Emergency Water: How Much to Store, How to Keep It, How to Make It Safe

Store at least a gallon per person per day, keep it clean and dated, and know how to boil, disinfect, or filter water if your supply runs out.

Clean water is a top priority in an emergency.^[2] Start with 3 days of water and build up to 2 weeks.^[1] This guide covers how much to keep, how to store it so it stays clean, and what to do if you have to make questionable water safe to drink.

How much water you actually need

Plan on at least 1 gallon per person per day. That covers drinking plus cooking and washing up.^[1][2] A normally active person drinks about half a gallon of that.^[2]

• Plan for more if you live somewhere hot, or if you have children, someone nursing, or someone sick in the house. They all need extra.^[2]
• Pets count too. Put drinking water and bowls in their kit.^[6]
• Two targets: 3 days of water you can grab if you have to leave, and 2 weeks of water at home.^[1]
• If water gets low, don't ration it. Drink what you need today and look for more tomorrow. Staying cool and moving less lowers how much your body needs.^[2]

Storing water so it stays clean

Store-bought bottled water is the simplest and most reliable choice. Leave it sealed in its original bottle and go by the use-by date printed on it.^[2]

Filling your own containers works fine if you do it carefully:

• Containers: buy food-grade water containers, meaning containers made to hold drinking water. Clean 2-liter soda bottles also work. Don't reuse milk or juice jugs, because leftover milk protein and sugar can't be fully washed out and germs grow on them. Skip glass too, because it's heavy and breaks.^[2]
• Clean and sanitize: wash with dish soap and water, then swish a mix of 1 teaspoon of unscented bleach in 1 quart of water around the inside. Rinse well.^[2]
• Fill: use regular tap water. If your water company adds chlorine, you don't need to add anything. If your water comes from a well or another untreated source, add 2 drops of unscented bleach per gallon.^[2]
• Label and store: cap it without touching the inside of the lid, write the fill date on it, and keep it somewhere cool and dark.^[2] If your area floods, keep it up high.^[5]
• Replace home-filled water every 6 months.^[2] If any bottled water smells off, don't drink it.^[5]

Making water safe: boiling and bleach

If water looks cloudy, let it settle first, then pour it through a clean cloth, paper towel, or coffee filter.^[3] Use treated water for drinking, cooking, making drinks, washing dishes, and brushing teeth.^[3]

• Boiling (best option): bring it to a rolling boil for at least 1 minute (3 minutes above 5,000 feet). Let it cool, then store it in clean covered containers.^[3] If it tastes flat, pour it back and forth between two clean containers a few times.^[3]
• Bleach (if you can't boil): use plain, unscented bleach labeled for disinfecting, from a bottle stored at room temperature for less than a year.^[3] Check the label for strength (6% or 8.25%):
  • 1 quart: 2 drops of either strength
  • 1 gallon: 8 drops of 6%, or 6 drops of 8.25%
  • 2 gallons: 16 drops (1/4 teaspoon) of 6%, or 12 drops (1/8 teaspoon) of 8.25%^[3]
• Double the bleach if the water is cloudy, colored, or very cold. Stir, wait 30 minutes, and sniff. You should smell a little chlorine. If you don't, add the same dose again and wait 15 more minutes.^[3]
• Water treatment tablets also work. Follow the package directions, because strengths vary.^[3]

Filters: what they catch and what they miss

A water filter is basically a screen full of tiny holes. The smaller the holes, the more it catches. Hole size is measured in microns, which are millionths of a meter.^[4]

• Check for an "absolute" rating. That number is the biggest hole in the filter. A "nominal" rating is just the average, which tells you less.^[4]
• An absolute 1-micron filter, or one labeled for cyst removal, catches Cryptosporidium, a common stomach parasite.^[4]
• Bacteria are smaller (about 0.2 to 4 microns), and viruses are far smaller (0.004 to 0.1 microns). Only a few filter types, like ultrafilters and reverse osmosis units, have holes small enough to block all viruses. Disinfecting kills viruses.^[4]
• Carbon filters (the kind in most pitchers) improve taste, and many reduce lead. On their own, they aren't designed to remove all germs.^[4]
• Filters wear out. They clog after a set amount of water, so replace cartridges on the maker's schedule.^[4]

No single method does everything, and combining methods often works best.^[2] A practical setup: filter out the dirt, then boil or disinfect to kill germs.

Water already hiding in your home

Your water heater tank, your pipes, and the ice in your freezer all hold usable water.^[2][3] As ice melts, it gives you drinking water.^[5]

• Water heater: turn off the electricity or gas first. Then open the drain at the bottom of the tank, and get the water flowing by closing the water intake valve at the tank and turning on a hot-water faucet. Refill the tank before you turn the power or gas back on. If the gas gets shut off, you'll need a professional to turn it back on.^[2]
• Pipes: turn on the highest faucet in the house to let air in, then collect water from the lowest faucet.^[2]
• Protect it: if you hear about broken water or sewage lines, close your main water valve so dirty water can't get into your pipes. Make sure everyone at home knows where that valve is.^[2]
• Don't drink from toilet tanks or bowls, radiators, waterbeds, or pools and hot tubs.^[2]

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