A flowing tap is not proof of safe water.
The lights fail, and the kitchen faucet still fills a glass. But if water pressure has dropped or a boil-water or do-not-drink advisory is in effect, clear tap water may not be safe. For drinking, cooking, mixing infant formula, and brushing teeth, use unopened bottled water or a properly stored supply known to be safe. Set questionable tap water aside until the water utility or health department gives instructions. A household filter is not a blanket fix: many do not remove microbes, and boiling does not remove chemical contaminants.
How much water to store
Start with one gallon per person per day for at least three days. A four-person household therefore needs a minimum of 12 gallons. That is a starting supply, not a guarantee that every household will have enough.
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Set aside ready-to-drink water for drinking, food preparation, and any medical use that requires safe water. Store extra water separately for washing and cleaning, so those jobs do not consume the drinking supply. Label the containers clearly, especially if any water is not safe to drink.
Increase the total for pets, using their usual daily water consumption as a guide. Heat, heavy activity, and illness can raise drinking needs; infant formula and some medical care may also require a dependable supply of safe water. If a disruption could last beyond three days, extend the calculation for every additional day rather than assuming water will be available for refills. For a step-by-step household estimate, see how to calculate a three-day water supply.
Keep a dependable stored supply
Unopened, commercially bottled water is a dependable emergency supply when its factory seal is intact and it has been stored properly. Check bottles for leaks, damaged caps, or evidence of tampering before setting them aside. Follow any date printed on the package when rotating stock.
Treated tap water can also be stored for drinking if it is safe at the time of filling. Use clean, sanitized food-grade containers with tight-fitting lids; containers that held milk or chemicals are poor choices. Fill without touching the inside of the container or cap, seal immediately, and label each container with its fill date. Replace home-filled water every six months.
Store both kinds of water in a cool place away from direct sunlight, fuel, pesticides, cleaning products, and other chemicals. Inspect the supply periodically for leaks, loose caps, damaged containers, or an unusual smell. Set suspect containers aside rather than tasting the water to decide whether it is safe. Clear appearance does not prove safety: microbes and chemical contaminants may be invisible.
Choose containers that work during an outage
A gallon of water weighs about 8.3 pounds; a full five-gallon container weighs more than 40 pounds before the container itself is counted. Small jugs are easier to lift, carry between rooms, and inspect, though their handles and caps consume shelf space. A 55-gallon barrel holds more in one place but weighs over 450 pounds when full. It needs a suitable, stable location and a clean, food-safe pump or spigot.
Keep at least one small drinking-water container within easy reach, rather than behind heavy supplies or across a dark garage. Check that the route is clear and the container can be opened and poured without power; a battery-powered pump should not be the only dispensing option. Dividing the reserve among several sealed containers also limits the loss if one leaks or its opening becomes contaminated.
Check the source before treating water
Start with intact, sealed water from a known-safe supply. If that runs out, check the local utility or health department’s current advisory before choosing a treatment method. An outage alone does not reveal what is in the water, and clear water is not necessarily safe.
A boil-water advisory generally addresses possible germs after pressure loss or a similar problem. Follow its instructions for drinking, cooking, and brushing teeth; boiling and properly used disinfectants can address many microbial hazards, but neither removes chemical contaminants. A household filter is useful only for the contaminants its manufacturer specifies and certifies it to reduce.
A do-not-drink or do-not-use notice calls for different precautions. If a chemical spill is suspected, do not try to make the water safe by boiling it, adding bleach, or running it through an ordinary filter. Some chemicals can become more concentrated as water evaporates. Use an alternative supply and follow official instructions; filters have limits when chemicals are involved.
Floodwater can introduce both germs and chemicals into a private well. Keep it out of drinking and food preparation until the well has been inspected and tested as directed by the health department and cleared for use. The steps for checking a flooded well matter more than its appearance, smell, or taste. Treat any source of unknown origin as unsafe until its risks are identified.
A boil-water advisory is not permission to boil water suspected of chemical contamination. When the source or hazard is unknown, use known-safe water while awaiting local guidance.
Water heaters are a conditional backup
A tank-style water heater may hold reserve water, but that water is not automatically safe to drink. Its suitability depends on the incoming supply, the plumbing and heater, and when any contamination occurred. Check the local advisory before using it; boiling does not remove chemical contaminants. Tankless heaters provide no stored reserve. For access and system-specific precautions, follow the steps for assessing water from a heater. If its safety cannot be verified, use a known-safe supply instead.
Treat water according to the advisory
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Read the exact notice
A boil-water advisory, a do-not-drink notice, and a do-not-use notice call for different actions. Follow the water utility or health department’s instructions; boiling does not make water contaminated with chemicals safe to drink.
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Start with a suitable source
Use sealed bottled water when available. Treat tap water only if officials say treatment is appropriate for the reported problem. If water is cloudy, let particles settle and pour it through a clean cloth or coffee filter before boiling or disinfecting; removing particles alone does not make it safe.
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Boil when directed and feasible
Bring water to a full rolling boil for one minute, or three minutes above 6,500 feet. Let it cool in a covered container. Ordinary pitcher and refrigerator filters are not substitutes: check what filters can and cannot do during an advisory before relying on one.
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Disinfect only when boiling is unavailable
For water suitable for emergency disinfection, use a method approved by the health department and follow its directions exactly. If the method calls for household bleach, check the specified bleach type and dose; scented, splashless, and additive-containing products are unsuitable. Never guess a quantity.
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Keep treated water clean
Transfer cooled or disinfected water to a clean, covered drinking-water container without touching the inside of the lid or opening. Continue using safe water until officials lift the advisory.
Match the filter to the hazard
For lead, check an independent certification listing for lead reduction on the exact model, such as NSF/ANSI 53. A lead claim says nothing about bacteria or viruses.
Gravity filters vary: some reduce bacteria, but virus protection must be explicitly validated. UV can inactivate microbes in sufficiently clear water, but it does not remove lead or other chemicals.
Compare rated flow and cartridge capacity with the household’s daily drinking-water needs. Slow output or an exhausted element can make a suitable filter impractical during a multiday outage.
Gravity units generally work without electricity; UV units need a charged battery or another dependable power source. Follow the device’s pretreatment and maintenance instructions.
Keep clean water clean
A filter’s clean outlet can still deliver unsafe water if it drains into a dirty jug. Collect treated water in a sanitized, food-grade container with a tight lid. Label containers untreated and treated, and keep their caps, funnels, and scoops separate. Pour water out rather than dipping a cup inside; wash hands with soap and safe water before touching clean openings.
During a multi-day outage, keep containers closed between uses and follow the manufacturer’s schedule for cleaning, backflushing, and cartridge changes. Use safe water for maintenance wherever the instructions require it. Freezing may damage a filter element without leaving visible cracks or changing its flow. Check the manufacturer’s instructions on whether a frozen filter needs replacement before relying on it.
Filtration does not cancel an advisory or establish that an unidentified source is safe. A filter may not remove the hazard named in a do-not-drink notice, and clear water can still contain harmful contaminants. When the source or required treatment is uncertain, use a known-safe supply and follow local health guidance.
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Count the drinking-water supply
Store at least one gallon per person per day for three days, plus more for pets or medical needs. Keep this supply separate from water reserved for cleaning.
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Check and label containers
Mark each container with its fill date and contents. Inspect for leaks, damaged seals, or contamination, and replace or rotate water as needed.
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Prepare a treatment method without electricity
Keep the required equipment and printed instructions together, such as a camp stove and fuel for boiling when the advisory calls for it. Treatment is not a substitute for a safe source when chemicals are suspected.
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Save a route to local advisories
Record the water utility and local health department’s phone numbers and alert channels. Keep a battery-powered radio available if internet and mobile service fail.
Use an authorized water distribution point
If safe stored water is running out, follow local instructions to an authorized distribution point. Do not experiment with a questionable well, floodwater, or another unverified source: boiling and household filters cannot remove every hazard.
