Environmental Health

Director: Jennifer Johnson
Drinking Water Safety

Emergency Drinking Water Safety

Emergency events such as power outages, floods, and earthquakes often impact drinking water systems. It is very important to understand the status of your drinking water after an emergency. Do not drink, brush teeth, wash or prepare food, or wash dishes with contaminated water. If you are served by a public water system you may be contacted by the system manager or the local government to tell you if it is safe to drink your water. Until you know that your water is safe, take emergency measures.

  • Use your stored emergency water supplies. Conserve safe water for essential needs such as drinking and food preparation.
  • Use water from your hot water tank. You will have a drain valve on the tank that you can use to fill containers if your household water lines are compromised.
  • Fill water containers at emergency shelters.

Make Water Safe
Water often can be made safe to drink by boiling, adding disinfectants, or filtering.
IMPORTANT: 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 disease-causing organisms, including viruses, bacteria, and parasites.
You can improve the flat taste of boiled water by pouring it from one container to another and then allowing it to stand for a few hours, OR by adding a pinch of salt for each quart or liter of boiled water.
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.

    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.

Disinfectants
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).
    • 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.
    • Store the disinfected water in clean, disinfected containers with tight covers.
  • When using chlorine dioxide tablets:
    • Follow the manufacturer's instructions.
    • Store the disinfected water in clean, disinfected containers with tight covers.

Filters
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 such as iodine, chlorine, or chlorine dioxide to the filtered water to kill any viruses and remaining bacteria.