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There are two types of chemical treatment: those using iodine and those using chlorine. There are a variety of products on the market, so follow the directions on the bottle. Be advised that many of the tablets have an expiration date and become ineffective after that point. Also, once the bottle has been opened, the tablets must be used within a certain period. When in doubt, buy a new bottle. Remember that chemical purification methods may only be partially effective, depending on the water temperature.

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General treatment procedures

The effectiveness of all chemical treatment of water is related to the temperature, pH level, and clarity of the water. Cloudy water often requires higher concentrations of chemical to disinfect.

If the water is cloudy or filled with large particles, strain it, using a cloth, Millbank bag, etc, before treatment. Large particles, if swallowed, may be purified only "on the outside."

Add the chemical to the water and swish it around to aid in dissolving. Splash some of the water with the chemical onto the lid and the threads of the water bottle so that all water areas are treated.

The water should sit for at least 30 minutes after adding the chemical to allow purification to occur. If using tablets, let the water sit for 30 minutes after the tablet has dissolved.

The colder the water, the less effective the chemical is as a purifying agent.

It is best if water is at least 16 degrees Celsius before treating. You can place the water in the sun to warm it before treating.

Chemically treated water can be made to taste better by pouring it back and forth between containers, after it has been adequately treated. Other methods include adding a pinch of salt or adding flavourings after the chemical treatment period.

Iodine Treatment

Iodine is light sensitive and must always be stored in a dark bottle. It works best if the water is over 21 Celsius. Iodine has been shown to be more effect than chlorine-based treatments in inactivating Giardia cysts. Be aware that some people are allergic to iodine and cannot use it as a form of water purification. Persons with thyroid problems or on lithium, women over fifty, and pregnant women should consult their physician prior to using iodine for purification. Also, some people who are allergic to shellfish are also allergic to iodine. If someone cannot use iodine, use either a chlorine-based product or a non-iodine-based filter. Once the instructions have been followed,

let the treated water stand for 30 minutes before drinking. In order to destroy Giardia cysts, the drinking water must be at least 20 degrees Celsius. The water can be warmed in the sun before treating or hot water can be added. 

Always follow the manufacturer’s instructions for use.

Chlorine Treatment

Chlorine can be used for persons with iodine allergies or restrictions. Remember that water temperature, sediment level, and contact time are all elements in killing microorganisms in the water. Halazone is an example of a chlorine tablet product. To use, follow the manufacturer’s instructions.


Always have at least one backup method for water purification in case one fails. This can be any combination of methods. You can choose from the water filtration page or your own ideas. Don't forget that you can always boil the water. If boiling is your backup method, make sure you have enough fuel with you.

When using chemicals to treat the water, the taste may feel like you are drinking a swimming pool. Try adding flavoured vitamin C to iodized water, it completely eliminates any taste or colour of iodine. You must wait until the iodine has purified the water before adding the vitamin C. You can get many different types of flavouring, like orange and lemon powder used in military packs.

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