Is my water safe during a power outage?

If you're on a private well, the pump is off

An electric well pump stops when the power does, and with it your running water — use stored or bottled water for drinking, cooking and brushing teeth until it's back. If the outage came with flooding or other damage, the CDC says it is safest to drink bottled water until you are certain your water is free of contaminants and safe to drink. If you suspect the well is contaminated, it advises asking your local or state health department about disinfecting it, leaving that work to a well or pump contractor, and having a qualified electrician, well contractor or pump contractor check the wiring before the power is turned back on for the well.

Boil-water advisories on city water

Water utilities or government agencies issue drinking water advisories when tap water is, or could be, contaminated, the CDC explains, and a boil-water advisory tells you to boil your tap water before using it. Until it is lifted, the CDC says to use commercially bottled water or boiled water for drinking and to prepare and cook food, to brush your teeth with boiled or bottled water, to boil tap water even if it has been through a home filter, and not to drink or use water or ice from your refrigerator's dispensers. Watch your utility's alerts and local news for the notice and the all-clear.

How to make water safe

Per the CDC, boiling is the best way to kill germs in water: bring clear water to a rolling boil for 1 minute (3 minutes above 6,500 ft elevation), then let it cool. If you can't boil, disinfect clear water with unscented household bleach — for bleach that is 5–9% sodium hypochlorite, 8 drops (a little less than ⅛ teaspoon) per gallon; stir and let it stand at least 30 minutes. Filter cloudy water through a clean cloth, paper towel or coffee filter first (or let it settle), and double the bleach if the water is cloudy, murky, colored or very cold.

The EPA adds that the water should then have a slight chlorine odor; if it doesn't, repeat the dose and let it stand another 15 minutes. Boiling or disinfecting cannot make water safe if it contains fuel or toxic chemicals — use bottled water or another source, and ask your health department.

How much to store

Ready.gov recommends storing at least one gallon of water per person per day for several days, for drinking and sanitation — and more in very hot weather, or for children, nursing mothers and anyone sick. Don't forget pets.

Aquariums, sump pumps, and other water risks

An electric sump pump stops in an outage, and so do aquarium pumps and heaters — know where your water shutoff and any backup pump are before a storm. If your basement floods around electrical outlets or a panel, stay out: the Red Cross says not to go into flooded areas or use electrical equipment that may have been submerged, and to have a qualified electrical inspector check the electrical system.

Store water like it matters

Per Ready.gov: buy commercially bottled water and keep it in the sealed original container in a cool, dark place. If you fill your own, use food-grade water storage containers, clean them with dishwashing soap and sanitize them first, and replace water that wasn't commercially bottled every six months. Never ration drinking water unless authorities order it: drink the amount you need today and try to find more for tomorrow, and reduce how much water your body needs by reducing activity and staying cool.

When the pump or the advisory ends

When a boil advisory lifts on city water, follow your water utility's notice, which overrides generic advice — and if it doesn't cover flushing your pipes, ice maker and filters, ask the utility. Until then, the CDC says not to drink or use water from appliances connected to your water line, including the water and ice dispensers in your refrigerator or freezer. On a well, if you suspect contamination after a flood or storm, the CDC advises contacting your local or state health department about disinfection and testing.

The hidden reserve you already own

The CDC lists the water in your home's water-heater tank — the tank connected to your faucets and showerheads, not a heating system's — among the sources of clean water inside the home, along with melted ice cubes made from uncontaminated water and the clear water in a toilet tank (not the bowl) that hasn't been treated with toilet cleaners. Locate the heater's drain valve now and read your manual's instructions before you ever need to use it. (Turn off power or gas to the heater before draining, and let it cool.)

Sanitation when the taps are dry

Set aside part of stored water for hygiene, not just drinking. If you don't have soap and water, the CDC says to use an alcohol-based hand sanitizer that contains at least 60% alcohol — though sanitizers don't remove all germs and work less well on visibly dirty hands. Pool or spa water can be used for personal hygiene and cleaning but not for drinking, per the CDC, and a bucket of it can flush a toilet poured straight into the bowl. Mark drinking and non-drinking containers clearly so nobody drinks the flush bucket.

Watch for the all-clear

Restoration and the lifting of a boil advisory can lag each other. Check your area's status to follow the power outage, and rely on your water utility's official notice for when the tap is safe again.