How to sterilize water? Simple:

You don't need to ‘sterilize’ water. Sterilization is the destruction of all microorganisms in, on and around an object. What is needed, is disinfection (killing of pathogenic (disease causing) organisms).

Disinfection can be done many ways, including filtration, heat, ozonation, and chemical disinfection.

Despite many stories to the contrary, simply boiling water will disinfect it. At any elevation you're likely be at the boiling point of water is high enough to kill (or denature) anything in the water. You don't need to boil it for any particular length of time, just get it boiling at a good rolling boil.

Filtration is a good method, you should use a filter that has an absolute rating of 0.2 micron diameter or LESS (0.1 micron). Personally, I use iodine crystals (Polar Pure ™ first, then filter the water.

Chemical disinfection is the use of various chemicals (usually a halide like chlorine or iodine) in the water. It's usually a quick, economical and effective method.

Here is a summary of water disinfection chemical usage based on the Wilderness Medical Society Practice Guidelines 2nd Edition, edited by William Forgey MD (page 63):

For chemical disinfection, the key is the concentration of halogen, in parts per million (halogen to water):

Concentration of Halogen
Contact time Contact time Contact time
@ 5oC / 41o F @ 15o C / 59o F @ 30o C / 86o F

2 ppm 240 minutes 180 minutes 60 minutes
4 ppm 180 min 60 min 45 min
8 ppm 60 min 30 min 15 min

How to get the desired concentration of halogens, for various products:

Iodine tablets, also known as:
tetraglycine hydroperiodide; EDWGT (emergency drinking water germicidal tablets); USGI water purification tablets; Potable Aqua (trade name); Globaline (trade name):

4 ppm – ½ tablet per liter of water 8 ppm – 1 tablet per liter of water.


NOTE: These tablets should be gunmetal gray in color when used –
if rust colored, they are useless:

The free iodine has combined with atmospheric moisture. The bottles should be kept well sealed and replaced often. Checking the tablets in the bottle just exposes them to moisture in the air.


For 2% iodine (tincture of Iodine) (gtts=drops)
4 ppm – 0.2 ml (5 gtts) 8 ppm – 0.4 ml (10 gtts)

NOTE: Tincture of Iodine should NOT be used as a wound treatment, so this is not a good option for a 'dual use' item.

10% povidone-iodine solution (Betadine ™)

NOTE: Solution only, NOT SCRUB - Scrub has soap in it

4 ppm - 0.35 ml (8 gtts) 8 ppm – 0.7ml (16 gtts)

Saturated (in water) Iodine crystals (Polar Pure ™)
4 ppm – 13 ml 8 ppm – 26 ml

Iodine crystals in alcohol
0.1 ml / 5 ppm 0.2 ml / 10 ppm

Halazone tablets (Monodichloroaminobenzoic acid)

4 ppm – 2 tabs 8 ppm – 4 tabs

NOTE: The old Vietnam era chlorine tabs are decades out of date. Chlorine tabs decay even more rapidly than iodine tabs. Not recommended.

Household bleach (Chlorox ™)

4 ppm – 0.1 ml (2 gtts) 8 ppm – 0.2 ml (4 gtts)

Note: Plain chlorine bleach offers a relatively economical method of treating large (gallons) of water at a time. 4 liters is approximately 1 gallon.

For very cold water contact time should be increased.

If drinking this water after disinfection, flavoring agents (drink mixes, etc) can be added: This must be done AFTER the period allocated for disinfection (the disinfecting agent will bind to the organic material and not work).

Liquid chlorine bleach has a relatively short shelf life - less than 6 months from the time the jug is opened.

To be able to have a 5% chlorine solution (for water or other disinfection) it's possible to make your own 5% (more or less) hypochlorite solution.

Chlorine bleach (Chlorox, Javix for our Canadian friends) is 5% (more or less) sodium hypochlorite. We don't care one way or the other about the sodium part in it, all thats important is the hypochlorite. Thats what does the disinfection.

Pool shock chlorine is available in dry form, from many locations - pool supply stores, the grocery store (maybe), etc. It usually comes in 1 lb plastic bags, and is around 75% calcium hypochlorite. It's pretty inexpensive, too - a few dollars a bag. Like before, we don't care one way or the other about the calcium part of it.

If you take about 75 grams (two ounces by volume) of your typical pool shock chlorine (calcium hypochlorite) and mix it with a liter (quart) of water, you will have a mixture that is about 5% hypochlorite. You can use this like you would use Chlorox bleach, further dilute it for disinfection or water sterilization, even bleach your white clothes with it. If you have a precision-enough kitchen scale that can weigh out the 75 grams (1157 grains, or 2.6 ounces) weigh it out, otherwise an 1/8 cup dry measure measuring cup plus 2 tablespoons should be close enough.

The mixed solution will suffer from degradation the same way that regular bleach will. The dry powder is pretty stable (it will lose 3-5% per year) but if kept cool, dry, and sealed it should stay potent for quite awhile. Keep it sealed in non-corrosive (plastic) containers and bags, and expect to have to replace the containers from time to time: Bleach is a very potent oxidizer and attacks a LOT of stuff.

Other than field expediency why so complex?
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http://www.campmor.com/outdoor/gear/Product___80877

What happens if you run out of all that stuff?

What happens if you need to sanitize more than a quart of water at a time?

A pound of pool shock costs me around $7. It will make 453/75 or 6 quarts of bleach solution, which will purify a lot of water at 4 drops per quart.

Say you have (or found) a water buffalo. 400 gallons, how are you going to insure the water in it is potable? Just because you filled it with tap water doesn't mean it will stay clean.

(By the way, to test water, buy a pool test kit (or at least the orthotolidine or OTO in one), and get a sample of water in a clear glass. Put a drop of the OTO in the water, it should turn yellow. If it doesn't, no chlorine).

That Pur kit is good for 7.5 gallons of water and costs the same as 2 lbs of pool shock. My filter cartridge is only good for 200 gallons and costs as much to replace as 6 bags of pool shock.

And, since regular liquid bleach will deteriorate rapidly, it might be a good idea to have a method that will last longer.

"Say you have (or found) a water buffalo. 400 gallons, how are you going to insure the water in it is potable? Just because you filled it with tap water doesn't mean it will stay clean."

start a fire under it and bring it to a boil..

seriously if one want to treat a 55 gal barrel of rain water how many pool tablets would it take?

We're not talking about pool tablets, we're talking about making a bleach solution, out of pool shock chlorine (powder). They're not the same.

And a 55 gallon barrel has 220 quarts so it would take 880 drops of bleach (if it's not too dirty) or twice that if it is. 880 drops is about 440 ml so a coke size can will do.

Water Supply Video

Water Purification How to Video - Build your own fitler kit

Here;s another link that shows you how to build a homemade Berky water filter.

Simple and effective...

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