The short answer
Start with at least one gallon of water per person per day for three days. Two people need at least six gallons; four people need at least twelve. Add water for pets, pregnancy, illness, medical needs, and hot conditions. Three days is the minimum starting amount in current CDC guidance. Build toward two weeks when space and cost permit.
Start here
- Multiply the number of people in the household by three days and one gallon.
- Add water for pets and for health, pregnancy, or heat-related needs.
- Use unopened bottled water or clean food-grade storage containers.
- Record where it is stored and when each container needs replacement.
Calculate the starting amount
Use this baseline: number of people × 3 days × 1 gallon. This water covers drinking, cooking, brushing teeth, and other essential uses.
Three days is a minimum starting amount, not an ideal maximum. CDC advises trying to store two weeks when possible. Meet the three-day baseline first, then add days over time.
- Add water for pets.
- Add water for pregnancy, illness, or medical needs.
- Add water for hot climates or seasons.
- Ask a veterinarian when an animal's appropriate amount is not clear.
Choose water that can remain safe
Unopened commercially bottled water is the safest and most reliable option for an emergency reserve. Keep it sealed and follow the manufacturer's expiration date.
For water filled at home, use clean food-grade containers with tight lids. Durable containers with narrow openings are easier to protect from contamination. Follow the CDC cleaning and sanitizing procedure, label the container Drinking water, add the fill date, and replace the water every six months.
Store it where it can be used
- Keep water cool, away from direct sunlight and toxic substances.
- Split the reserve into containers household members can safely lift and pour.
- Do not put the entire reserve where one leak, freeze, or access problem could affect it.
- Make at least part of the reserve accessible to someone who cannot lift a large container.
- Do not count ordinary bathtub water as stored drinking water.
Maintain the reserve
Check the reserve at least twice a year and whenever the household changes. Replace a container if it leaks, its seal fails, it is damaged, or the water may have been contaminated.
When using a reusable container, pour or use a clean utensil. Do not put hands into the water or touch the inside of the container or lid.
What not to do
- Do not treat three days as the ideal maximum.
- Do not count an ordinary bathtub as potable storage.
- Do not use a container that previously held bleach, pesticides, fuel, or another toxic chemical.
- Do not let a partial reserve become invisible. Record what is stored and what is still needed.
What changes this answer
General guidance becomes a personal decision through these details.
The number of people, pregnancies, health needs, and anyone who uses extra water for care.
Species, size, food, health, and temperature can all change the amount.
Hot conditions can increase water needs and affect suitable storage locations.
Container size, lifting ability, budget, and where water can stay cool and accessible.
Where this guidance stops
- This guide does not calculate pet quantities or individual medical water needs.
- It does not make contaminated water safe. Follow current public-health instructions for treatment or replacement.
- A two-week reserve is an aspiration, not a verdict on households with limited space or budget.
Sources
Consequential guidance is checked against the linked source material.
- Centers for Disease Control and Prevention. How to Create an Emergency Water Supply. Updated June 27, 2025. Checked September 4, 2026.
- Centers for Disease Control and Prevention. How to Make Water Safe in an Emergency. Updated September 19, 2024. Checked September 4, 2026.
- Centers for Disease Control and Prevention. Preparing for Floods. Checked September 4, 2026.
General information, not advice tailored to you or a guarantee of safety. You are responsible for decisions about your safety. Follow current directions from local authorities. Read the safety disclaimer.