Emergency water: store it, filter it, purify it, collect it

Water jugs, a blue 5-gallon container, a stainless gravity filter, a small dropper bottle and a pot on a camp stove, on a pantry floor

Water is the first number to get right: 1 gallon per person per day, so a family of four needs 12 gallons for 3 days and 56 for 2 weeks. This page covers the four ways to have it when the tap stops: water you stored, water you filter, water you purify and water you collect.

1 gallonper person, per day

For drinking and sanitation (Ready.gov). A family of 4 needs 12 gallons for 3 days.

6 monthsreplace water you bottled

Self-filled containers get fresh water every 6 months; store-bought follows its date (CDC).

1 minuteat a rolling boil

3 minutes above 5,000 feet (EPA).

8 dropsof 6% bleach per gallon

Plain, unscented bleach. Stir, wait 30 minutes, and you should smell a slight chlorine odor.

Store · Filter · Purify · Collect

Store it

Store at least 1 gallon per person per day for 3 days, and 2 weeks if you can (CDC). Use food-grade containers with tight lids, never glass, and never a jug that held bleach or pesticides. Write the fill date on each one.

The full storage guide, from jugs to 55-gallon barrels and long-term rotation: Emergency water storage.

Filter it

A filter strains out what’s in the water. What it removes depends on the filter, and the makers’ claims and certifications differ, so compare before you rely on one for a household.

Our head-to-head of the filters people ask about most, including LifeStraw, Sawyer and Berkey: Best survival water filter.

Purify it

Boiling is the standard: a rolling boil for at least 1 minute, 3 minutes above 5,000 feet (EPA). Without heat, EPA’s bleach dose for 6% bleach is 8 drops per gallon; for 8.25% bleach it’s 6 drops. Double it if the water is cloudy, colored or very cold, then wait 30 minutes.

Water purification without boiling · Iodine and chlorine tablets · Solar disinfection (SODIS)

Collect it

Rain off a roof is a water supply, and how much you can catch is arithmetic: roof area times rainfall. What you’re allowed to collect depends on your state, and rainwater needs treating before you drink it.

Rainwater harvesting setup · Drought and water scarcity

When the power goes, water is one of four clocks. The free Power Outage Survival Guide has the water math for every household size and the 72-hour plan.
Get the free guide →

Questions people ask

How much water do I need per person?

At least 1 gallon per person per day: 3 gallons each for 3 days, 14 each for 2 weeks. Store more for anyone pregnant or sick, for pets and in hot weather.

How long does stored water last?

Replace water you bottled yourself every 6 months. Store-bought water follows the date on the bottle.

How much bleach purifies a gallon of water?

8 drops of 6% plain unscented bleach, or 6 drops of 8.25%. Stir, wait 30 minutes, and check for a slight chlorine smell. If there is none, repeat the dose and wait 15 more minutes.

How long do I boil water to make it safe?

A rolling boil for at least 1 minute, or 3 minutes above 5,000 feet.

How long will 100 gallons of water last a family of 4?

25 days at 1 gallon per person per day (100 ÷ 4). In very hot weather, when needs can double, about 12 days.

See also

Power outages: what fails at home, and when · Power outage gear

Figures from Ready.gov’s Build a Kit page, the CDC’s emergency water supply page (27 June 2025) and EPA’s emergency disinfection page (updated 24 February 2026), checked 14 November 2026. Household totals are our arithmetic.