Bleach for Water Purification

I see FEMA, the American Red Cross and others all recommending liquid Clorox, Purex or chlorine as a method for water purification in an emergency.  Bleach can be a good method of water purification, except they don’t mention that  liquid bleach has a shelve-life.

Clorox states on their website that bleach should be replaced every year.  This is for laundry use.  For water purification purposes, bleach has started to lose its strength at six months.  It takes about 4-8 weeks from the time chlorine bleach is made to reach your home. This leaves you 3-5 months where the bleach is at the effectiveness level stated on its label.

Avoid using bleaches that contain perfumes, dyes and other additives.  Use only regular household liquid bleach that contains 5.25 to 6.0 percent sodium hypochlorite.  Chlorox has recently come out with a new product “Clorox Ultra”.  They have changed the concentration of Sodium Hypochlorite (chlorine) from 5.25% concentration to 6%, and they have added Sodium Hydroxide.  They are doing this to reduce the size of the containers.  Chlorox has stated that this is safe to use for water purification.

Clorox Ultra, Chlorox, Purex or chlorine bleach may be used to disinfect water in the following amounts.  Four drops per quart gives 10 ppm in clear water.  This amount should be increased to eight drops in turbid (cloudy) water.  Sixteen drops will provide 10 ppm per gallon of clear water.  You should be able to get a slight odor of chlorine after the water sits for the 15 minutes.  If not, add more Clorox.

Warning – Chlorine will not reliably kill Giardia and Cryptosporidium.  SODIS, boiling, chlorine dioxide tablets and good water filters are more reliable.  While chlorine will not kill Giardia and Cryptosporidium reliably, it is effective against most other bacteria’s.

Don’t pour purified water into contaminated containers.  Sanitize your water jugs first and don’t forget the threads and caps.

Clorox Bleach Sanitizing Solution.
To sanitize containers, mix 1-tablespoon chlorine bleach into one gallon of water.  Always wash and rinse items first, and then let each item soak in chlorine bleach sanitizing Solution for 2 minutes then drain and air dry.

Now as we approach the beginning of a new year it is a good time to check any bleach you have stored and rotate it if needed.

We will discuss powdered chlorine in a future post.


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9 Responses to Bleach for Water Purification

  1. In my opinion, bleach is a last resort for water purification. Thanks for the heads up!

    • Mark says:

      If you just survived Hurricane Sandy, or Katrina, or Rita, bleach may be your only option. Just because you think it is a last resort doesn’t mean it shouldn’t be used. I hope I’m not coming across as I am putting you down or anything. But the best laid plans can be destroyed in a heartbeat. Mother Nature doesn’t say Oh, I’ll wipe out this house but leave this one standing with no damage. Granted I’ve seen tornado’s that do just that, but there is no way you can guarantee that it’s your house left standing. So everyone should know multiple ways of purifying water. In my 72 hr kit I have over a dozen coffee filter plus a small bottle of bleach. My Katadyn is for the house, not to carry on me.

    • Alexa says:

      Definitely a last resort, but it’s good to know that it’s at least an option. Better than literally dying of thirst, no?

  2. Matt in Oklahoma says:

    I use this method to store water and 1/2 cup in my 65gl barrels. This post is good info and something that can be carried into a ravaged area like a floods, tornado, hurricanes etc. especially by your MAG to assist.
    Good info on the dates and time lapse from maker to household

  3. KE4SKY says:

    My own preference is to use Betadine® (10% povidone-iodine) in a small dropper bottle. I first pre-filter all suspect water to remove the larger cyclospora, which are not reliably killed by iodine, then add 4 drops of Betadine® per liter, screw on the lid, and put away it in my pack. Half an hour later, it is ready to drink. I like this system because I carry Betadine® in my first aid kit anyway. For bulk supplies 30 ml of Betadine® disinfects 150 liters of water, enough for a ten-person work crew doing hard physical work in mild weather, including washing.


    Backer HD: Field Water Disinfection. In: Auerbach PS (ed): Wilderness Medicine: Management of Wilderness and Environmental Emergencies, 3rd Edition. Mosby, St. Louis, 1995.

  4. Wyam says:

    Instead of bleach for purification of water, there is a much better alternative, a chemical called “Food Grade” Hydrogen Peroxide which can be bought from the chemist. You can get a lot of information from the internet on Hydrogen Peroxide that can be used as a purification agent and at 3% strength added to water will revitalize your body with much needed oxygen. You can safely say it has medicinal value and at 30% strength it can cover wounds from contamination. It should be a part of your First Aid Kit.

  5. Don H says:

    How about using powdered pool chlorine? Seems like it would be more stable than Clorox and easier to store. How much powdered choline would one use to treat a gallon of water?

  6. Ron Hurst says:

    It appears from a video on Youtube!
    Pool shock will go quite a long way this video talks about it plus shows one of my favorite last minute extra water items The WaterBOB..

    • Matt in Oklahoma says:

      Pool shock is something that needs to be gone into in detail. Don’t ASSuME you can just buy it, store it and you are ready cause you watched a youcanpostanythingtube video one time otherwise you might put yourself and someone you care about in a hospital at a time when there are none. Those that have experience need to chime in now on storage, additives, vaporization etc so that others don’t mess up with things like metal sealed cans, mixing indoors etc

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