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This is from an EPA goverment site. Bleach does not work on "all" water.
Jonni in TX
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Emergency Disinfection of Drinking Water

EPA 810-F-93-002
July 1993
In times of extreme crisis, local health departments may urge consumers to
use more caution or to follow additional measures. If local public health
department information differs from this advice, the local information
should prevail.
When the home water supply is interrupted by natural or other forms of
disaster, you can obtain limited amounts of water by draining your hot water
tank or melting ice cubes. In most cases, well water is the preferred source
of drinking water. If it is not available and river or lake water must be
used, avoid sources containing floating material and water with a dark color
or an odor.
When emergency disinfection is necessary, examine the physical condition of
the water. Disinfectants are less effective in cloudy water. Filter murky or
colored water through clean cloths or allow it to settle, and draw off the
clean water for disinfection. Water prepared for disinfection should be
stored only in clean, tightly covered, containers, not subject to corrosion.
There are two general methods by which small quantities of water can be
effectively disinfected. One method is boiling. It is the most positive
method by which water can be made bacterially safe to drink. Another method
is chemical treatment. If applied with care, certain chemicals will make
most water free from harmful or pathogenic organisms.

METHODS OF EMERGENCY DISINFECTION
Boiling: Vigorous boiling for one minute will kill any disease-causing
microorganisms present in water (at altitudes above one mile, boil for three
minutes). The flat taste of boiled water can be improved by pouring it back
and forth from one container to another (called aeration), by allowing it to
stand for a few hours, or by adding a small pinch of salt for each quart of
water boiled.
Chemical treatment: When boiling is not practical, chemical disinfection
should be used. The two chemicals commonly used are chlorine and iodine.
Chlorine and iodine are somewhat effective in protecting against exposure to
Giardia, but may not be effective in controlling Cryptosporidium. Therefore,
use iodine or chlorine only to disinfect well water (as opposed to surface
water sources such as rivers, lakes, and springs), because well water is
unlikely to contain these disease causing organisms. Chlorine is generally
more effective than iodine in controlling Giardia, and both disinfectants
work much better in warmer water.

CHLORINE METHODS
Chlorine Bleach: When boiling is not practical, chemical disinfection should
be used. Common household bleach contains a chlorine compound that will
disinfect water. The procedure to be followed is usually written on the
label. When the necessary procedure is not given, find the percentage of
available chlorine on the label and use the information in the following
tabulation as a guide.
Available Chlorine Drops per Quart of Clear Water
1% 10
4-6% 2
7-10% 1

(If strength is unknown, add ten drops per quart of water. Double amount of
chlorine for cloudy or colored water or water that is extremely cold.)
The treated water should be mixed thoroughly and allowed to stand,
preferably covered, for 30 minutes. The water should have a slight chlorine
odor; if not, repeat the dosage and allow the water to stand for an
additional 15 minutes. If the treated water has too strong a chlorine taste,
it can be made more pleasing by allowing the water to stand exposed to the
air for a few hours or by pouring it from one clean container to another
several times.
Granular Calcium Hypochlorite. Add and dissolve one heaping teaspoon of
high-test granular calcium hypochlorite (approximately 1/4 ounce) for each
two gallons of water. The mixture will produce a stock chlorine solution of
approximately 500 mg/L, since the calcium hypochlorite has an available
chlorine equal to 70 percent of its weight. To disinfect water, add the
chlorine solution in the ratio of one part of chlorine solution to each 100
parts of water to be treated. This is roughly equal to adding 1 pint (16
oz.) of stock chlorine to each 12.5 gallons of water to be disinfected. To
remove any objectionable chlorine odor, aerate the water as described above.

Chlorine Tablets.Chlorine tablets containing the necessary dosage for
drinking water disinfection can be purchased in a commercially prepared
form. These tablets are available from drug and sporting goods stores and
should be used as stated in the instructions. When instructions are not
available, use one tablet for each quart of water to be purified.

TINCTURE OF IODINE
Common household iodine from the medicine chest or first aid kit may be used
to disinfect water. Add five drops of 2 percent United States Pharmacopeia
(U.S.P.) Tincture of iodine to each quart of clear water. For cloudy water
add ten drops and let the solution stand for at least 30 minutes.

IODINE TABLETS
Commercially prepared iodine tablets containing the necessary dosage for
drinking water disinfection can be purchased at drug and sporting goods
stores. They should be used as stated. When instructions are not available,
use one tablet for each quart of water to be purified.
WATER TO BE USED FOR DRINKING, COOKING, MAKING ANY PREPARED DRINK, OR
BRUSHING THE TEETH SHOULD BE PROPERLY DISINFECTED.



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