After an emergency, such as a flood, hurricane, or earthquake, drinking water may not be available or safe to drink. As a result, residents may have to find a source of safe drinking water or know how to treat their water for use.

Prepare an emergency water supply

  • Store at least 1 gallon of water per day for each person and each pet. You should consider storing more water than this for hot climates, for pregnant women, and for persons who are sick.
  • Store at least a 3-day supply of water for each person and each pet.

Water containers (cleaning and storage)

Unopened commercially bottled water is the safest and most reliable emergency water supply.

Use of food-grade water storage containers, such as those found at surplus or camping supply stores, is recommended if you prepare stored water yourself.

Before filling with water, sanitize the containers:

  1. Wash the storage container with dishwashing soap and water and rinse completely.
  2. Sanitize the container with a solution of 1 teaspoon of unscented liquid household chlorine bleach in one quart of water.
  3. Cover the container and shake it well.
  4. Wait at least 30 seconds and pour the sanitizing solution.
  5. Let the empty sanitized container air-dry OR rinse the empty container with clean, safe water.

For proper water storage,

  • Label container as "drinking water" and storage date.
  • Replace stored water every six months.
  • Keep stored water in a cool place.
  • Do not store water containers in direct sunlight.
  • Do not store water containers in areas where toxic substances are present.

Make water safe


Boiling is the surest method to make water safer to drink by killing disease-causing organisms, including viruses, bacteria, and parasites.

If the water is cloudy,

  • Filter it through a clean cloth, paper towel, or coffee filter OR allow it to settle.
  • Draw off the clear water.
  • Bring the clear water to a rolling boil for one minute (at elevations above 6,500 feet, boil for three minutes).
  • Let the boiled water cool.
  • Store the boiled water in clean sanitized containers with tight covers.


Disinfectants can kill most harmful or disease-causing viruses and bacteria but are not as effective in controlling more resistant organisms such as the parasites Cryptosporidium and Giardia.

To disinfect water with unscented household liquid chlorine bleach:

  • Filter the water through a clean cloth, paper towel, or coffee filter OR allow it to settle.
  • Draw off the clear water.
  • Add the following amount of bleach:
  • If the water is cloudy, murky, colored, or very cold, double the amount of bleach added.
  • 1 drop per quart/liter - 4 drops per gallon of unscented standard household bleach
  • Stir the mixture well.
  • Let it stand for 30 minutes or longer before you use it.

To disinfect water with tablets that contain chlorine or iodine:

Follow the manufacturer’s instructions on the label or in the package.

  • Chlorine dioxide can be effective against Cryptosporidium if the manufacturer’s instructions are followed correctly.
  • Iodine and iodine-containing tablets (tetraglycine hydroperiodide) are not effective against Cryptosporidium.
  • There are some parasites found in surface water that chemical disinfection might not destroy, but as chemical disinfection kills most germs use it if you have no other choice.


Many portable water filters can remove disease-causing parasites such as Cryptosporidium and Giardia from drinking water. If you are choosing a portable water filter, try to pick one that has a filter pore size small enough to remove both bacteria and parasites. Most portable water filters do not remove viruses.

Carefully read and follow the manufacturer’s instructions for the water filter you intent to use. After filtering, add a disinfectant to the filtered water to kill any viruses and remaining bacteria.

Finding emergency water sources

Alternative sources of clean water can be found inside and outside the home. Do not drink water that has an unusual odor or color, or that you know or suspect might be contaminated with fuel or toxic chemicals.

The following are possible sources of water:

Inside the home

  • Water from your home’s water heater tank
  • Melted ice cubes made with water that was not contaminated
  • Liquid from canned fruit and vegetables

Outside the home

  • Rainwater
  • Streams, rivers, and other moving bodies of water
  • Ponds and lakes
  • Natural springs

Water from sources outside the home must be treated as described in Make Water Safe. DO not drink water that has an unusual odor or color, or that you know or suspect might be contaminated with fuel or toxic chemicals; use a different source of water.

Donald Marr is the Public Health Emergency Preparedness Coordinator and Medical Reserve Corps Coordinator for Coos Health & Wellness.


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