Water is critical to you and your family's survival. Where you are located within the United States may determine its availability to you in a SHTF America scenario. If bottled water is not available and you have not stored any water, relying on tap water for drinking could be risky business without treating it first. The most common danger in untreated water is the presence of bacteria, and in the United States, two bacterium in particular are most common: giardia lambia and cryptosporidium. Both of these germs can cause serious diarrhea, fever, vomiting, weight loss, and fatigue.
Individuals with compromised immune systems due to age or illness can be at considerable risk from water transmitted disease. Other very dangerous bacteria like cholera and e-coli can also be transmitted by contaminated water and these infections can be fatal. Even if you don't die from them, while you have them, you will wish you were dead. All sources of water including rivers, lakes, streams, creeks, reservoirs, ponds, and springs should be considered contaminated to hikers, campers, and the survivalist. Tap water should also be considered contaminated in a flood, severe thunderstorm, or hurricane.
Safe water is pure water. Pure water is processed water. Water may be processed, considered free of contaminants, and safe to drink in a number of ways:
First, by filtering it to remove organic materials and eliminate any particulates, and then bringing the water to a boil. Filtering can be as basic as allowing the water to pass through a clean cloth or t-shirt before boiling. If you take boiling water to the next step, collect the steam, and condense it, you have distilled water. Distilled water is pure H20.
Second, by sunlight. Direct sunlight is a good way to destroy these bacteria, so if you store your filtered water in clear plastic, 2 liter soda bottles, and place them in direct sunlight, the UV rays will activate the oxygen within the water and kill the bacteria. If you live in the southwest deserts it won't take more than 30 minutes on a hot day to purify your water, or fry an egg on the hood of your car, for that matter. If the eggs are done, so is your water. If you live in a colder, cloudy climate, you might want to expose your water to the sun for a couple of days. It's going to depend on how much sunlight you get and how intense that sunlight might be. If you have a solar oven (and you better have a solar oven if you are a prepper) use it to concentrate the sunlight on your water. Safe is always better than sorry.
The third way to process your water is by chemical treatment. Chlorine bleach is a cheap and inexpensive disinfectant. You can purchase a gallon of 5% sodium hypochlorite at the Dollar Store or Wal-Mart for a buck to a buck and a half. The standard recipe for safe water is 1/8th of a teaspoon of chlorine bleach per gallon of water, but cryptospordium is a bit resistant to chlorine so you may want to double the dose and shake the bottle vigorously. You need to be able to smell the chlorine. If you can't detect a mild scent of chlorine after treating your water twice, you need to find a new source of water. If not, no matter, you will be doing the next person that comes along a big favor, because he or she will correctly interpret the sign of your white bones bleaching in the sun.
Calcium hypochlorite aka bleaching powder is also used as a water purifier, particularly with hard water. However, if it is not properly stored it has been known to deteriorate rapidly and release toxic chlorine gas. For this reason SHTF America does not recommend using or storing calcium hypochlorite. If you don't use it, you won't store it. If you don't store it, it cannot become fatal to you and your family. Children have a natural curiousity about all things. If you store hazardous chemicals your children need to be educated about those dangers. If they are too young to understand, then hazardous chemicals on site need to be fully secured. If you live in a cloudy climate you may want to incorporate ways two and three together, to ensure your water is safe to drink.
Chlorine, sodium hypochlorite (bleach), and calcium hypochlorite (bleaching powder) are powerful chemicals. Powerful chemicals can be dangerous. Chlorine gas at 1000 ppm can be fatal after only a few deep breaths. Caution is advised when using chemicals. Check with OSHA (http://www.osha.gov/) for particulars if you have any questions about hazardous materials. That's what they do.
Pure water is safe water.