How much water should you store for an emergency? The most common rule is one gallon (about 3.8 litres) per person per day, for at least three days. That is the U.S. guidance. Germany’s civil protection agency goes further: about 2 litres per person per day for 10 days. Most experts agree that more is better, and that you should add extra for hot weather, children, sick people and pets.
Governments across Europe and North America have been telling people to keep emergency supplies at home. Water is always first on the list, because you can survive weeks without food but only a few days without water. This guide explains how much water to store, why the official numbers differ, and how to keep your supply safe.
How Much Water per Person? The Official Numbers
| Source | Amount per person per day | Recommended duration | Total per person |
|---|---|---|---|
| U.S. (Ready.gov guidance) | 1 gallon (3.8 L) | At least 3 days | 3 gallons (about 11 L) |
| Germany (BBK) | 2 L (1.5 L drinking, 0.5 L cooking) | 10 days | 20 L |
| Humanitarian minimum (Sphere standard) | About 15 L for drinking, cooking and basic hygiene | Long-term crises | — |
These figures look very different, but they measure different things. The German figure covers drinking and cooking only. The U.S. figure adds a little for washing and hygiene. The humanitarian standard covers everything a person needs to stay healthy in a camp or long crisis.
Why the U.S. Says One Gallon a Day
According to Ready Illinois, which follows the federal Ready.gov guidance, one gallon per day breaks down like this:
- Two quarts (about 1.9 L) for drinking. That is roughly what a normally active adult needs.
- Two quarts for food preparation and sanitation. Cooking, brushing teeth and basic washing.
The same guidance warns that hot weather or hard physical work can double how much you need to drink. Children, nursing mothers and people who are ill also need more.
Three days is the minimum because that is how long it can take for help to arrive after a major disaster such as a hurricane, earthquake or widespread power cut.
Why Germany Says Ten Days
Germany’s Federal Office of Civil Protection and Disaster Assistance (BBK) recommends being able to supply yourself for ten days. Its water target is lower per day, about 2 litres, but the period is much longer. For a family of four, that means around 80 litres.
The longer period reflects a different kind of risk. German planners think about long power outages, cyber attacks on infrastructure and supply chain breakdowns, not only natural disasters. The BBK’s preparedness pages also say that a three-day supply already helps a great deal and can be built up step by step.
Our explainer on why governments are telling people to stockpile compares the advice of different countries in detail.
How Much Water for Your Household? A Quick Calculator
| Household | 3 days (1 gal/day) | 10 days (2 L/day) |
|---|---|---|
| 1 adult | 3 gal / 11 L | 20 L |
| 2 adults | 6 gal / 23 L | 40 L |
| 2 adults + 2 children | 12 gal / 45 L | 80 L |
| Add per dog or cat | Extra 0.5–1 gal per day, depending on size | Extra 1–3 L per day |
A simple target for many families: aim for the U.S. amount per day and the German length of time if you have the space. If you do not, start with three days and add more over time.
Who Needs More Water?
- People in hot climates or during a heatwave, when sweating can double fluid needs.
- Pregnant and breastfeeding women, who need extra fluids.
- Babies on formula, because formula must be mixed with safe water.
- Older people and those who are ill, especially with fever or diarrhoea.
- People on certain medicines or medical devices that require water.
- Pets, which are easy to forget in an emergency plan.
How to Store Emergency Water Safely
Knowing how much water to keep is only half the job. It also has to stay safe to drink.
Choose the right containers
- Best: unopened bottled water from a shop. It is sealed and easy to rotate.
- Good: food-grade plastic containers or water canisters, ideally 10–20 litres so they are easy to carry.
- Avoid: milk jugs and juice cartons, which are hard to clean and break down over time, and glass, which can break.
Store it in the right place
Keep water somewhere cool, dark and easy to reach. Light and heat encourage germs to grow. Keep it away from petrol, cleaning products and chemicals, because plastic can absorb fumes.
Rotate your supply
If you fill your own containers with tap water, label them with the date and replace the water every six months. Use the old water for plants or cleaning. Shop-bought bottles can be kept longer, but it is still sensible to use and replace them regularly.
How Much Water for Hygiene and Toilets?
Drinking water is only part of the picture. In a longer outage, keeping clean becomes just as important, because poor hygiene spreads illness quickly.
- Hand washing: keep a separate container with a tap, or use wet wipes and hand sanitiser to save water.
- Toilets: a flush uses several litres. Fill the bathtub or large buckets with non-drinking water at the first warning of an outage, so you can flush manually.
- Dishes: paper plates and cups save a surprising amount of water.
- Personal care: a small bowl of water and a cloth is enough for basic washing.
If you have space, store some extra non-drinking water for these tasks. It does not need to meet drinking standards, so rainwater or older tap water works.
Building a Water Supply on a Budget
You do not need to buy everything at once. A simple step-by-step approach works well:
- Week 1: buy one pack of bottled water per person. That covers the first day or two.
- Week 2: clean a few food-grade containers and fill them with tap water. Label them with the date.
- Week 3: add a canister or two of 10–20 litres for cooking and hygiene.
- Every month: add a little more until you reach your target.
- Every six months: rotate the self-filled containers.
Spreading the cost and effort over a few weeks makes preparation easy. Tap water is very cheap, so the main cost is the containers.
What If You Run Out? Making Water Safe
If your stored water runs out and you are unsure about your tap water, official guidance offers two main options.
- Boil it. Bring clear water to a rolling boil for at least one minute, then let it cool. This is the most reliable method.
- Disinfect it with bleach. Use plain, unscented household bleach. The U.S. guidance is 8 drops per gallon of clear water. Stir and wait 30 minutes before drinking.
Only treat water that looks clear and has no smell. Cloudy water should be filtered through a clean cloth first. Water from your hot water tank or toilet cistern (not the bowl) can also be used in an emergency once treated.
Why Water Comes Before Food
Healthy people can survive several weeks without food, but usually only around three days without water, less in heat. Dehydration also strikes fast: headaches, confusion and weakness can start within a day. That is why every official list puts water at the top.
Water problems are also more likely than many people think. Burst pipes, contamination warnings, heatwaves and long power cuts can all stop tap water from flowing or make it unsafe. Cyber attacks on everyday systems are another risk, as our report on the supermarket cyber attack in Europe shows.
Common Mistakes With Emergency Water
- Storing too little. Many people keep a few bottles and assume it is enough.
- Forgetting hygiene. Washing hands and dishes needs water too.
- Storing it in the garage next to chemicals. Heat and fumes damage both taste and safety.
- Never checking it. Containers can leak or crack over time.
- Keeping it all in one place. If that room floods or is unreachable, you lose everything.
Frequently Asked Questions
How much water should I store per person?
At least one gallon (3.8 litres) per person per day for three days, according to U.S. guidance. Germany recommends 2 litres per person per day for ten days.
How much water does a family of four need for three days?
About 12 gallons, or roughly 45 litres, using the one-gallon rule.
How long can I store tap water?
Replace self-filled containers every six months. Label them with the date you filled them.
Does bottled water expire?
Sealed bottled water keeps for a long time, but the plastic can affect taste over the years. Rotating your supply avoids the problem.
Can I drink water from my hot water tank in an emergency?
Yes, if you turn off the power or gas first and treat the water by boiling or disinfecting it before drinking.
The Bottom Line
How much water you need depends on whose advice you follow, but the basics are simple: at least one gallon per person per day, for at least three days, and more if you can. Store it in clean, sealed containers, keep it cool and dark, and rotate it every six months.
A few minutes of planning today can make a real difference if the taps ever stop running. For the bigger picture on preparedness, including food and power, read our guide to why governments want people to stockpile.