Using Chlorine Bleach to Disinfect Water

December 15, 2011

Recommended Purchases, Skills, Water

using chlorine to purify pond water

As Joe has noted several times in previous posts, the human body does not last long without water.  So much of our body is composed of it and it facilitates so many biological processes that we must have a pretty steady and generous supply of it for good health.

Storing and Collecting Water

Storing a sufficient supply of purified water is an excellent idea although it is quite a space hog. Additionally, there’s no guarantee that you’ll be able to store enough for your needs over an extended period of time.

Second to storing clean water would be having a dependable source for it.  Collecting rainwater is a good idea, but obviously dependent on precipitation that may be long in coming during hot summer months.

We are blessed with several ponds on our property.  They give us some peace of mind regarding our water situation.  Three of the four are located on low spots on our land, so they pretty easily refill with rainfall.  (By the way, one of them was man-made and did not hold water for the first several years we lived here.  Eventually, our herd of cows effectively compacted the bottom and sides by their weight as they waded in and out during hot weather and it now holds water year round.  I have heard hogs will do the same thing).

It’s really nice to have these water sources for ourselves and our animals, but we cannot just drink it as is. We must make it potable for human consumption.  We would first choose from the ponds the animals do not have access to.  Next, we would filter it (more on that another time).  Lastly, we would disinfect it.  This is where the bleach comes in.

Joe mentioned in his recent piece on fire that boiling water will effectively kill microbes lurking within.  Keeping enough safe water for everyone to drink could become someone’s all day job if done exclusively by fire, plus you have to wait for it to cool.  An alternative is to use household bleach.

Storing bottles of prepared bleach is a good idea.  Unfortunately, it loses its potency over time, even if the seal is unbroken.  This is especially true in warm temperatures.  What we have decided to do is to also store powdered calcium hypochlorite (concentrated bleach granules) for use in making chlorine bleach as we need it.

Where can you get powdered bleach?

We ordered pool shock in 1 lb packets and have stored them ina  “gamma seal” lidded bucket.  It is important that you make sure of what you are getting.  You do not want an algaecide or other chemicals mixed in with the calcium hypochlorite-  those are not safe for human consumption.

How do I use it?

Adding 1/8 oz  (about 3/4 teaspoon) of the 65% available chlorine powder to a gallon of water will create full strength bleach.  This bleach can then be used at a rate of about 8-16 drops of bleach added to each gallon of collected water.  At this level of usage, each pound of powdered chlorine will produce approximately 128 gallons of prepared bleach, which will in turn purify thousands of gallons of water.  What a Godsend you could be to your family and neighbors in preventing water-borne disease!

It is important to note that cloudy or off-smelling water should get additional drops of bleach.  Shake it well and then wait 30 minutes for the microbes to die.  While it is considered safe to drink the water after the half hour is up, the smell and taste will usually dissipate overnight if it is left to stand uncovered.

When purifying water in a container that you will drink out of later, such as a bottle or jug, be sure to allow some of the chlorinated water to cover the rim. The easiest way to do this is to loosely put the cap on the bottle and shake it. This will allow some of the contained water to splash out on to the rim. You can then tighten it. This will kill the microbes on the surface of the rim so won’t accidentally consume contaminated water.

Chlorine is generally considered a better option than iodine since iodine does not break down chemically and often has a strong unpleasant taste.

Please take care to identify any containers you fill with bleach.  Since you may not have much choice in what you can store the prepared bleach in (even old water bottles), you need to be careful that no one accidentally splashes it in their eyes or tries to drink it full strength.

UPDATE:  Just to clarify-  If possible, always filter and boil questionable water rather than relying on chlorine bleach if you have that choice.  You never want to introduce unnecessary chemicals into your body.  In addition to the debate about whether Giardia can be effectively killed with chlorine, there is additional evidence now that it should not be our first choice:  trihalomethanes.  These are harmful chemical compounds created when chlorine reacts with organic material often found in water sources.

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18 Comments on “Using Chlorine Bleach to Disinfect Water”

  1. Laura Says:

    A commenter of the Facebook site for PreppingtoSurvive pointed out that there is some question about Giardia is indeed killed by bleach alone. This article suggests that if the concentration of chlorine is high enough and the water temperature is also warm enough, it is pretty effective. Still, it never hurts to boil water before drinking it. That won’t clear up the cloudiness, but should render all the microbes within harmless to you.


  2. Laura Says:

    Another thought I should have mentioned is that you want to protect against environmental hazards in collected water too. Consider what fills a body of water- herbicidal crop run-off or roadside overflow? Not ideal choices. If you have a choice between sources, look for one that evidently supports life. Is there algae, are there turtles and fish? If so, then most likely the water is not too contaminated.


  3. millenniumfly Says:

    I always thought iodine was more shelf-stable than chlorine bleach? Regardless, I wouldn’t want to rely on bleach as a long term disinfection method as I’m pretty sure it’s not great for your health when used for long periods of time. I might suggest an actual filter system such as the Big Berkey for long term situations. Otherwise, bleach may be the way to go for just a few days or weeks.


    • Laura Says:

      I’m not sure about the shelf-life of iodine vs. bleach. You may be right. Iodine does have a pretty strong taste, though.

      I probably didn’t state this well enough, but I’d always try to leave the water out overnight at least to help some of the chlorine to dissipate.

      We have a Big Berkey water filter, and I’d definitely recommend getting one. Most people will not have done that, though. If you had to advise a neighbor about what to do or provide a way for them to have safe water, I wanted to give some information about how you may do that.

      Sorry I missed your comment at the time. Thanks for taking the time to leave one.


  4. Marvin Peterson Says:

    You really should look into Hydrogen Peroxide as an alternative to Chlorine Bleach. Hydrogen Peroxide is much less toxic to humans when used to purify water and it can be used for First Aid disinfectant as well.


  5. C Says:

    Something to also consider is your reaction to the treated water some people have bad reactions to bleach when it is used in this manner. Another method to consider is solar disinfection. It uses less energy and can kill organisms like boiling. More information here.


  6. Albvs Says:

    I spent three months down in Peru recently and I spoke with an expert in Lima before continuing to the volunteer site. The expert suggested a combination of chlorine treatment followed by filtration to then remove the chlorine.

    An alternative is to apply ultraviolet radiation (to render the pathogens so that they can’t reproduce). This method doesn’t actually kill whatever is in the water so I’d personally add filtration as well.

    I can vouch for a 0.2-micron filter similar to the kind they sell in camping stores. I’ve used it in Peru (pretty foul water down there) and in the states in places known to have Giardia. You backflush it so you never have to change the filter. I’ve never had to boil the water, just filter and drink it.

    Before this, I used to use the sanitizing pellets but they take at least 30 minutes and unfortunately they stain your drinking containers a nasty tint of color that makes you lose your thirst.

    I don’t like the smell of chlorine in my drinking water. As a bottle disinfectant I prefer mouthwash. I once read a document that described the effectiveness of Listerine–after 45 seconds that stuff will kill even the HIV virus. I put in one teaspoon to about a cup of water and then rinse the first bottle, pouring this into the next empty bottle to sanitize, etc. Don’t forget to pour what remains over all the caps to disinfect them, too.


  7. Mark Says:


    I love this site!

    I have been interested in water for a while. I used to be a diver for a living; then after a few college degrees, a journalist.

    I have cultured tap water in various locations around the U.S. and examined it under a medical binocular microscope.

    What you see will alarm you.

    Reading the warning on any tube of fluoride toothpaste will scare you stupid. Check it out yourself. Throw a little chlorine in it add a little iodine and …

    I have made water stills from soup kettles, whistling tea pots, espresso pots andpaint cans.

    Any form of heat (fire, car exhaust, sunlight, etc.) that will evaporate water then condense it back into its fluid form will yield pure water. It will desalinate sea water.

    I have demonstrated this many times.

    Nothing makes a better zealot than a convert.

    Also …

    Calcium Carbide chips and water make acetylene. It burns in water. I have made coffee in a snowbank using carbide chips alone.




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