How to Make Water Safe to Drink

Maintaining a safe water supply is critical during or after an emergency. After a flood the drinking water may not be available or safe to drink for personal use. Never use water that you suspect or have been told is contaminated for any type of cleaning or food preparation such as dishwashing, brushing teeth, washing and cooking food, making ice, or making baby formula.

Floods and other natural disasters can damage wells and contaminate aquifers. Flood waters can contaminate well water with animal waste, human sewage, chemicals, and other contaminants which can lead to illness when used for drinking, bathing, and other hygiene activities.

Contact your local health department or water company to determine that local and federal guidelines are followed and that preparations have been made to protect the water treatment facilities during a disaster.

Note: Drinking caffeinated beverages, soda, and alcohol can speed dehydration.

How to Make Water Safe

Water usually can be made safe to drink by boiling, adding disinfectants, or filtering but it is important to understand that water contaminated with fuel or toxic chemicals will not be made safe by boiling or disinfection. Use a different source of water if you know or suspect that water might be contaminated with fuel or toxic chemicals.

Boiling

If you don’t have safe bottled water, you should boil water to make it safe. Boiling is the surest method to make water safer to drink by killing any disease-causing organisms, including viruses, bacteria, and parasites.

The water will have a distinctive flat taste after it has been boiled. To lessen this you may want to pour the water into a different clean container and let it stand for a few hours. You may also try adding a pinch of salt for each quart of boiled water.

If the water is cloudy,

• Filter it through a clean cloth, paper towel, or coffee filter or allow it to settle.
• Pour off the clear water from the top.
• 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.

If the water is clear,

• 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.

How to Sanitize Water Storage Containers

1. Wash the storage container with dishwashing soap and water and rinse completely with clean water.

2. Sanitize the container by adding a solution made by mixing 1 teaspoon of unscented liquid household chlorine bleach in one quart of water.

3. Cover the container and shake it well so that the sanitizing bleach solution touches all inside surfaces of the container.

4. Wait at least 30 seconds and then pour the sanitizing solution out of the container.

5. Let the empty sanitized container air-dry before use or rinse the empty container with clean, safe water that already is available.

Disinfect Water

If you don’t have clean, safe, bottled water and if boiling is not possible, you often can make water safer to drink by using a disinfectant, such as unscented household chlorine bleach, iodine, or chlorine dioxide tablets. These can kill most harmful organisms, such as viruses and bacteria. However, only chlorine dioxide tablets are effective in controlling more resistant organisms, such as the parasite Cryptosporidium.

To disinfect water,

• Clean and disinfect water containers properly before each use. Use containers that are approved for water storage. Do not use containers previously used to store chemicals or other hazardous materials. 
• Filter it through a clean cloth, paper towel, or coffee filter or allow it to settle. 
• Draw off the clear water. 

When using household chlorine bleach: 

• Add 1/8 teaspoon (or 8 drops; about 0.625 milliliters) of unscented liquid household chlorine (5–6%) bleach for each gallon of clear water (or 2 drops of bleach for each liter or each quart of clear water). Add 1/4 teaspoon (or 16 drops; about 1.50 milliliters) of bleach for each gallon of cloudy water (or 4 drops of bleach for each liter or each quart of cloudy water). Note: Scented bleach contains soap or other chemicals.
• Stir the mixture well. 
• Let it stand for 30 minutes or longer before you use it.
• Store the disinfected water in clean, disinfected containers with tight covers.

When using iodine:

• Follow the manufacturer’s instructions or use the information below:
• Topical iodine (2%): 8 drops/quart
• Iodine Tincture (2%): 8 drops/quart
• Povidone-Iodine (Betadine®) (10%): 4 drops/quart
• For clear water allow the solution to sit for 15 minutes; for cloudy water, 30 minutes. If the temperature is below 40 dF, double these times.

• Store the disinfected water in clean, disinfected containers with tight covers. 
• It should not be used by persons with allergy to iodine, persons with active thyroid disease, or pregnant women.

When using chlorine dioxide tablets: 

• Follow the manufacturer’s instructions. 
• Store the disinfected water in clean, disinfected containers with tight covers.

   

Iodine

Filtering Water

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.

Emergency or Camping Filter

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

Emergency Water Sources

Alternative sources of clean water can be found inside and outside the home. NEVER drink water that has an unusual odor or color, or that you know or suspect might be contaminated with fuel or toxic chemicals.

Inside the Home

• Water from your home’s water heater tank (part of your drinking water system, not your home heating system)

• Melted ice cubes made with water that was not contaminated
• Water from your home’s toilet tank (not from the bowl), if it is clear and has not been chemically treated with toilet cleaners such as those that change the color of the water
• Liquid from canned fruit and vegetables
• Water from swimming pools and spas can be used for personal hygiene, cleaning, and related uses, but it should not be used for drinking.

Listen for reports from local officials for additional information regarding water precautions in your area. It may be necessary to shut off the main water valve to your home to prevent contaminants from entering your piping system.

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 the section above on “How to Make Water Safe.”

Never use water from the following sources:

• Radiators
• Hot water boilers (part of your home heating system)
• Water beds; fungicides added to the water and chemicals in the vinyl may make water dangerous for human consumption.