10 Best Ways to Purify Water for Drinking


boiling kettle on campfire

The first method in learning how to filter water is by boiling it. The US Environmental Protection Agency says you must bring water to boil and keep it boiling for at least a minute for it to be purified.

The higher the altitude, the longer you should keep it boiling. For instance, in altitudes above 5000 ft, you should keep it boiling for 3 minutes.

Boiling is one of the easiest and safest ways to purify water. It’s also the least expensive and one you can do even when you’re down to the barest resources. Boiling can kill bacteria, parasites and other harmful microorganisms in the water. If you suspect contamination of your local water source, boil it first before consuming it.


Filters work by physically straining the water to remove various impurities. If the water looks cloudy, filtering can be done before boiling to take the debris out of it. While filtering can get floaties, bacteria and some parasites out of the water, it doesn’t do much for viruses. They can also be bulky and more expensive than other means of purification. The upside is once water is filtered, you can drink it right away.

DIY Biofilters

In cases of emergency, you can make your own biofilter to purify water. Biofilters usually involve the use of gravel, sand and activated charcoal. The idea is to let water pass through these natural filters to strain bacteria, parasites and other nasties — the lower it goes, the finer the strain becomes, the cleaner your water would be. These filters can be big enough to produce gallons of water in a day, like this one; or it could be a handy biofilter made of PVC pipes, like this.

Survival Straws

Commercial filters like survival straws are pretty popular because they’re handy when you’re on the trail or in survival situations. They’re light and portable so you can keep them in your emergency kit or bag and they enable you to drink directly from the source. Survival straws like LifeStraw claim to get rid of 99.99% of contaminants, including E. Coli and Giardia. They don’t work with saltwater though, so only use it on freshwater sources.

Solar Disinfection

You can’t discount the power of the sun when it comes to purifying water. Solar water disinfection (SODIS) works by exposing a clear bottle of water in direct sunlight for 12-24 hours. For cloudy days, the water bottle is exposed for 48 hours. This harnesses the power of the sun and natural UV rays to kill bacteria. You obviously can’t use this method when it’s raining (you can catch rainwater instead, though), but this could very well save you from dehydration in cases where you’re exposed to a lot of sun.

Handheld UV Devices

If you can’t use UV from the atmosphere, you might be better off by keeping the UV in your pocket. Hand-held UV devices are available and can effectively treat water by “zapping” the microorganisms in the water. The device is light, the treatment is quick (all done in about 2 minutes) and it leaves no aftertaste to the water. The downside is it’s battery-powered and is pretty pricey.

Chemical treatment

Iodine and chlorine are used to treat water and make it safe for drinking. These are very handy; they come in portable bottle or tablet forms that you can carry around your kit so they’re ideal in survival situations. They also don’t need any special procedures or fuel to treat the water.


Iodine has great disinfecting properties: you can use it to dress minor injuries and to purify water. Iodine comes in tablet and tincture form. The downside to using iodine is that you have to wait for at least 30 minutes before you can consume the water. It also leaves a nasty aftertaste, so it’s handy to carry around vitamin C tablets or a powdered juice mix to help with the taste. Pregnant women and people allergic to shellfish would have to stay away from this method, though.

With the 2% tincture, you can use 5 drops of iodine for every quart of water. It should sit for about 30 minutes before you can drink it; longer if the water is cloudy.

For tablets, you can use 1 or 2 tablets for every quart. You have to wait for the tablets to dissolve and again, wait for 30 minutes for it to kill all the nasties.


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If you’ve got restrictions to iodine, you can use chlorine tablets instead. They work pretty much the same way as iodine tablets. You can use one or two tablets of chlorine to treat your water, wait for it to dissolve and let it sit for about 30 minutes. Water treated with chlorine will have a longer shelf life. You can also get rid of the aftertaste and smell by letting it sit uncovered for a few minutes so the chlorine can evaporate.

Household bleach

Household bleach contains chlorine, so you can also use it to disinfect your water. But you have to be careful: only use regular, unscented bleach that has been stored for less than a year. Don’t use bleach with additives like perfumes, additional active ingredients, and color-safe properties. 6 drops of household bleach can pretty much do the trick to a gallon of water. Let it sit for 30 minutes.

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