Water when the taps fail

When stored water runs out

Our water storage guide covers keeping a supply on hand. This guide is for when that supply is gone, or the outage lasts longer than anyone planned, and you have to make drinking water from whatever you can find.

Water from outside can carry three kinds of danger: germs (bacteria, viruses and parasites such as Giardia and Cryptosporidium), dirt and sediment, and chemicals such as fuel, pesticides and heavy metals. No single method handles all three, so the safe approach works in steps: clear it, filter it, then disinfect it.

Finding water

• Start inside the home: the water heater tank, pipes, ice cubes and the toilet tank (not the bowl), as covered in our water storage guide.
• Rainwater from a roof or a tarp, as described below.
• Springs, streams, rivers, lakes and ponds. Moving water is usually better than still water, and clear is better than cloudy.
• Snow and ice. Melt it first, because eating snow chills the body, then treat it like any other outdoor water.
• Swimming pools and hot tubs. Use this water for flushing and washing. Pool chemicals make it a poor choice for drinking.

Collecting rainwater

Rain is often the cleanest water you can get, but it picks up bird droppings, dust and debris on its way off a roof.

• Run a downspout into a clean, food-grade barrel with a lid or screen to keep out insects and leaves.
• Let the first few minutes of each rainfall run to waste. That first flush carries most of the dirt off the roof.
• A tarp strung at an angle over a bucket collects a surprising amount in a heavy rain.
• Treat collected rainwater before drinking it, the same as any outdoor water.
• Check local rules: a few places limit rain collection.

Step 1: clear the water

Cloudy water shields germs from disinfection and clogs filters fast. Clear it first.

• Let it stand: fill a container, let the sediment settle for a few hours or overnight, then pour off the clear water on top without stirring up the bottom.
• Strain it through a clean cloth, a coffee filter or several layers of a T-shirt.
• A homemade layered filter of gravel, sand and charcoal in a bucket or bottle makes water clearer. It does not make it safe. Always disinfect afterward.

Step 2: filter

A good portable filter removes parasites and bacteria quickly with no fuel. It is the best tool for turning a lot of outdoor water into drinking water, but read the label: not every filter removes everything.

• For Giardia and Cryptosporidium, the CDC advises a filter with an absolute pore size of 1 micron or smaller.
• For bacteria, look for a filter rated around 0.1 to 0.2 micron. Most hollow-fiber squeeze and gravity filters are.
• Most filters do not remove viruses. Disinfect filtered water as well if it may carry sewage or human waste, which is common after disasters.
• Gravity bucket filters with ceramic or carbon elements can supply a whole family. Learn how to clean or back-flush the element before you need to.
• Don't let hollow-fiber filters freeze: ice can crack the fibers with no visible damage.
• Activated carbon improves taste and removes some chemicals, but it does not reliably remove germs on its own.

Step 3: kill the germs

Disinfection is the step that makes water safe to drink. Use one of these methods.

• Boiling is the most reliable. Bring clear water to a rolling boil for 1 minute (3 minutes above 6,500 feet), then let it cool covered.
• Unscented household bleach: following EPA guidance, add 8 drops of 6 percent bleach or 6 drops of 8.25 percent bleach per gallon of clear water. Double it for cloudy, colored or very cold water. Stir and wait 30 minutes. It should smell faintly of chlorine; if not, repeat the dose and wait another 15 minutes.
• Chlorine dioxide tablets work against Cryptosporidium, which ordinary chlorine handles poorly, but may need up to 4 hours. Follow the package directions.
• Iodine tablets kill most germs but not Cryptosporidium, and shouldn't be used by anyone pregnant or with a thyroid condition.
• Sunlight (SODIS): fill clear plastic PET bottles of 2 liters or less with clear water and lay them on their sides in full sun for 6 hours, or 2 full days if it's cloudy. It doesn't work with cloudy water or in steady rain.

Chemicals, salt and distillation

Only distillation removes salt, heavy metals and most chemicals. Distilling means boiling water and catching the steam as it turns back into water, leaving the contaminants behind.

• A pot with its lid upside down, and a cup set on a stand in the middle of the pot, catches slow drips of distilled water from the lid's handle. It takes a lot of fuel for a little water.
• A solar still, a plastic sheet over a hole with a cup in the middle, produces very little, usually far less than a person needs in a day. Treat it as a last resort, not a plan.
• If you suspect chemical contamination and can't distill, find another source.

Storing and using treated water

• Keep treated water in clean, covered containers. Pour it out; don't dip hands or cups into it.
• Use separate, clearly marked containers for raw water and treated water.
• Use untreated water for flushing and cleaning. Use treated water for drinking, cooking, brushing teeth, washing dishes and making baby formula.
• Wash hands with soap after handling raw water and before touching food.
• Watch for signs of waterborne illness: diarrhea, cramps, vomiting and fever. Keep oral rehydration salts on hand, and get medical help for anyone who can't keep fluids down.