How much water to store for emergencies and how to store it properly

If you build just one emergency supply, make it water. It’s the most important for survival, the cheapest and the easiest to keep. Yet in many homes, water is the first thing missing when the tap stops after an earthquake, a flood or a power cut that knocks out the building’s pumps.

How much water you need

The figure used by most civil protection agencies is 4 liters per person per day (FEMA says one gallon, about 3.8 liters):

• about 2 liters to drink;
• 1 to 2 liters for cooking, brushing teeth and basic hygiene.

The formula is simple: 4 liters × number of people × number of days. Try it with the sliders above.

People	3 days	7 days	14 days
1	12 L	28 L	56 L
2	24 L	56 L	112 L
3	36 L	84 L	168 L
4	48 L	112 L	224 L
5	60 L	140 L	280 L

Add water for pets (roughly 1 liter a day for a medium dog) and more for babies on formula, sick people and breastfeeding women. For the full calculation, including food, use the supply calculator.

Water for flushing and washing isn’t part of these 4 liters. For that you can use non-drinking water: a bathtub filled in advance, rainwater, large containers.

The simplest option: bottled water

Buy packs of still water and put them aside. They’re sealed, have a clear best-before date and stack easily. Use them in rotation:

1. Write the month you bought it on each pack.
2. Put new packs behind the old ones.
3. When a pack nears its date, bring it to the kitchen and drink it, then buy another.

That way the supply costs nothing extra beyond the initial stock.

Tap water stored in containers

For a bigger supply you can store treated tap water:

• use food-grade plastic containers (marked with the cup-and-fork symbol or the codes 1 PET, 2 HDPE or 4 LDPE), drinking water jerrycans or reused water bottles;
• wash them with water and dish soap, rinse well, then sanitize with a solution of one teaspoon of unscented bleach per liter of water, shaken and left for 30 seconds, and rinse again;
• fill them to the top, close tightly and label with the date;
• replace the water every 6 months.

Never use containers that have held toxic substances, detergents or fuel, even if washed.

Where to keep it

• somewhere dark and cool: a closet, cupboard, under a bed, an unheated room;
• away from chemicals, paint, gasoline or detergents: plastic lets vapors through;
• not directly on concrete (put a pallet or cardboard underneath);
• not on a balcony exposed to sun or frost;
• split it between several places so you don’t lose it all if part of the home becomes inaccessible.

Hidden water in your home

If the supply runs out, there are a few more sources:

• the water heater: tens of liters of drinkable water. Turn off the power or gas, close the cold water inlet and drain it from the tap at the bottom;
• ice in the freezer;
• liquid from canned vegetables and fruit;
• the pipes: open a tap on the top floor, then the lowest one, to drain the remaining water.

Don’t drink water from the toilet cistern if you use cleaning tablets in it, or from radiators or swimming pools.

When water isn’t safe

If authorities say tap water isn’t drinkable (after floods, pipe bursts or contamination), don’t drink it or brush your teeth with it until you’ve treated it. See emergency water purification.

Checklist

• I’ve worked out how much my household needs
• I have bottled water for at least 3 days
• I’ve extended the supply to 7 to 14 days
• Every pack or container has a date on it
• I have purification tablets or a filter
• I know how to drain the water heater
• I have a large container for flushing and washing water