University of Missouri Extension

EMW1026, New March 2012

Safe Drinking Water in an Emergency

Bob Schultheis
Natural Resource Engineering Specialist
University of Missouri Extension in Webster County

You and your family can survive for several days without food, but only a short time without water. Disasters can often cause us to question the safety of our drinking water. With a little planning and preparation, you can be prepared by having a safe emergency water supply.

How much do I need to store?

Store a minimum of one gallon of water per person per day for drinking and cooking. Some of the need for liquids can be met by using juices from canned fruits and vegetables. Additional water will be needed for washing, brushing teeth and washing dishes. Store at least one week’s supply of emergency water for each member of your family.

Do I need to treat the water I’m storing?

It is not necessary to treat water for storage, providing that the water comes from a safe water supply. Public water supplies are already treated and should be free of harmful germs. If stored properly, this water should have an indefinite shelf life. But you may want to rotate and replace this water every 6-12 months with fresh safe water.

Water that might be contaminated with harmful germs should be boiled vigorously for 3 minutes before storage. Water from untested and untreated water supplies, such as a farm pond or a private well, should be purified and treated before storage. To treat water, follow the recommendations in the section “How to purify water.” If you plan to store farm pond or private well water that is to be used in making formula for a baby, it should be purified using the tablet or bleach purification methods below.

How to store water

Food-grade plastic or glass containers are suitable for storing water, provided that they have been completely cleaned. Food-grade containers are any store-bought plastic or glass containers that have previously held food or beverages. Examples include 2-liter soda bottles, water, juice, punch or milk jugs.

Empty bleach containers should NOT be used. These are not food-grade containers. Also, a child may not understand that some bleach bottles are safe to drink out of while others are not. Do not take a chance — the results could be tragic.

Another method of storing water for an extended period of time is to freeze it. Freezing water will allow you to store it in a safe state and use it as you need it. If you lose electricity, the frozen water will also help keep foods frozen in your freezer until power is restored. Make sure you leave enough head space (2-3 inches) in containers before freezing. This will prevent the containers from spilling and breaking. One problem with freezing the family water supply is that you will use a lot of freezer space.

How to purify water


Boil water for 3 minutes in a clean container. Water must be at a rolling or vigorous boil for the entire time.

Tincture of iodine

Add 5 drops of tincture of iodine to 1 quart of clear water, or add 10 drops of tincture of iodine to 1 quart of cloudy water. After mixing thoroughly, allow to stand for at least 30 minutes before drinking.

Purification tablets

These water purification tablets are available at most drug stores. Follow directions on the package.

Bleach purification

If your water supply has come in contact with flood water, you must purify it and the container again before using it for drinking, cooking, brushing teeth or dish washing.

Amount of water Amount of chlorine to add to
Clear water Cloudy water
2 liters 4 drops 1/8 teaspoon
1 gallon 1/8 teaspoon 1/4 teaspoon
5 gallons 1/2 teaspoon 1 teaspoon

Other emergency water sources

Other sources of water supply can come from ice cubes, frozen containers of water, your hot water tank or your toilet tank (not the bowl). Do not drink water taken from the toilet tank if a chemical disinfectant or purifier has been added to the tank.

In earthquake-prone areas, be sure the water heater is strapped or secured to a wall to keep it from falling. Be sure you know where to shut off incoming water to avoid contamination. Turn off gas or electricity to the tank before draining off water for emergency use.

To obtain a free flow of water from the hot water tank, you may need to open the valve at the top of the tank as well as the faucet at the bottom of the tank. You can increase the flow of water from the hot water tank by turning on another hot water faucet in the house before draining the tank.

For more information

Contact your local University of Missouri Extension center:

Adapted from information developed in Fall 1990 by David E. Baker, Extension safety and health specialist, College of Agriculture, Food and Natural Resources; and Melinda Hemmelgarn, former associate food and nutrition specialist, College of Human Environmental Sciences, University of Missouri.
EMW1026 Safe Drinking Water in an Emergency | University of Missouri Extension

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