How Much Water to Store for an Emergency (Per Person)

Quick answer: Store at least 4 litres (1 US gallon) per person per day, for drinking and basic hygiene. Aim for 3 days as a minimum and 2 weeks if you can. Store more for hot weather, nursing mothers, sick people and pets. Use clean, food-grade containers, keep them cool and dark, and replace self-filled water every 6 months.

Water is the first thing to run out when the taps stop. You can go weeks with little food, but only days without water. The good news: water is cheap, easy to store and simple to rotate. A family can build a solid reserve in a weekend.

How much water per person per day?

Official guidance is remarkably consistent. Ready.gov and the US CDC say to store at least 1 gallon (about 3.8 litres) per person per day, for drinking and sanitation. The UK government’s Be Ready campaign suggests 3 litres per person per day just for drinking, plus more for cooking and washing. Round it to 4 litres and you have an easy number to plan with.

That 4 litres covers drinking, a little food preparation and minimal washing. It is a floor, not a comfortable amount.

When you need more

Plan for extra water if any of these apply:

Hot climate or summer outages. People sweat more and need to drink more.
Pregnant or nursing. The CDC and Ready.gov both flag nursing mothers as needing more.
Illness. Fever, vomiting and diarrhoea all increase fluid needs.
Babies on powdered formula. You need safe water to mix every feed (see babies and pets in emergencies).
Pets. Dogs and cats need their own supply. Ask your vet how much your animal drinks.
Dried food. Rice, pasta and beans need water to cook.

How many days?

Goal	Per person	Family of 4
3 days (minimum)	12 L (3 US gal)	48 L (12 US gal)
1 week	28 L (7 US gal)	112 L (28 US gal)
2 weeks (recommended if possible)	56 L (14 US gal)	224 L (56 US gal)
1 month	120 L (30 US gal)	480 L (120 US gal)

The American Red Cross suggests a 3-day supply for evacuation and a 2-week supply for home. The EU now asks households to be ready to cope on their own for at least 72 hours. Your local civil-protection agency may give a different figure, so check what applies where you live.

Want a number for your own home? Check how many days your household would last. The free calculator works out your water target from your household and climate.

Choosing containers

The easiest option is commercially bottled water in its sealed original packaging. It is clean, labelled and ready to go. Keep it in a cool, dark place and watch the date.

If you fill your own containers:

Use food-grade containers. Look for water jerrycans or barrels sold for drinking water or camping.
Pick tight lids and narrow necks. They are easier to pour and harder to contaminate.
Avoid glass. It breaks.
Never reuse containers that held chemicals, fuel or anything non-food.
Skip milk and juice bottles. Milk proteins and fruit sugars are hard to clean out and can grow bacteria.

Size matters

Water weighs 1 kg per litre (about 8.3 lb per US gallon). A 20-litre jerrycan weighs 20 kg (44 lb), which most adults can still lift. A 200-litre barrel is great for a garage but cannot be moved once full, so you need a pump or tap. A mix of 5–20 litre containers is the most practical for most homes.

How to clean and fill

Wash the container with dish soap and rinse it well.
Sanitise it. Ready.gov suggests 1 teaspoon of unscented household chlorine bleach per quart (about 1 litre) of water. Swish it to coat all surfaces.
Rinse with clean water.
Fill with clean tap water. Treated municipal water needs nothing added.
Close tightly and label with the date filled.

Storing and rotating water

Keep it cool and dark. Sunlight encourages algae and heat can degrade plastic.
Keep it off concrete floors and away from petrol, paint, pesticides and cleaning products.
Replace self-filled water every 6 months. This is the CDC and Ready.gov guidance.
Follow the date on bottled water.
Spread it around. A few containers in different rooms is safer than one big stash.

Set a reminder. Many people swap their water when the clocks change, or at the start and middle of each year. Use the old water for plants or cleaning, then refill. For more on rotating supplies, read our guide to food rotation and FIFO.

Hidden water reserves already in your home

If the taps stop without warning, you may have more water than you think.

Hot-water cylinder (geyser or water heater)

A hot-water tank holds a lot of clean water. The CDC notes a typical tank holds 30–80 US gallons (about 115–300 litres). To use it safely:

Switch off the power or gas to the heater first. Heating an empty tank can damage it.
Let the water cool.
Close the cold-water inlet valve so dirty mains water cannot flow in if supply returns.
Open a hot tap in the house to let air in, then drain from the valve at the bottom.

The first water out may contain sediment. Let it settle and treat it before drinking if you are unsure.

Toilet cistern (tank)

The water in the tank behind the toilet, not the bowl, can be used in an emergency. The CDC says only use it if it is clear and has not been treated with chemical cleaners, such as the blocks that turn the water blue. Boil or disinfect it before drinking.

Other sources

Ice cubes made from safe water.
Liquid in canned fruit and vegetables.
Water already in the pipes. Open the highest tap in the house, then collect from the lowest one.

How to make water safe to drink

If you are unsure whether water is safe, treat it. Follow any “boil water” notice from your local water authority first.

Boiling (the best method)

The CDC says: bring clear water to a rolling boil for 1 minute. At altitudes above 2,000 m (6,500 ft), boil for 3 minutes. Let it cool and store it in clean, covered containers. If the water is cloudy, let it settle or filter it through a clean cloth first.

Unscented household bleach

If you cannot boil, the CDC gives this ratio for unscented bleach containing 5–9% sodium hypochlorite:

Water	Bleach
1 litre (1 quart)	2 drops (0.1 mL)
1 US gallon (3.8 L)	8 drops (½ mL)
5 US gallons (19 L)	40 drops (2½ mL, ½ teaspoon)

Double the dose if the water is cloudy, coloured or very cold.
Stir and wait at least 30 minutes before drinking.
Use only plain, unscented bleach. No scented, “splash-less” or added-cleaner versions.
Check the concentration on the label. Bleach strength varies by country and brand.

Chlorine does not reliably kill the parasites Cryptosporidium and Giardia. Boiling does.

Filters and tablets

Portable filters remove many bacteria and parasites but, as the CDC notes, most do not remove viruses. Pair a filter with boiling or chemical disinfection for the best protection. Chlorine dioxide tablets used as directed will kill Cryptosporidium; standard chlorine or iodine tablets will not. Always follow the manufacturer’s instructions.

Water contaminated with fuel or toxic chemicals cannot be made safe by boiling or bleach. Do not use it.

Your water checklist

Work out your target: people × days × 4 L, plus extra for heat, babies and pets
Buy or fill food-grade containers, and label them with the date
Store in a cool, dark place away from chemicals
Set a 6-month reminder to rotate self-filled water
Learn where your hot-water cylinder’s power switch and valves are
Keep a bottle of plain unscented bleach and a dropper, or a water filter
Have a pot, a heat source you can use safely, and lids for boiling
Note your water utility’s contact details and how it issues boil-water notices

Start with a few bottles this week and build from there. Every litre you add buys your household more time and more calm.