Uniied States
Environmental Protection
Agency
EMERGENCY DISINFECTION
OF DRINKING WATER
In an emergency situation where regular water service has been interrupted - like a hurricane, flood, or water
pipe breakage - local authorities may recommend using only bottled water, boiled water, or disinfected water
until regular water service is restored. The instructions below show you how to boil and disinfect water to kill
most disease-causing microorganisms that may be present in the water. However, boiling or disinfection will not
destroy other contaminants, such as heavy metals, salts, and most other chemicals.
ONLY USE WATER THAT HAS BEEN PROPERLY DISINFECTED FOR DRINKING, COOKING, MAKING ANY
PREPARED DRINK, WASHING DISHES, AND FOR BRUSHING TEETH.
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Use bottled water or water you have properly prepared and stored as an emergency water supply.
Boil water, if you do not have bottled water. Boiling is sufficient to kill pathogenic bacteria, viruses
and protozoa (WHO, 2015).
- If water is cloudy, let it settle and filter it through a clean cloth, paper towel,
or coffee filter.
- Bring water to a rolling boil for at least one minute. At altitudes above 5,000
feet (1,000 meters), boil water for three minutes.
- Let water cool naturally and store it in clean containers with covers.
- To improve the flat taste of boiled water, add one pinch of salt to each
quart or liter of water, or pour the water from one clean container to
another several times.
Disinfect water using household bleach, if you can't boil water. Only use
regular, unscented chlorine bleach products that are suitable for disinfection
and sanitation as indicated on the label. Do not use scented, color safe, or
bleaches with added cleaners.
- If water is cloudy, let it settle and filter it through a clean cloth, paper towel,
or coffee filter.
- Locate a clean dropper from your medicine cabinet or emergency supply kit.
- Locate a fresh liquid chlorine bleach or liquid chlorine bleach that is stored
at room temperatures for less than one year. The label should say that it
contains 8.25% of sodium hypochlorite.
- Use the table on the next page as a guide to decide how much bleach you
should add to the water, for example, add 6 drops of bleach to each gallon
of water. Double the amount of bleach if the water is cloudy, colored, or
very cold.
- Stir and let stand for 30 minutes. The water should have a slight chlorine
odor. If it doesn't, repeat the dosage and let stand for another 15 minutes
before use.
- If the chlorine taste is too strong, pour the water from one clean container
to another and let it stand for a few hours before use.
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Table 1: Bleach to Water Dose Guidance
1 quart/liter
1 gallon
2 gallons
4 gallons
8 gallons
lount of Liquid Bleach
2 drops
6 drops
12 drops(1/8 teaspoon)
1/4 teaspoon
1/2 teaspoon
t Bleach contains 8.25% sodium hypochlorite.
ADDITIONAL WATER GUIDANCE FOR EMERGENCIES
Prepare and store an emergency water supply. Visit
the Federal Emergency Management Agency (FEMA)
website www.ready.gov/managing-water for
additional guidance on preparing and storing an
emergency water supply.
Look for other sources of water in and around your
home. Although bottled water is your best choice, you
may be able to find other sources of water by melting
ice cubes or draining your hot water tank or pipes.
You should not use water from toilet flush tanks or
bowls, radiators, waterbeds, swimming pools, or spas.
You can also use river or lake water. It is generally
better to use flowing water than still, stagnant water.
However, do not use water with floating material in it
or water that has a dark color or questionable odor.
Regardless of the source, treat the water by following
the instructions on the previous page.
If you have a well on your property that has been
flooded, make sure to disinfect and test the well
water after the flood. Contact your state or local
health department for advice or go to
water.epa.gov/drink/info/well/whatdo.cfm.
Consider how the water looks and how to filter it if
needed. Disinfection does not work as well when
water is cloudy or colored. If
water is cloudy, let it settle.
Then filter the water through
a clean cloth, paper towel, or
coffee filter. Store the
settled and filtered water in
clean containers with covers.
OTHER DISINFECTION METHODS
If you don't have liquid bleach, you can use one of the
other disinfection methods described below.
• Granular calcium hypochlorite. The first step is to
make a chlorine solution that you will use to
disinfect your water. For your safety, do it in a
ventilated area and wear eye protection. Add one
heaping teaspoon (approximately % ounce) of
high-test granular calcium hypochlorite (HTH) to
two gallons of water and stir until the particles
have dissolved. The mixture will produce a
chlorine solution of approximately 500 milligrams
per liter. To disinfect water, add one part of the
chlorine solution to each 100 parts of water you
are treating. This is about the same as adding 1
pint (16 ounces) of the chlorine solution to 12.5
gallons of water. If the chlorine taste is too strong,
pour the water from one clean container to
another and let it stand for a few hours before
use. CAUTION: HTH is a very powerful oxidant.
Follow the instructions on the label for safe
handling and storage of this chemical.
• Common household iodine (or "tincture of
iodine"). You may have iodine in your medicine
cabinet or first aid kit. Add five drops of 2%
tincture of iodine to each quart or liter of water
that you are disinfecting. If the water is cloudy or
colored, add 10 drops of iodine. Stir and let the
water stand for at least 30 minutes before use.
• Water disinfection tablets. You can disinfect
water with tablets that contain chlorine, iodine,
chlorine dioxide, or other disinfecting agents.
These tablets are available online or at
pharmacies and sporting goods stores. Follow the
instructions on the product label as each product
may have a different strength.
MORE INFORMATION
World Health Organization (WHO), 2015. Technical
Briefing on Boil Water.
Safe Drinking Water Hotline 1-800-426-4791
water.epa.gov/drink/hotline
OFFICE OF WATER 4606-M
EPA 816-F-15-003
JUNE 2015
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