How much, per the guidance
Ready.gov specifies one gallon of water per person per day for several days, for drinking and sanitation, with at least a three-day supply for evacuation and a two-week supply at home.
Worked through for a household:
| Household | 3 days | 2 weeks | In 7-gallon containers |
|---|
| 1 person | 3 gal | 14 gal | 2 containers |
|---|
| 2 people | 6 gal | 28 gal | 4 containers |
|---|
| 4 people | 12 gal | 56 gal | 8 containers |
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| 4 people plus a dog | ~14 gal | ~63 gal | 9 containers |
|---|
Calculated from Ready.gov's one gallon per person per day. Pets need water too and are routinely left out of the arithmetic — allow roughly a gallon a day for a large dog. Ready.gov also notes that hot weather, pregnancy and illness all increase the requirement.
The two-week figure looks like a lot of plastic. In practice most households store the three-day figure permanently and fill the bath and every pan when an outage is forecast — which costs nothing and closes most of the gap.
Why this matters more on a well
On municipal water, pressure usually survives a local outage because the utility has its own backup and its own storage. You may get a boil notice; you rarely get nothing.
On a well, the pump is electric and the pressure tank holds minutes rather than hours. When the power goes, so does every tap in the house — no drinking water, no washing, and no flushing after the cistern refills once.
That is the difference between an inconvenience and a genuine problem, and it is why a rural property should treat water storage as a first purchase rather than an afterthought.
Tall buildings have a version of the same problem: booster pumps are electric, so upper floors lose pressure while lower floors keep it. The apartment page covers it.
What to store it in
- Purpose-made food-grade containers. Rectangular ones stack and store far better than round jugs, which matters more than any other feature because it decides whether you keep enough of them.
- Commercially bottled water, unopened, is the simplest option of all — no filling, no treatment, and a printed date.
- Not milk jugs. They are not designed for storage, the plastic degrades, and residual protein and sugar support bacterial growth however well you rinse them.
- Not containers that held anything else. Juice bottles and detergent containers are both bad ideas for opposite reasons.
- A larger drum if you have space and a way to move water from it. Fifty-five gallons is convenient to store and impossible to carry.
Where to keep it
- Cool and dark. Heat and light degrade plastic and encourage growth.
- Off a concrete floor if the container is plastic — conventional advice, and cheap to follow with a board or a pallet.
- Away from fuel, pesticides and solvents. Vapors can permeate plastic over time.
- Somewhere you can reach it in the dark, and somewhere you will not have to lift 58 lb down from a shelf.
- Split across two locations if you can. One flooded basement should not take the whole supply.
Rotation
Stored water does not spoil in the way food does, but containers and seals age and taste degrades. The practical routine:
- Label every container with the fill date in permanent marker.
- Replace tap-filled water every six months, at the same time you exercise the generator and test the alarms.
- Use the old water on the garden rather than pouring it away, and refill immediately rather than later.
- Follow the printed date on commercially bottled water, which is a quality date rather than a safety one.
Folding it into the same twice-a-year routine as the generator service is what makes it actually happen.
Free storage you already have
When an outage is forecast — which for a hurricane or a winter storm is usually a day or more — these cost nothing:
- Fill the bath. Not for drinking. A bath of water is a flushing reservoir, and a bucket into the bowl works with no pressure at all.
- Fill every pan, jug and bottle in the kitchen.
- Freeze water containers in the empty space in the freezer. They extend the 48-hour holding time and become drinking water as they thaw.
- Run the ice maker and bag the ice.
- Do the laundry and the dishes before it starts.
The forecast window is the biggest advantage a planned outage gives you, and water is the cheapest thing to do with it. The shutoff page makes the same argument for equipment.
Water heaters hold a lot
Worth knowing, and worth being careful with.
A conventional tank water heater holds 40 to 80 gallons, and that water is potable. It has a drain valve at the base intended for maintenance.
Three cautions if you plan to use it:
- Turn off the power or gas to the heater first. Draining a tank with the element still energized destroys it.
- Shut off the cold inlet so it does not refill with whatever is in the mains.
- Open a hot tap somewhere to let air in, or nothing will flow.
Sediment in the bottom of an older tank means the first water out is not pleasant. It is a reserve rather than a plan.
Treatment
If you are ever unsure about stored water — a container of unknown age, or a supply under a boil notice — the CDC and Ready.gov both publish emergency disinfection guidance covering boiling, unscented household bleach and commercial tablets.
We are not going to reproduce dosages here, because getting them slightly wrong matters and the authoritative versions are one click away and current. Both sources are linked below, and it is worth reading them before you need them rather than during.
