Emergency Water Storage: How Much to Store and How to Make Any Water Safe

Use one gallon per person per day as the floor. One person needs 14 gallons for two weeks, 30 for a month and 90 for three months. A family of four needs 56, 120 and 360. Add a gallon a day for a large dog. In a hot climate, or if anyone is pregnant, nursing or sick, plan on more.

Store what you can and plan to treat the rest. Commercially bottled water keeps until its date. Ready.gov says to replace water you bottle yourself every six months. Keep containers in a cool, dark place off bare concrete, away from gasoline, pesticides and anything with fumes.

Your home already holds water you can use. A typical tank water heater holds 40 to 50 gallons. Turn off its power or gas first, then drain it from the valve at the bottom. The pipes hold a few more gallons, and ice in the freezer counts as well. If you get a warning, fill the bathtub with a bladder made for drinking water while the taps still run.

Microfilters like the Sawyer (0.1 micron) and the Katadyn Hiker Pro (0.2 micron) catch bacteria and protozoa such as Giardia and Cryptosporidium, plus sediment. Neither listing claims to remove viruses, and viruses are the bigger risk in water near people or sewage. So filter first to clear the water, then disinfect.

The CDC's emergency steps are simple. Boiling is the most reliable: bring clear water to a rolling boil for one minute, or three minutes above 6,500 feet. Without fuel to spare, use unscented household bleach. EPA's guidance is 8 drops of 6% bleach or 6 drops of 8.25% bleach per gallon of clear water. Stir, wait 30 minutes, and double the dose if the water is cloudy or very cold. Chlorine tablets like Aquatabs do the same job in a measured dose. Bleach loses strength over time, so buy a fresh jug every year.

None of this removes chemicals, fuel or heavy metals. Never drink from a source that may be contaminated by fuel, industrial runoff or floodwater from a chemical site. Rain from a clean roof, a private well or a spring is a much better start than a ditch.

For the first 72 hours, keep a few cases of bottled water or a filled jug per person. For two weeks, store one gallon per person per day in sealed jugs or a drum, plus a bathtub bladder to fill on a warning. Beyond that, the plan becomes collection and treatment: a gravity bucket with a Sawyer filter inline, chlorine tablets or bleach, and a source such as rain barrels, a well with backup power or a nearby spring.

If you are on a well, the pump is the weak link. A 1/2 HP well pump draws about 1,000 W and needs 240 V on most homes, so it needs a generator or a large home battery. Our generator for a well pump guide sizes one, and our solar power for a long grid-down guide covers keeping a battery charged when fuel is gone.