How to Purify Water

When the water you're hoping to drink might be riddled with parasites, bacteria, or toxic metals, you can't afford to skimp on water purification. In the very circumstances that put you in contact with questionable water (being in the wilderness, surviving or recovering from a disaster, or living in a part of the world where water isn't purified for you) the last thing you want to do is to get sick. Read the following instructions carefully and always be prepared to purify water yourself.

Steps

Clean the containers in which you're going to hold or store the water. Use dish soap and water. Rinse thoroughly. After washing them, submerge them in a solution of 1 teaspoon of non-scented liquid household chlorine bleach to every quart of water (making sure the entire surface of the bottle comes in contact with the solution) then rinse thoroughly with a weaker mixture of bleach and water.[1]
- Don't use any container that has had milk or fruit juice in it. Milk protein and fruit sugars remain in the container and can fuel bacterial growth when water is stored. Plastic soda bottles are suitable.
Filter water through a clean cloth. Then allow it to settle for at least 30 minutes and pour off the clear water for purifying. This process of filtering and settling is especially important if you're going to be using chemical purification because disinfectants are less effective in cloudy, murky, or colored water.[2]
- You can use cotton cloth, such as a clean handkerchief or clean white sock, or silk (water passes quickly through multiple layers).
- One way to set this up is to cut the bottom off of a water or coke bottle. Roll a clean sock up on itself and stuff it down to the neck of the bottle. Pour your water through the filter until it is clear to the eye.
- One way to speed up clearing of water is to add a little alum (Aluminium Sulfate). This causes impurities to coagulate which are removed as the particulate settles to the bottom of the container.
Purify the water using any of the following methods. If you can, combine boiling with a chemical disinfection method; the boiling is more thorough, but the chemical method will continue to keep the water safe when it's stored.[3]
- Boiling kills most types of disease-causing organisms and is the most recommended purification technique. Boil the water for at least one minute, then let it cool. Make sure it's a full, rolling boil. If you are more than one mile above sea level, boil for three minutes.[4]
- Disinfecting with household bleach kills some, but not all, types of disease-causing organisms. The bleach must contain chlorine in order to work. Do not use scented bleaches, color-safe bleaches, or bleaches with added cleaners. Most household chlorine bleaches have 4-6% available chlorine, in which case you should add 1/8 teaspoon (8 drops) of regular, unscented, liquid household bleach for each gallon of water (2 drops per Liter), stir it well and let it stand for 30 minutes before you use it. Check the label; if the percentage of available chlorine is around 1%, or you don't know what the percentage is, use 40 drops per gallon or 10 drops per Liter; if the percentage is 7-10%, use 4 drops per gallon or 1 drop per Liter. Double the amount of chlorine if the water is cloudy, murky, or colored, or if the water is extremely cold. If after sitting covered for 30 minutes the water doesn't have a slight chlorine odor, repeat the dosage and let sit for another 15 minutes.[5]
- Granular calcium hypochlorite works in the same way as household bleach. You can dissolve one heaping teaspoon of high-test granular calcium hypochlorite (about 1/4 ounce) in two gallons of water (5 milliters or 7 grams in 7.5 liters of water) to make a disinfecting solution. Then add one part of the disinfecting solution to each 100 parts of water to purify.[6]
- Potassium Permanganate can be used to disinfect water, it can be purchased from camping supply stores and pool treatment stores.
- Disinfecting with iodine is generally less effective than chlorine in controlling the parasite Giardia, but it's better than no treatment at all. Add 5 drops of 2% iodine (from the medicine chest or first aid kit) to every quart or liter of clear water; add 10 drops if the water is cloudy. Let the solution stand for at least 30 minutes.[7]
- For commercially prepared chlorine or iodine tablets, follow the instructions that come with them. If you don't have instructions, use one tablet for each quart or liter of water to be purified.[8]
- (SODIS method) Pouring the water into clear plastic PET bottles, and exposing to direct sunlight for at least 6 hours, has been shown to be an effective method of disinfecting.[9]
To improve the flavor of purified water (boiled water can taste "flat", and disinfected water can have a strong chlorine taste) aerate it by pouring it from one clean container to another several times. Alternatively, add a pinch of salt to each quart or liter of water.[10] If the flavor is still unpleasant, use a powdered drink mix, if available.
Close the container carefully. Don't touch the inside or the rim with you fingers, or else the water could become contaminated. If you're going to drink some, but not all of the water, don't drink directly from the container. Pour it into another container and drink from that. Contact with your lips and mouth can contaminate water that's going to be stored. If you don't drink the water immediately, write the date on the bottle. Store it in a cool, dark place for up to six months.

Tips

Both bleach and iodine work much better in warm water.[11]
A person needs at least a half gallon of water per day to survive, sometimes more (children, nursing mothers, people who are ill, and when the weather is hot, everyone).[1]
Use purified water for brushing your teeth.
Water that's collected through condensation (such as from plants or soil) needs to be purified. The process of condensation leaves some sediments behind, but unless boiling temperature is reached, parasites and other harmful substances may still be in the water.

Warnings

Commercial filters made for tap water may only remove basic minerals to make it taste better, depending on the quality of the particular filter. They may not remove parasites or other threats that are removed through in water treatment facilities. Check the label to be sure what you're getting.
People with thyroid problems should check with their doctors before using water treated with iodine.
Quality reverse osmosis filter systems remove impurities down to several hundred thousandths of a micron - small enough to remove all organic matter (and other matter such as chlorine as well).

Sources and Citations

Choosing water supply and purification methods at Appropedia.org - includes a focus on appropriate technology and less developed countries.

Article provided by wikiHow, a collaborative writing project to build the world's largest, highest quality how-to manual. Please edit this article and find author credits at the original wikiHow article on How to Purify Water. All content on wikiHow can be shared under a Creative Commons license.

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