Bleach can be unreliable for long term storage in emergency preparedness kits for disinfecting water. There is an alternative.
Use Calcium Hypochlorite to Disinfect Water
A 1-pound pag of calcium hypochlorite in granular form will treat up to 10,000 gallons of drinking water
Calcium hypochlorite is one of the best chemical disinfectants for water, much better than household bleach. It destroys a variety of disease causing organisms including bacteria, yeast, fungus, spores, and viruses.
Calcium Hypochlorite is widely available for use as swimming pool chlorine tablets or white powder (pool shock) that is much more stable than chlorine.
How to Disinfect Water Using Calcium Hypochlorite
Using granular calcium hypochlorite to disinfect water is a two step process.
To make a chlorine solution (do not drink this!) dissolve 1 teaspoon (about one-quarter of an ounce) of (78%) granular calcium hypochlorite for each two gallons of water.
To disinfect water add one part of the chlorine solution to 100 parts water to be treated.
Let the mixture sit for at least one-half hour before drinking.
Once the dry granular calcium hypochlorite is made into a liquid solution it will begin to degrade. Due to this you should make your treated drinking water in small batches, for example enough for a couple weeks at a time at most.
Another plus for using calcium hypochlorite to disinfect water for emergency use is that a little goes a very long way. A 1-pound pag of calcium hypochlorite in granular typically costs only a few dollars and you can find it in any swimming pool supply store or the pool section of your hardware store.
Calcium hypochlorite will store for a long period of time and remain effective as a chemical drinking water treatment. It lasts far longer and treats far more water than the traditional chlorine bleach water disinfection treatment.