water

Water is problematic for the prepper for several reasons:

It is absolutely essential. Humans can live far longer without food than without water. The rule of thumb is that most people can go three weeks without food and 3 days without water.
Water is bulky. The recommended 1gal/day/person volume takes up a lot of space.
Water is heavy. It weighs over 8#/gallon; to help remember this number there is a saying: "a pint's a pound the world 'round". A 72hr supply of water weight 25# per person. Multiply that by a family of four and that's 100# of water.
Water is all leaky, and must be contained in a leakproof container. :-)

dealing with the challenges of prepping water

get real

Get a real-life understanding of what 1gal/day/person looks and feels like. Gather a three day supply for your family and move it from place to place. See where it fits in your house or car. If you don't have your containers worked out go ahead and use buckets; you don't have to keep this water. After the experiment use it to fill the washing machine, the birdbath, or something similar.

It may be worthwhile to run a scenario that simulates lack of tap water to see how much water you actually need. You may need more or less than 1gal/day/person.
Example: on a rather serious week-long group hike in the Ouchita mountains in 1981, all the hikers packed in all food and treated all water from springs that were encountered about every other day. We each consumed less than 2qts/day (we each carried 2 of the 1qt boy scout canteens in our packs) and that included cooking freeze-dried meals. It took forethought and discipline but was quite possible.
I suspect that 2L/day is sufficient for careful preppers. I will test this hypothesis and will report back.

storage

Storage-in-place is not that challenging. Commercial water jugs and cleaned 2L soda bottles (other than root beer bottles, which are semi-permanently afflicted with root beer smell) are easy to handle and store. They can fit under sinks, in the bottom of closets, etc. Some families use food-safe 55gal barrels to store mass supplies of water. Fill it where you want it; it's over 400# when topped off.

Portable storage is where it gets tough. I do not believe it is practical for all people to carry 3 days supply of water in a Bug Out Bag. For one, there'd be little room for anything else. And the 25# weight would max out the weight many non-robust or non-adult people should carry. For this reason my BOB contains minimal water (2L + canteen) and I will rely on some of the opportunistic collection methods below.

One approach: opportunistic collection

My current thinking is to take measured risk: hydrate beforehand, carry a minimum of water (2L/person/day), manage it carefully, and replenish/stock aggressively as conditions permit in order to secure the recommended 1gal/person/day.

At the individual level, remember to refill your water bottle or canteen whenever you can do so. It's like remembering to use the restroom before you leave -- you never know when you will get the next opportunity. Drink water when you need it; do not try to skimp on your drinking water.
If the water supply gets tight here are some techniques to reduce use of potable water (use your own judgement):

fully hydrate any time you get near a supply of potable water.
minimize exposure to heat (ie, walk or sit in the shade instead of the sun)
perform vigorous activities early the day before it gets hot. If hiking, be on the trail by dawn. Siesta in the afternoon.
use non-potable or unknown water instead of scarce drinking water for purposes other than ingestion (external hygiene, gear maintenance).
use non-potable or unknown water instead of scarce drinking water for cooking water that will be boiled anyhow as part of preparation
observe urine color to check for proper hydration; dehydrated people have darker urine.

At the family level, there are a couple of important factors. The first is water use education - model careful water use for your kids. Consider some nontraditional hygiene techniques.
At volumes required for families, and particularly when on the move, the most convenient (empty) container with meaningful capacity (when full) may be the 5gal collapsible water carrier. They are $5-$10 at walmart. A couple of these in the trunk or house would allow for quick/easy capture of any additional potable water you encounter. Highly recommended.

Water trailers and other large containers do exist for automotive purposes, but I do not know that they are that practical. A trailer can carry lots of water but stick out like a sore thumb. You don't want zombies to go all thunderdome on you to get that supply... Another thing rarely considered is that water is so heavy that carrying 100gal or so may cause your vehicle to strain under stop/go evac traffic conditions, will drastically reduce mileage when fuel is at a premium, will cause weird and possibly unsafe handling, may exceed your cars carrying capacity. A broken car in the middle of an evac is not a Good Thing.

The last resort is collection of water in the wild. All water should be considered unsafe unless it comes from the tap or commercial water source. See below for discussion on working with non-potable water.

treating non-potable water

Two things are important here: getting the water source to treat and having adequate time planned to do so before you need it. All water should be filtered (through cloth or other material) and settled (allowed to precipitate, then decanted) before the treatment. Chemical treatments will take at least 30 mins, and boiling and recooling may take significantly longer. The filtration step is easy and may be more effective than one might think; one study used four layers of saree dress fabric and removed 99% of cholera cells in the water sample. Not safe to drink at that point but still it gives your chemical processes a better chance of working and should increase clarity and flavor acceptability.

The method most people know is the boiling method. This is also widely considered the safest method.
FEMA recommends a 3-5min rolling boil. Water can absorb a great deal of heat before boiling so it may be useful to practice boiling water on your emergency gear before you need it. Be aware that long heating times mean high fuel consumption no matter what fuel you are using. You may make your heating system more efficient by using foil or other material to block wind and contain heat.
Note: there is an argument that keeping a boil is unnecessary because the time spent between 180F and onset of the boil is sufficient for effective sanitation. This may be something to remember if you are very short of fuel.

Many people have also heard of the bleach chlorination method. According to FEMA a good rule of thumb is to use 16 drops of unscented bleach (5.25% sodium hypochlorite)per gallon of water and let sit for at least 30mins. You may want to do this a day or say ahead of time to give the chlorine a chance to evaporate out (leave the cap open or loose). After the minimum treatment time is elapsed you may speed the exit of chlorine by pouring back and forth.
Note: bleach and iodine treatments work best in water at or above 70F.
Note: there are some indications that chlorine treatment may not kill cryptosporidium or giardia.
Another note: some sources (including FEMA sources) indicate that clear, non-smelly, "close-to-drinking" water like compromised tap water can be made safe at a 8 drops/gallon level + 30mins.
Tip: the Fema rate of bleach treatment would be about 1cc of bleach per gallon of water, or 5cc/5gal. Syringes are extremely valuable for measuring small amounts of sanitizers and do not take up much space.
Experimental Tip (exercise your own good judgement!): the addition of bleach to water raises the pH of the water (makes it more alkaline) which unfortunately makes the solution far less effective as a germ-killer. 6.7-7.5 is optimal and anything above 8 is radically less effective. A trick used by some homebrewers is to add bleach to the water, mix in well, then add in an identical measure of an acidifying agent (vinegar). This drops the pH into the right range and the bleach chlorination method becomes more effective against giardia, which the uncorrected treatment cannot reliably kill. Note that the vinegar is added to the stirred water/bleach mixture. Vinegar is never allowed to contact bleach directly; Bad Things would occur as they learned in WWI in the trenches. The added effectiveness is caused by a greater production of hypochlorous acid (the bleach smell) so oddly enough this treated water may smell more "bleachy" than with bleach addition alone.

Iodine treatment is familiar to many military, camping, and scouting folks. The effectiveness and limitations of the chemical treatment are similar to the uncorrected bleach treatment above, with the exception that iodine may be more effective against giardia. The main difference is some people may find the iodine objectionable and I hear some people are allergic to it. Bottles of iodine tabs are tiny, light, and easy to carry. Iodine tabs are dosed in sizes that make them most effective for canteen-sized amounts of water. There is also a form of purifier ("Polar Pure") where some water is added to iodine crystals in a bottle then poured back into the water to be purified. I have no experience with the crystal type.

You can use 2% iodine tincture for larger quantities, although the different sources claim anywhere from 4 drops/gallon, 12 drops/gallon, or 20 drops/gallon for clear water. The most common number appears to be 20 drops/gal for clear water, 40 drops/gal for cloudy). Some have reported that after the 30min disinfectant period that a crushed Vitamin C tablet will neutralize the odd color and flavor of iodine. Although iodine chemical disinfection appears to be somewhat more effective than chlorine bleach, many sites recommend the bleach method as iodine is poisonous in tincture/tablet form. The wildly differing recommend dilution rates may make bleach a safer bet.

Back-of-the-envelope cost analysis: $5 of iodine tabs will treat 12.5 gallons, $5 of 2% iodine tincture will treat 50 gallons, and $5 of chlorine bleach will treat 5200 gallons.

Commercial water purifying filters like those from MSR or Katadynare probably good short-term solutions, but they are $$$ and if the SHTF replacement filter will not be widely available. I prefer the chemical techniques given above.

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