Clean drinking water is the single most important thing to secure in an emergency. If the tap runs dry or the supply is contaminated, here’s how to make water safe — ordered from most to least reliable.
Boiling (most reliable)
Bring water to a rolling boil and keep it there for at least one minute (three minutes at high altitude), then let it cool. Boiling kills the bacteria, viruses, and parasites that make you sick. It does not remove chemical contamination or sediment.
Filtration
A portable water filter with a small enough pore size removes bacteria and parasites, and many also reduce viruses. Follow the manufacturer’s instructions and replace cartridges on schedule. Filter cloudy water through a cloth first to keep the filter working longer.
Chemical treatment
Chlorine or iodine tablets — or plain unscented household bleach at the dose on the label — can disinfect clear water. Let it sit for the recommended time. Chemical treatment is less effective on murky water, so settle or filter it first.
Store what you can
The easiest water to “purify” is water you stored ahead of time. Keep about a gallon per person per day in clean, sealed containers, and rotate it every few months.
Go deeper
Water is chapter one of real preparedness. For a complete, calm reference — water, food, shelter, first aid, and every major emergency — see the Doomsday Survival Guide.