Emergency Drinking Water

Visit the EPA's Emergency Disinfection of Drinking Water page

Storing Water For Emergencies
To be prepared for a drinking water emergency, you should store enough drinking water to supply each person 1 gallon a day for two weeks. This is the amount normally used by one person for drinking, cooking and teeth brushing. The following steps should be used for collecting and then storing the water:

Treating Water In Emergencies
If a safe supply of water is not available, or if your usual supply becomes unsafe for drinking, you must treat the water before it can be used for drinking, cooking, or brushing teeth. There are two ways of treating water: boiling or adding bleach. If the supply has been made unsafe because of untreated surface water (from floods, streams or lakes), boiling is the better treatment.

If the water looks cloudy, it should be filtered before you treat it. You can use coffee filters, towels (paper or cotton), cheese cloth, a cotton plug in a funnel, etc. Use several layers of material for best result. You can also use filters designed for use when camping and backpacking.

Boiling
Boiling is the best way to purify water that is unsafe because of presence of bacteria. Place the water in a clean container and bring it to a full boil and continue boiling for at least 3 minutes. If you are more than 5,000 feet above sea level, you must increase boiling time to at least 5 minutes.

Boiled water should be kept covered while cooling and can be stored in the manner described under "Storing Water For Emergencies."

Purifying By Adding Liquid Bleach
If boiling is not possible, the water can be made safe for drinking by treating with liquid household chlorine bleach (such as Clorox, Purex, etc.) Avoid using scented and "color-safe" bleaches. Household bleach has a strength of about 5% chlorine (most labels show it as 5.25%).

Place the water (filtered if necessary) in a clean container, add the amount of bleach according to the tables below. It is important to mix thoroughly and allow to stand for at least 30 minutes before using the water. If the water is cloudy, or very cold, increase the standing time to 60 minutes. For treating small amounts of water, you may find it easier to use a 1% bleach solution.

You can also use water to purifying tablets or chemicals designed for use when camping or backpacking. Always follow the directions on the package.

Note: Chlorine and other chemicals will not kill cysts of the parasite Cryptosporidium ("Crypto"), which may be present in water supplies affected by untreated surface water. Cryptosporidium is an organism that can cause severe illness and even death in persons who have been weakened because of health problems. Boiling is the best water treatment in these situations.

Very Important
The treatments described above work only in situations where the water is unsafe because of the presence of bacteria. If you suspect the water is unsafe because of chemicals, oils, poisonous substances, sewage, etc., do not use the water for drinking.


How to make a 1% bleach solution:
Mix 1 part of 5% household bleach and 4 parts clean water by volume to give 5 parts 1% bleach solution. For example, 1 ounce bleach to 4 ounces of water or 1 cup bleach to 4 cups water.

Keep bleach solutions in tightly capped containers and labeled to it's strength. Store in a cool place. Discard and make fresh solutions every 6 months.

Chlorine Bleach Solution to add for clean water, or to keep water safe
Amount of water to be treated Amount of bleach solution add
Using 1% solution Using 5% solution
1 quart or 1 liter 10 drops OR 1/8 tsp 3 drops
1/2 gallon or 2 quarts or 2 liters 20 drops OR 1/4 tsp 5 drops
1 gallon 40 drops OR 2.5 mL OR 1/2 tsp 10 drops OR 1/8 tsp
5 gallons 12.5 mL OR 2.5 tsp 50 drops OR 2.5 mL OR 1/2 tsp
10 gallons 25 mL OR 5 tsp 5 mL OR 1 tsp
Important: allow treated water to stand at least 30 minutes before using.
tsp=teaspoon; Tbsp=Tablespoon; mL=milliliter

Chlorine Bleach Solution to add for cloudy water, very cold water, or water coming from surface water sources
Amount of water to be treated Amount of bleach solution to add
Using 1% solution Using 5% solution
1 quart or 1 liter 20 drops OR 1/4 tsp 5 drops
1/2 gallon or 2 quarts or 2 liters 40 drops OR 2.5 mL OR 1/2 tsp 10 drops OR 1/8 tsp
1 gallon 5 mL OR 1 tsp 20 drops OR 1/4 tsp
5 gallons 25 mL OR 5 tsp 5 mL OR 1 tsp
10 gallons 50 mL OR 10 tsp OR 3 Tbsp 10 mL OR 2 tsp
Important: Allow treated water to stand at least 60 minutes before using
tsp=teaspoon; Tbsp=Tablespoon; mL=milliliter