How much water to plan for
Ready.gov recommends storing at least one gallon of water per person per day for several days, for drinking and sanitation. It notes that a normally active person needs about three-quarters of a gallon of fluid daily from water and other beverages, and that needs vary with age, health, activity, diet, and climate. Children, nursing mothers, and sick people may need more. In very hot temperatures, water needs can double.
The CDC’s emergency-water page, updated 27 June 2025, says to store at least one gallon per person per day for three days, and to try for a two-week supply if possible, with extra considered for pregnancy, illness, pets, or a hot climate.
Ready.gov also advises: do not ration drinking water unless authorities tell you to. Drink what you need today and look for more for tomorrow. Reduce activity and stay cool to lower demand. Caffeinated drinks and alcohol are not a substitute; they increase the need for water.
Stored water
This is the foundation. It requires no weather, no pump, and no learning curve on a bad night.
- Ready.gov and the CDC both treat unopened commercially bottled water, kept in its original sealed container in a cool, dark place, as the simplest reliable option. Observe the use-by date on store-bought bottles.
- If you fill your own containers, both agencies recommend food-grade water storage. The CDC says to clean with soap, sanitize with 1 teaspoon of unscented household chlorine bleach (label 5%–9% sodium hypochlorite) in 1 quart of water, shake so the solution wets all interior surfaces, wait at least 30 seconds, pour out, air-dry, then fill. Do not reuse containers that held toxic chemicals. Avoid glass, which can break.
- Water you bottled yourself should be replaced every six months, per Ready.gov and the CDC. The CDC suggests storing containers at about 50°F–70°F, away from sunlight and away from gasoline or pesticides, labeled as drinking water with the date.
For a family of four, a three-day store at one gallon per person per day is 12 gallons; two weeks is 56 gallons. That is heavy, but it is also predictable.
Treating uncertain water
If stored supplies run out, Ready.gov says to treat water of uncertain quality before using it for drinking, washing food or dishes, brushing teeth, or making ice. Let sediment settle or strain it through a clean cloth first. Their comparison of household methods:
- Boiling — described as the safest of these methods for killing microbes: a rolling boil for one full minute, then cool. It does not remove heavy metals, salts, or most chemicals.
- Chlorination — regular unscented liquid bleach with 5.25–6.0% sodium hypochlorite as the only active ingredient, at the dose Ready.gov states (1/8 teaspoon per gallon, stir, stand 30 minutes; repeat once if there is no bleach odor). This also targets microbes, not heavy metals or salts. Follow the current official page; do not improvise with scented or “color-safe” bleaches. The CDC’s related pages may state bleach concentrations as 5%–9%; use the instructions that match the bottle you have.
- Distillation — boil and collect only the condensed vapor. Ready.gov says this can remove microbes that resist boiling or chlorination, plus heavy metals, salts, and most other chemicals. It is slower and needs a heat source.
Portable filters and disinfectant tablets can be useful if they are used as directed and match the hazards you actually face (some handle microbes but not chemicals). Look for certifications relevant to the job, and keep the official boil/bleach/distill methods as a backup. This is not a product endorsement of any filter brand.
Rain catchment
A roof, gutters, a first-flush or debris screen, a food-grade tank, and a treatment step can collect a lot of water in a wet climate — and almost none in a drought. Yield is simply rainfall times the catchment area times how much you actually capture, minus losses. We are not inventing a gallons-per-storm figure here; it varies by roof, rainfall, and how tight the system is.
Rain is not automatically potable. Roofs pick up bird droppings, dust, and dissolved materials from the roofing itself. Many places regulate rainwater use, especially for drinking. Check local rules in your US state, Canadian province, Australian state or territory, or UK jurisdiction before you plumb a permanent system. Treat rain as another uncertain source unless you have designed and tested it as drinking water.
Even a modest barrel for garden use can still reserve some treated municipal water for drinking. That is a valid, lower-risk reason to catch rain.
Atmospheric water generation
An AWG condenses (or otherwise harvests) moisture from air. The process is real; the limits are physical. Collection falls when dew point is low. Energy use per liter rises in dry or cold conditions. A 2023 US climate study of commercial units found refrigeration-based energy use ranging from about 0.02 to 3.64 kWh per liter depending on weather, and a 2024 analysis of active AWG technologies recommended treating them as a complementary supply because output fluctuates.
In an emergency, an AWG also needs power. If the grid is down and you have no generator or solar surplus, the machine does not help. Stored water still does.
For the physics, see how atmospheric water generators work and how much water you can pull from air. For one DIY guide sold as digital plans, see our research-based Water Freedom System review. Cedarwell has not built or tested that product.
Disclosure: The review page contains affiliate links. Cedarwell may earn a commission if you buy through them, at no extra cost to you. Full disclosure.
Side-by-side
| Option | Best use | Depends on weather? | Needs power? | Main caution |
|---|---|---|---|---|
| Stored bottled or food-grade water | First hours and days of an outage | No | No | Bulk, rotation, storage temperature |
| Boil / bleach / distill | Making an uncertain source safer in an emergency | No, but you need a source and, for boiling or distilling, heat | Only if your heat source needs it | Follow official doses; chemicals and metals may remain unless you distill |
| Rain catchment | Ongoing supplement in wet climates; garden water | Yes — no rain, no water | Usually no for a simple barrel | Contamination and local regulations |
| Atmospheric water generation | Supplement in warm, humid conditions when power is available | Yes — strongly | Yes, often substantial | Energy cost, climate limits, water still needs treatment and testing |
If you can only do one thing this month, store water. Then add treatment supplies (and official instructions). After that, consider rain or an AWG only if your climate and skills support them.
Sources
- Ready.gov, “Water,” last updated 22 February 2021: ready.gov/water.
- CDC, “How to Create an Emergency Water Supply,” 27 June 2025: CDC emergency water supply.
- “Temporal and spatial variability of energy intensity for atmospheric water generators,” Environmental Research: Infrastructure and Sustainability, 2023, DOI 10.1088/2634-4505/accec9.
- “Energetic analysis and economic viability of active atmospheric water generation technologies,” Discover Applied Sciences, 2024: Springer link.