How to Make Water Safe to Drink in an Emergency

When to treat water

After floods, hurricanes or water main breaks, local officials may issue a boil water advisory. Follow their instructions exactly. If you use water from any source you aren't sure of, treat it before drinking, cooking, brushing your teeth or making baby formula.

Method 1: Boiling (best)

1. If the water is cloudy, let it settle and pour off the clear water, or filter it through a clean cloth or coffee filter.
2. Bring it to a rolling boil for 1 minute. At elevations above 6,500 feet, boil for 3 minutes.
3. Let it cool, then store it in clean, covered containers.

Method 2: Household bleach

Use only regular, unscented chlorine bleach. Scented, color-safe and splash-less bleaches are not safe for treating water. Check the label for the sodium hypochlorite percentage.

Stir, then wait at least 30 minutes before drinking. The water should have a slight chlorine smell. If it doesn't, repeat the dose and wait another 15 minutes.

Method 3: Purification tablets

Chlorine dioxide or chlorine tablets are compact and easy to keep in a go-bag. Follow the package directions exactly, since wait times vary by product and water temperature.

Method 4: Portable filters

Hollow-fiber filters remove bacteria and protozoa, such as Giardia, and work instantly. Most do not remove viruses, so combine a filter with chemical treatment if the water may be contaminated by sewage.

What treatment can't fix

None of these methods removes chemicals, fuel or toxic substances. If water smells of fuel or chemicals, or flood water may have mixed with industrial runoff, don't drink it. Use your stored supply or bottled water instead.