Drinking water in an emergency: how much to store and how to make it safe
Reviewed on
About 3 liters per person per day: 1.5 for drinking, 0.5 for cooking and 1 for basic hygiene. For 72 hours that's 9 liters per person, and double the drinking water if it's very hot. The calculator gives you the total for your home, pets included.
Work out what your home needs (works offline)How much water to store
| Water per person per day | 3 L per adult: 1.5 L for drinking, 0.5 L for cooking and 1 L for basic hygiene. 3.5 L for people over 65 and 2.5 L for children (BLE (Germany), 10-day supply table, 2024; Ready.gov (US) recommends 3.8 L (1 gallon) for drinking and hygiene; Sweden, 3–5 L) |
|---|---|
| Basic hygiene | 2–6 L per person per day (the calculator uses 1 L, the minimum; store more if you can) (Sphere Handbook, minimum standards for water and sanitation) |
| Intense heat | It can double the water needed for drinking (Ready.gov (FEMA)) |
| Breastfeeding | +700 ml of water and about +500 kcal a day (EFSA, reference values for water (2010) and energy (2013)) |
| Water for pets | About 50–60 ml per kg per day: small dog 0.4 L, medium 1 L, large 2 L; cat 0.3 L (Common veterinary reference (it varies with heat, activity and wet food). Canada asks for more margin: 4 L a day per medium dog and 1 L per cat) |
How to store it
- Bottled water: the safest option. Respect the best-before date and store it in the dark, away from heat and chemicals (plastic lets odors through).
- Tap water: in clean, tightly sealed food-grade containers (not old bleach or milk containers, which don't clean well). Replace it every 6 months.
- Write the date you filled it on each jug.
How to make it safe
- 1. If it's cloudy, clear it. Let it settle and strain it through a clean cloth, a coffee filter or a paper towel. This doesn't disinfect it: it just makes the next steps work.
- 2. Boil it. The safest method: 1 minute at a rolling boil (3 minutes above 2,000 m / 6,500 ft). Let it cool covered.
- 3. Or disinfect it with bleach. If you can't boil it: bleach labeled as suitable for disinfecting drinking water, with no fragrance or detergent. 2 drops per liter (4 if the water is cloudy or very cold), stir and wait 30 minutes. It should smell slightly of chlorine; if not, repeat the dose and wait another 15 minutes.
- 4. Tablets or filters. Purification tablets and portable filters work if you follow the maker's instructions. Many filters don't remove viruses: combine them with boiling or chlorine.
Drops of bleach by liters
| Liters | Drops (clear water) · Drops (cloudy or cold water) |
|---|---|
| 1 L | 2 · 4 |
| 2 L | 4 · 8 |
| 5 L | 10 · 20 |
| 8 L | 16 · 32 |
| 10 L | 20 · 40 |
| 20 L | 40 · 80 |
Wait 30 minutes before drinking. Only use bleach suitable for drinking water, with no fragrance or detergent.
- Water contaminated with diesel, chemicals or floodwater can't be fixed by boiling or with bleach. Don't drink it.
- For baby bottles, use bottled or boiled water, never water treated only with bleach.
Figures and sources
| Boiling water | 1 minute; 3 minutes above 2,000 m (6,500 feet) (CDC) |
|---|---|
| Bleach | 2 drops per liter of 5–8% bleach (4 if cloudy) and a 30-minute wait (CDC and EPA. In Spain, only bleach labeled as suitable for disinfecting drinking water) |
| Rotating stored water | Every 6 months if it's tap water; bottled water, by its date (Ready.gov (FEMA) and CDC) |