Water is the first thing that runs out and the last thing you want to be scrambling for. You can survive about three days without it, but you'll be impaired long before that — headaches, confusion, and bad decision-making start within a day of mild dehydration, which is exactly when you most need a clear head. A little storage and a couple of purification methods solve this problem for a few dollars, and they're the single highest-leverage piece of emergency prep you can do.
How Much to Store
The FEMA baseline is one gallon per person per day, and that is genuinely a minimum — it covers drinking and very light cooking, but not a shower or much handwashing. A more realistic number for a household that wants to stay reasonably clean is closer to 1.5–2 gallons per person per day.
For duration:
- 3 days (about 3 gallons per person) is the hard floor. This is what FEMA recommends every household have on hand. For most short outages it's enough.
- 14 days (about 14 gallons per person) is what experienced preppers actually store. It sounds like a lot, but it's four of the standard 3.5-gallon water bricks per person, which stack neatly in a closet or garage. It covers a real multi-day outage with comfortable use and some to spare for a neighbor.
- Don't forget pets. A medium dog drinks roughly 0.5–1 gallon per day; a cat much less.
For a family of four, 14 days works out to about 56 gallons. Stored in food-grade 7-gallon stackable containers, that's eight containers — extremely manageable.
The Right Containers
The container matters more than people think. Bad plastic ruins stored water faster than any contamination does.
Use:
- Food-grade water storage containers (the blue or clear stackable jugs sold for emergency water). Look for HDPE (#2) or PET (#1) and a "food grade" marking. These are designed to store water for years without leaching or degrading.
- Original, unopened commercially bottled water. Fine, but expensive for a 14-day supply and the bottles have a 1–2 year shelf life.
- Stainless steel or glass for short-term indoor storage (not ideal for bulk).
Do not use:
- Milk jugs. They're designed to degrade — they'll leak within months and were never meant to seal water.
- Bleach or chemical jugs, even rinsed. Residue is impossible to fully remove and the plastic is not food-grade.
- Used soda/juice bottles are okay in a pinch if thoroughly washed, but the threading doesn't seal as well as a real water container and they're more likely to pick up off-tastes.
Before filling a new container, rinse it with a weak bleach solution (1 teaspoon unscented household bleach per quart of water), rinse again with clean water, then fill.
Where and How to Store
- Cool, dark, and dry. Heat and sunlight degrade plastic and accelerate taste and contamination issues. A basement or interior closet is ideal; a garage is acceptable if you won't exceed ~85°F for long stretches.
- Off the ground and away from chemicals. Don't store water directly on concrete (it can wick moisture and chemicals through the container) or near gasoline, pesticides, or anything with strong fumes.
- Label with the date so you know when to rotate.
- Don't put water near your emergency food — if a container leaks you don't want it ruining your food supply.
Rotation
Stored water doesn't really "expire," but it doesn't stay perfect forever. Over 6–12 months the taste degrades (from tiny amounts of plastic permeation and the container off-gassing), and if your seal wasn't perfect, you can get biological growth.
A simple plan: dump and refill every 6 months, or at minimum once a year. Use a daylight-saving time change as your reminder. The old water is fine for watering plants or flushing toilets.
Other Water Sources in Your Home
When stored water runs low, you have options most people forget:
- The hot water heater holds 30–50 gallons of potable water. Shut off the inlet valve (so contaminated water doesn't backflow in) and drain from the bottom spigot into a clean container. If the heater was upright and the water was clear, it's safe to drink.
- Toilet tank water (the tank, not the bowl) is potable if you haven't used drop-in cleaners. Use it for pets or boiling.
- Ice cube trays and drink pitchers are a few extra cups at the start of an outage — grab them early.
- Swimming pool or hot tub water is not safe to drink due to chemicals, but it's great for flushing toilets and washing.
How to Purify Water When You Need To
If you're working from a questionable source — a stream, rain catchment, tap water under a boil notice, or water that's been sitting uncovered — there are three reliable methods. Boiling is the most foolproof; the others are backups.
1. Boiling (most reliable)
Bring water to a rolling boil for 1 minute (or 3 minutes above 6,500 feet, where water boils at a lower temperature). This kills bacteria, viruses, and parasites — the threats that actually make people sick. Boiling doesn't remove chemical contamination or cloudiness, so filter cloudy water through a cloth first if you can, and don't rely on boiling if the water may be chemically contaminated (e.g., floodwater near industrial sites).
2. Unscented household bleach
Standard 6% sodium hypochlorite household bleach, unscented and unexpired, is a perfectly good emergency purifier:
- Clear water: 8 drops per gallon
- Cloudy water: 16 drops per gallon (double)
Stir and let stand 30 minutes. There should be a faint chlorine smell at the end — if there isn't, the water was overly contaminated, and you should repeat the dose and wait another 15–30 minutes. If it still has no chlorine smell, discard it — the water was too contaminated for this method.
3. A water filter (good to own)
A certified portable water filter (look for one rated to NSF/ANSI P231 or the EPA microbiological guide, which actually tests for virus removal) is worth keeping with your emergency kit. Cheaper filters remove bacteria and protozoa but not viruses, which is fine for clear, remote backcountry water but less reassuring for urban disaster water. Pair a filter with a pre-filter cloth for sediment.
What Doesn't Work
- Freezing does not reliably purify water — some pathogens survive it.
- Letting water "sit" in the sun does virtually nothing in a useful timeframe.
- UV from a window doesn't reach the water column reliably; purpose-built UV pens work but only on already-clear water.
- Alcohol, iodine from first-aid kits, or other home remedies are not reliable purifiers for emergency drinking water.
The Sensible Setup
- 2 weeks of stored water in food-grade containers, rotated annually.
- A container of unscented bleach in the pantry (label it with a Sharpie for purification ratio).
- One portable filter as a backup, kept with your go-bag.
That's it. For most households it's a single afternoon and maybe $60–100, and it removes the single most likely emergency problem for a fraction of what a generator costs.
For the other half of home prep, see how to build a 72-hour emergency food supply or pack a home go-bag.