Two figures, two needs
Two recommendations answering two different questions shouldn't be confused.
| Recommendation | What it covers |
|---|---|
| 6 litres / person (SGDSN, 72h) | Drinking only, for three days. This is the official emergency kit figure. |
| 20 litres / person / day (WHO, emergency minimum) | Drinking and basic hygiene. This is a minimum threshold, not a comfort target. |
| 50 litres / person / day (WHO, decent life) | Normal domestic use, outside a strict emergency situation. |
For a 72-hour preparedness plan at home, aiming for 6 litres per person remains the realistic baseline. The WHO figure helps understand why a prolonged water outage remains difficult to live through, even with a complete emergency kit.
The calculation for your household
Simply multiply 6 litres by the number of people in the household, pets included if you have any.
| Household | 72h reserve (drinking) |
|---|---|
| 1 person | 6 litres |
| 2 adults | 12 litres |
| 2 adults + 2 children | 24 litres |
| + a medium-sized dog | + about 3 litres (72h) |
For an infant fed with formula, plan additional water for preparing bottles.
How to store it
- In sealed bottles: the simplest solution, with a shelf life indicated by the manufacturer.
- Away from light and heat, in the same easily accessible place as the rest of the emergency kit.
- Renewed once a year, per the Ministry for Ecological Transition's recommendation for the whole emergency kit.
- Tap water in clean, well-sealed containers also works, but keeps for a shorter time than a sealed commercial bottle.
If water runs out
If your reserve runs out before things return to normal, our guide on water outages and non-potable water details which uses remain possible or not, and where to find distributed water in case of a prefectural order.
Mistakes to avoid
- Relying only on tap water. An outage or contamination can make it unavailable overnight.
- Forgetting pets in the reserve calculation.
- Confusing the survival figure (72h) with normal use. 6 litres is enough to drink for three days, not to live as usual.
- Never checking the dates of bottles stored for several years.
Your water self-sufficiency, calculated for your household
LASTLINE can help you:
- calculate your self-sufficiency in days for water, based on your household's actual composition;
- get a reminder before the expiry date of registered bottles;
- find the map of water points around your home if needed.
LASTLINE doesn't supply the water itself: it helps you track what you've already stored.
Calculate my water self-sufficiencyFrequently asked questions
How many litres of water should be stored per person?
The official « Tous responsables » guide from the SGDSN recommends 6 litres of drinking water per person for 72 hours, for drinking only. The World Health Organization sets the emergency survival minimum, drinking and basic hygiene included, at 20 litres per person per day.
How long does bottled water keep?
Sealed bottled water generally keeps for several months to a few years depending on the manufacturer, with the date shown on the packaging. Once opened, it should be consumed quickly. The Ministry for Ecological Transition recommends renewing your emergency kit, water included, once a year.
Can tap water be stored?
Yes, in clean, well-sealed containers, away from light. It keeps for a shorter time than sealed commercial bottled water and needs to be renewed more regularly.
Sources
- SGDSN, Guide « Tous responsables: face aux risques, agissons », November 2025.
- Ministry for Ecological Transition, Preparing your 72h emergency kit.
- World Health Organization, reference thresholds on water needs in humanitarian situations (20 L/person/day minimum, 50 L/person/day for decent use), widely used by water cooperation bodies.