Emergency Water Calculator
| Household | 3 days | 7 days | 14 days |
|---|---|---|---|
| 1 person | 3 gal | 7 gal | 14 gal |
| 2 people | 6 gal | 14 gal | 28 gal |
| 4 people | 12 gal | 28 gal | 56 gal |
| 6 people | 18 gal | 42 gal | 84 gal |
Emergency water follows one federal rule and one arithmetic: store at least one gallon per person per day, because drinking takes about three quarters of a gallon and the rest goes to cooking and basic hygiene. Ready.gov adds a horizon worth stretching for: a three-day supply is the minimum kit standard, but a two-week supply is the practical target if you have the space - and two weeks for a family of four is 56 gallons, which sounds enormous until you see it as twelve 5-gallon jugs and a case or two of bottles.
Bottom line: a family of four should hold 12 gallons minimum (three days), 28 gallons for the week, and 56 for the two-week target - roughly eleven 5-gallon jugs. Two free reserves most homes already own: the water heater, which holds 30 to 50 gallons of potable water behind its drain valve, and the freezer-to-cooler trick of freezing jugs that keep food cold first and drink later. Count what you have before you buy; most kitchens are a third stocked already.
The honest part: tap-filled containers should be replaced every six months per Ready.gov, stored cool and dark and off concrete; commercially bottled water carries a best-by date but the water itself keeps. Disinfecting storage containers takes a teaspoon of unscented household bleach per quart of water, swished and rinsed; treating found water means a rolling boil for one full minute. This page links Ready.gov directly because the numbers above are theirs - the container math is the only part we derived.
How to use
- Count people and pets, then pick the horizon: three days minimum, seven practical, fourteen if the storage space exists.
- Buy or fill to the gallon total - mixed formats work best: cases of bottles for portability, 5-gallon jugs for the main mass, and the water heater counted as reserve.
- Label fill dates on anything from the tap, store cool and dark, and set a six-month phone reminder to rotate; sanitize reused containers with a teaspoon of unscented bleach per quart of water.
Frequently asked questions
How much water should I store for a family of four?
Twelve gallons covers the three-day kit standard, 28 gallons covers a week, and the two-week target is 56 gallons - one gallon per person per day, per Ready.gov. Practically: eleven 5-gallon jugs hold the two-week supply, and the water heater behind its drain valve adds a hidden 30 to 50 gallons most households never count. Pets add roughly half a gallon each per day at the planning stage; an 80-pound dog drinks close to a human.
Is the water in my water heater safe to drink?
Yes - tank-style water heaters hold potable water, and in a shutdown the drain valve at the bottom is a 30 to 50 gallon reserve. Cut power or gas to the tank first, let it cool, open a hot-water tap upstairs to break the vacuum, and drain from the bottom valve; if the tank is old or the manual warns against it, treat before drinking. Tankless units hold nothing, and the toilet tank is the reserve of last resort - the bowl is not the tank, and only the tank counts, and only if no chemical cleaner sits in it.
How do I treat water if the stored supply runs out?
Boiling is the safest method: a rolling boil for one full minute kills everything that matters, then rest and pour through a coffee filter or clean cloth for sediment - Ready.gov treats it as the default. Unscented household bleach works when you cannot boil, following the label for the concentration; sanitize storage containers with a teaspoon of bleach per quart of water and rinse. Pool and spa water is not drinking water, full stop - the chemicals that keep a pool clean are not the dose a body wants.
Can I just freeze water jugs instead of storing them?
Freezing works with one physics caveat: water expands about nine percent, so every jug freezes with two inches of headspace or it splits. The bonus is real - frozen jugs keep the freezer cold through a multi-day outage and become drinking water as they melt, a two-for-one no purchased case matches. Freeze in food-grade jugs, lay them flat for faster thaw access, and rotate them into the sink every six months like any tap-filled container.