How much emergency water to store, and how to keep it safe
Store at least 4 litres (about 1 gallon) of water per person per day: 12 litres each for three days, and 56 litres each for two weeks. Use clean food-grade containers, keep them cool and dark, and replace stored tap water every six months. If you run out, boiling is the most reliable way to make clear water safe to drink.
How much water one person needs
An adult needs roughly 2–3 litres of drinking water a day, more in heat or during physical work. Add water for preparing food, brushing teeth and basic washing, and the common planning figure becomes about 4 litres (1 gallon) per person per day.
| Household | 3 days | 1 week | 2 weeks |
|---|---|---|---|
| 1 person | 12 L | 28 L | 56 L |
| 2 people | 24 L | 56 L | 112 L |
| 4 people | 48 L | 112 L | 224 L |
Add extra for pets (roughly 50–100 ml per kilogram of body weight a day for cats and dogs), for children and nursing mothers, and for anyone who is ill. Do not ration drinking water in an emergency: drink what you need today and look for more tomorrow.
Containers that work
- Unopened bottled water: the simplest option. Keep it in its original packaging and use it before the date on the label.
- Food-grade water containers (jerry cans of 10–20 litres): marked as safe for drinking water, with a tight cap. Smaller ones are easier to carry and pour.
- Cleaned soft-drink bottles (PET): fine for small amounts. Avoid milk and juice cartons; they are hard to clean and break down.
- Never use containers that have held chemicals, fuel or anything non-food.
Tip: Keep at least one container small enough to carry when full. A 20-litre can weighs 20 kilograms.
Filling and storing tap water
Where tap water is safe to drink, it is the cheapest way to build a supply. Wash the container and cap with hot soapy water and rinse it well. Fill it straight from the tap, close it tightly and label it with the date.
- Store it cool, dark and off the floor, away from fuel, paint and cleaning products.
- Replace stored tap water every six months. Use the old water for plants or cleaning.
- If water smells or looks odd when you open it, do not drink it untreated.
Making water safe when the tap stops
If you run out, or if authorities say tap water is unsafe, treat any water you have not stored yourself before drinking it. Let cloudy water settle and pour it through a clean cloth or coffee filter first: treatment works far better on clear water.
- Boiling: bring water to a rolling boil. WHO considers a rolling boil enough to kill bacteria, viruses and parasites; many health agencies add a margin of one minute, or three minutes above about 2,000 metres. Let it cool covered. Boiling does not remove chemicals.
- Household bleach: plain, unscented chlorine bleach can disinfect clear water. The dose depends on the bleach strength, so follow the instructions from your local health authority or on the product, and let the water stand 30 minutes before drinking.
- Water purification tablets and portable filters: follow the maker's instructions exactly, and check what the filter removes. Many remove bacteria and parasites but not viruses or chemicals.
Tip: Water from floods, ditches or near roads and farms may hold chemicals that no home treatment removes. If in doubt, do not drink it.
Hidden water in your home
In a short emergency, your home holds more usable water than you might think. The hot-water tank, ice in the freezer and water in pipes (open the lowest tap after the supply stops) can all help. Water in toilet cisterns can be used for flushing and, if no chemicals were added, treated for other uses. Never drink water from radiators or heating systems.
Questions
How long can you store tap water?
Replace stored tap water every six months. Commercially bottled water can be kept until the date on the label if it stays sealed, cool and out of direct sunlight.
How much water does a family of four need for an emergency?
At 4 litres per person per day, a family of four needs 48 litres for three days and 112 litres for a week, plus extra for pets, hot weather or illness.
Can I drink water from my hot water tank in an emergency?
Usually yes, if the tank is supplied by safe mains water: turn off the power or gas to the heater first, let the water cool, and drain from the tap at the bottom. Treat it if it looks cloudy or rusty.
Does boiling remove everything from water?
No. Boiling kills bacteria, viruses and parasites but does not remove chemicals, fuel or heavy metals. Avoid water that may be contaminated by chemicals.
Sources
This guide is general information, not professional advice. Follow the instructions of your local emergency and health authorities.
Read next
- 72-hour emergency kit: the complete checklist
What to pack in a 72-hour emergency kit: water, food, light, power, first aid, documents and warmth. A printable checklist with tips that keep it useful.
- Types of bunkers and shelters: what each one protects against
Storm shelters, safe rooms, fallout shelters, root cellars and earth-sheltered homes compared: what each protects against and what to check before building.