Barring immediate medical emergencies and personal safety, water should be your biggest priority in an emergency situation. You can live much longer without food than water. Dehydration is very dangerous. It affects judgment, causes disorientation, dizziness, stomach pains, headaches, nausea, muscle cramps. This is not only dangerous but it also makes you useless to your family or team members and will, in fact, create more of a burden on them. 15% loss of body fluids can be fatal. Some types of foods may need to be reconstituted. Some folks don’t seem to realize that when your power is off, so is your water in many cases.
Disciplined, healthy adults and children can survive adequately on ½ gallon per day in emergencies if activity is kept to a minimum and the temperature is mild. The accepted amount of water to store is 1 gallon per day per adult. For the most part, this amount only covers drinking and maybe a tad for cooking. If you want enough for bathing, add a gallon per day. Of course, children will use proportionately less. When planning your storage amounts, remember that any dried foods or grains that you store will require water to reconstitute.
If you have any forewarning of a water outage, fill the bathtubs and sinks. Use this water for personal hygiene, cooking and flushing toilets. Get the most out of every drop of water. After bathing and washing hands, put that water in the toilet storage tank for flushing. Do not flush toilet more than once daily if there is no solid waste in it. It will never fill and run over with liquid unless there is a stoppage in the line somewhere.
Don’t let all those thermoses and camping jugs sit around empty. Those containers will take up no more room full than they do empty. Bleach jugs are the perfect vessel to store water in. Rinse lightly with water and fill. The trace amount of bleach left behind will ensure safe water when you use it later. Milk jugs are translucent and allow sunlight to reach your water and do not seal or hold up as well as bleach bottles. If you must use them, store in dark area and check them regularly. Also, if you have room, plastic, food-grade 30 or 55 gallon barrels are great for storing larger amounts of water.
Storing water - What to put it in--Camping cans, plastic cans and buckets, 15, 30 and 55 gal. drums. Add siphon hose or siphon pump. Water heater, bathtub, toilets and sinks are all good storage vessels. Be careful that you don't store it where it will freeze in cold weather. Save wash water for flushing toilets.
Obtaining water -- Irrigation canals, drainage ditches, at culverts, rain gutters, etc. Catch dew and rain. Build a solar still.
Filtering and purification --It's hard to store enough for long term. Family of 4 needs minimum of 120 gallons for 1 month. More for cooking and personal hygiene.
Filtering -- Filtering units and portable bottles. Filtering does not always mean purifying and vice versa. Make sure that you have made provisions to to both filter and purify any water that you have to get from questionable sources
Purifying -- Boiling, iodine, chlorine, Colloidal Silver, filters like Katydyn.
If you purchase commercial filters, here are the approximate sizes of the things that need to be removed from the water. Viruses (hepatitis, polio, etc)- .02-.2 microns, Bacterias (e-coli, salmonella, cholera)- .2-.5 microns, Protozoans (Giardia) 1.0-1.5 Microns.
1. Iodine - Put 5 drops in a quart of clear water and 10 drops cloudy or ice cold water, stir and let stand 30 min.
2. Chlorine - Use regular, unscented chlorine bleach such as Clorox or Purex. Put 2 drops per quart of water, 8 drops per gallon or ½ tsp. per 5 gallons of clear water and double if water is cloudy or very cold. Iodine is a little more effective than chlorine. Chlorine is not effective against Tuberculosis or Giardia and is also a carcinogenic.
3. Boiling- Boiling is the most certain way of killing all microorganisms. There is considerable controversy about how long is long enough to boil water to be 100% effective. One commonly accepted method is to boil for 1 minute at sea level and add 1 minute for each additional 1000' of elevation.
Water temperatures above 160° F (70° C) kill all pathogens within 30 minutes and above 185° F (85° C) within a few minutes. So in the time it takes for the water to reach the boiling point (212° F or 100° C) from 160° F (70° C), all pathogens will be killed, even at high altitude. To be extra safe, let the water boil rapidly for one minute, especially at higher altitudes since water boils at a lower temperature.
4. My personal favorite these days is colloidal silver. It is much more effective and faster than either chlorine or iodine. Add 1 tablespoon of CS per gallon of water, shake, wait 6 minutes, shake again and drink. ½ teaspoon per gallon is recommended but as cheap as CS is to make, I use a little more to be sure.
5. Commercial purification tablets are available at most sporting goods stores and are accompanied by directions.