Water comes first in a household outage plan. A power failure can also interrupt pumping, treatment or access to a dependable supply. This follow-up to our household outage preparation guide explains how to calculate a reserve, then build a realistic plan for longer disruptions.
Start with a daily baseline
CDC recommends at least one gallon per person per day, starting with three days and building toward two weeks when possible. That allowance covers drinking and limited essential uses; it is not a normal household water budget. Add for pets, heat, pregnancy, illness and other needs. Follow CDC emergency water storage guidance.
Water for a family of four: one month through two years
These figures extend that baseline for planning; CDC does not recommend these long-duration stockpiles. We use 30, 90 and 180 days for the month-based examples, and 365 days per year. Quantities are US gallons. Pets and extra needs are not included.
| Planning horizon | Days | 1 person | 4 people |
|---|---|---|---|
| 1 month | 30 | 30 gal | 120 gal |
| 3 months | 90 | 90 gal | 360 gal |
| 6 months | 180 | 180 gal | 720 gal |
| 1 year | 365 | 365 gal | 1,460 gal |
| 2 years | 730 | 730 gal | 2,920 gal |
This article uses a family of four as its main example. Formula: family members × days × daily gallons. To add one person at the one-gallon baseline, add 30, 90, 180, 365 or 730 gallons for the respective periods. To remove one person, subtract that amount. For five people, multiply the four-person total by 5 ÷ 4; for three people, multiply by 3 ÷ 4. Recalculate any extra needs separately. If four people need 1.5 gallons each daily, a 30-day target becomes 180 gallons. That is an example allowance, not a universal requirement. Cooking, washing, flushing, livestock and gardens can require additional water.
Match storage to the time horizon
For one month, decide whether you can safely accommodate the full reserve or need a shorter stored reserve plus a dependable replacement source. Smaller containers can make dispensing and movement easier. Count usable filled volume, not just the capacity printed on an empty tank.
At three and six months, replenishment, access and rotation become central. Identify where replacement water would come from, how you would transport it and how you would keep it safe. A well that requires electricity needs a workable pumping plan. A rain barrel is not automatically a drinking-water system.
At one and two years, treat the figures as a demand estimate for a water system. Assess source reliability through dry periods, treatment, maintenance, spare components and a fallback if the source fails. A large tank alone does not establish a two-year safe supply. Plan where you would obtain help or relocate if safe water became unavailable.
Choose containers and a safe location
Use food-grade containers intended for water and never reuse containers that held toxic chemicals. Follow cleaning instructions, label fill dates and protect stored water from heat, sunlight and chemicals. CDC advises replacing water you fill yourself every six months; follow dates on commercially bottled water.
Water is heavy: using about 8.34 pounds per US gallon, 120 gallons weighs roughly 1,001 pounds before the containers. That calculation is a planning aid, not a structural approval. Check the support and installation requirements for the actual storage location; do not assume an upstairs closet or elevated deck can carry a tank.
Treatment must match the problem
Follow local water advisories and CDC emergency treatment instructions. A filter does not necessarily remove every hazard. Boiling or disinfecting cannot make water contaminated with fuel or toxic chemicals safe. Use a different safe source and seek health-department guidance.
Water supply checklist
- Stored safe drinking water and separate pet allowance.
- Food-grade containers with lids and suitable dispensing equipment.
- Fill-date labels and a written replacement schedule.
- A source, transport and treatment plan appropriate to the actual hazard.
- Separate allowances for cooking, hygiene and other essential uses.
- A fallback if the source, pump or treatment equipment fails.
Start with a manageable reserve and a plan you can maintain. For the broader equipment selection, browse our store.
