I have two walk in closets floors covered in the perimeter with water.
For the final part of the water talk let's talk about treating water. Clean water that you store now put 4 to 6 drops of plain unscented bleach into each 2 liter or 2 quart bottle. Then change out your water every 6 months to a year. Just to be sure it stays fresh and good tasting. If you have to drink it and it passes the time limit just boil it and/or put a few more drops of bleach into it and then pour it from one pitcher to another one several times to aerate it and make it more pleasant flavor wise.
If you are using suspect water that may be contaminated or dirty like out of a pond, lake or river you should filter your water and boil your water. You don't want to get a water born disease. Getting a water born disease could cause severe vomiting and diareah and could cause severe dehydration and with no medical help you could be in deep trouble. The following was found on the internet: This comes from the site Rehydration Project at http://rehydrate.org/solutions/homemade.htm
Rehydration Project - rehydrate.org - 2 January, 2012
You can make a homemade filter just like the expensive Berkeys for less than half the price by buying the filters from Berkey and putting together your own system from 5 gal buckets and lids from Home Depot and the only other purchase would be a spigot for the bottom bucket. The instructions for this are on the net as well. Check out this video on You Tube: http://www.youtube.com/watch?v=XYG_TLoI9O4&feature=fvsr
I would also prefilter your dirty water by pouring it through a piece of tightly woven cloth first or coffee filters will work as well. I personally would like to boil the water after putting it through both filters just to be sure it is safe to drink. There are many different filters that you can buy but I am trying to save you money and still make you safe. Always be careful to drink only clean water that has been treated or boiled or filtered or all three in a situation where you doubt the safety of the water.
I guess that is about all that I can think of to tell you at this moment in time. If I think of more I will share it with you later.
Remember: Every journey begins with the first step and you have to take that first step to begin your journey to your goal......