Water Purification – Boiling vs. Bleach vs. Iodine vs. Calcium Hypochlorite
All water sources are vulnerable to contaminants that can kill you or make you sick, so you better have a water purification plan. There are many ways to make water safe to drink, and they are not all equal.
Iodine: Iodine has been popular with outdoorsmen for decades because it can be made into tablets which makes it easy to store and carry, and makes getting the correct dosage simple (usually one tablet per quart of water). Iodine kills most, but not all, waterborne microorganisms. We don't recommend iodine for water treatment because it has a short shelf life, leaves a bad taste, many people are allergic, or develop an allergy to it, and it remains chemically active in your body, killing good cells and good bacteria that your body needs. If you use iodine, be aware that it is broken down by light, so store it accordingly.
Bleach: Household bleach has long been touted by survivalists and preppers as the water purification method of choice, and this is one of those, “close, but no cigar” moments. Liquid bleach is better than iodine because it becomes chemically inactive after it treats the water, breaking down into salt and water, and our bodies handle it quite well (even drinking straight household bleach is rarely fatal). The correct dosage is two drops of regular Clorox bleach per quart, or eight drops per gallon. Double the dosage if the water is cloudy. Like iodine, bleach kills most, but not all, waterborne microorganisms. The problem with bleach is its shelf life. Liquid bleach displays noticeable breakdown after just six months, and after about three years, a bottle of bleach breaks down completely to just salt and water. This brings us to Calcium Hypochlorite.
Calcium Hypochlorite: Calcium hypochlorite is a cheap and shelf stable chemical available at any pool and spa store and many hardware stores. When mixed with water, calcium hypochlorite becomes chlorine bleach. In fact, when you buy a jug of bleach at the store, you're getting calcium hypochlorite mixed with water in a 5.25% solution. By storing calcium hypochlorite you are basically storing super concentrated bleach without the shelf life problems. To make a bleach solution, mix 1/8 ounce (just under a teaspoon) of high-test granular calcium hypochlorite with one gallon of water. Use this at one part mixture to one hundred parts water to make your water potable. Just let it sit for a half hour before drinking.
Water Filters: High quality commercial water filters are a great way to make your water safe to drink because they are portable, fast (the water is ready to drink instantly), add no aftertaste, and they physically remove foreign particles from the water (chemicals may make that particle of feces harmless, but you're still drinking feces... yuck!). A good ceramic filter for use in North America and most of Europe will filter down to about 0.2 microns, and for reference, the period at the end of this sentence is about 600 microns in size. Finer filtration is needed in other parts of the world to remove viruses found in third world countries, but finer filters clog faster, so only use them if they are needed in your specific area.
A quick word on filters clogging: Some manufacturers claim their filters don't clog or that the filter can be back flushed indefinitely. This defies the laws of physics and has been proven false countless times. If a company will lie to you about something as silly as that, you can bet the bank their claimed micron filtration number and other claims are false as well. Sawyer water filters are notorious for this, but shop carefully because they aren't the only one.
Boiling: Each of the methods mentioned above kill, remove, or deactivate most, but not all, waterborne contaminants. Boiling is the only method of ensuring that water is totally free from biological hazards. Contrary to popular belief, you don't need to boil the water for several minutes. Even at high altitudes, water is safe to drink the moment it begins to boil, so don't waste fuel boiling it any longer. Actually, it's safe a while before the water boils, but boiling is a good standard to make sure the proper temperature has been reached. To reduce the amount of fuel needed for everyday water purification, we use a Sun Oven when it's sunny, and an EcoZoom Rocket Stove when it's not. Of course, while safe to drink, the water will still have undesirable particles in it so we recommend filtering the boiled water before consumption.
Iodine- Poor: Bad taste, allergies, short shelf life, remains active in body.
Household Bleach- Poor: Short shelf life, mild taste.
Calcium Hypochlorite- Good: Indefinite shelf life, mild taste, multiple uses as a cleaner.
Filters- Good: Long useful life, no added taste, physically removes contaminants.
Boiling- Good: Kills all biological contaminants, must allow to cool before drinking, removes no particles.
Combination of Boiling and Filtering- Excellent: Pure water that is both safe to drink and free from undesirable particles.