What Is Bleach – And How Much To Use For Disinfection?


What is bleach?

According to Dr. Laundry on the Clorox website, “The active ingredient in household bleach is sodium hypochlorite, which is derived from salt.”

In fact, Clorox is headquartered in Oakland, California because they started making bleach there by running electricity through salt water from San Francisco Bay. So household bleach begins and ends as salt and water.

For example, during the laundering process, about 95 to 98 percent of household bleach quickly breaks down into oxidized salt.

Did you know that bleach can also be used to disinfect water of harmful organic contaminants, and do you know how much to use?


Regular Bleach To Disinfect Water For Drinking

To disinfect water for drinking, you can use ‘Regular’ household bleach.
This is a ~1 to ~2 ppm chlorine mixture using today’s concentrated 8.25% REGULAR bleach.

NOTE: The following numbers are ’rounded’ to the nearest ‘drop’
NOTE: You’re better off to have used extra ‘drops’ than not enough ;)

1 Quart water, 1 drop bleach
1 Gallon water, 5 drops bleach
5 Gallons water, 3/8 teaspoon bleach (or three 1/8th teaspoons)
10 Gallons water, 3/4 teaspoon bleach
50 Gallons water, 3.5 teaspoons bleach

Note: Stir the mixture and then let it stand for 30 minutes or longer before drinking water. Why? Because it can take that long to destroy Giardia Protozoan (common cause of diarrhea).

Note: Cloudy water w/ organic contaminants may take longer to disinfect, and may require more bleach to end up with enough residual ‘free chlorine’ to be effective. Rule-of-thumb if you barely detect a hint of chlorine smell afterwards, then you’re good to go…

Note: Typical municipal water supply measured at home is ~0.2 to ~0.5 ppm chlorine.

Note: According to the EPA, the maximum allowable concentration of of chlorine bleach in drinking water is apparently 4 ppm (parts per million).


Regular Bleach To Disinfect ‘Food Contact’ Surfaces

This is a ~200 ppm chlorine mixture using today’s concentrated 8.25% REGULAR bleach.

1 Gallon water, 2 teaspoons bleach


Regular Bleach To Disinfect ‘Non-Food’ Surfaces

This is a ~2500 ppm chlorine mixture using today’s concentrated 8.25% REGULAR bleach)

1 Gallon water, 1/2 Cup bleach

Note: Apparently, and generally after one year bleach may degrade to approximately half strength (although I’ve heard that it may be less than that) (Need to test this one day…).

Tip: Since bleach loses its potency over time, mark your newly purchased bottle with month/year, so you’ll know…

Tip: Always keep Bleach and Ammonia separate from each other.

Taylor Residential Water Test Kit


  1. Also keep in mind if and when the SHTF and you are worried about infections. As told by our family physician, put 1/4 cup – 1/2 cup of unconcentrated bleach in around 40 gallon bath mix well, soak for 10-20 minutes. This will kill and staph that may be on the body.
    We do this from time to time, just to be sure. A tiny scratch could turn into a big deal in no time here on the farm.

  2. MSR sells a small, battery powered device called Miox that allows you to produce your own chlorine for water purification from any salt product, table salt, Kosher salt, pickling and canning salt, rock salt, etc. Pricey but might be handier for bugging out than a gallon jug of chlorine bleach.

    1. MSR developed the Miox but I don’t see it on their website anymore. There is a used one on Amazon for $210. Sportsman’s Guide had some military surplus ones a while back.

      MSR currently has a MSR SE200 is available for $239 through their parent company, Cascades Designs. It produces a lot of solution and is designed to run off of a 12 volt battery or plug it into an automotive system. There is an additional 110 volt adapter for $60.

      A newer one is the H2gO Purifier by Aqua Research. It has a rechargeable battery that can be charged by the built in solar panel. The battery will last for 500 charges and can also be recharged by USB port. It doesn’t look to be field replaceable but I could be wrong.

      I’m not sure of how any of them would fair after an EMP but I believe the SE200 might be the simplest and thus lees likely to fail.

      1. Well I’m glad I got mine when I did. Didn’t know it had gone out of production.

  3. I use bleach, chlorine and Clorox cleanup for EVERYTHING!
    Cant beat the stuff,

    1. Yep, me too. Bleach is like a bullet to germs etc. Bacteria can’t evolve against a bullet. These antibacterial soaps etc. are not helping our health or environment.

    2. I use it diluted in my dog pen using only 20% bleach to 80% water. It kills worm eggs, kills bacteria, and kills the urine smell. I distribute it all over the pen, let it soak, then rinse with water. It beats the expensive anti=bacterial stuff vets push you to use to make money off you.

  4. I used to use bleach in my 55 gallon barrels but found my bleach degrades to fast. I use pool shock now, diluted and mixed with water before adding.

    1. Be careful with pool shock if you are drinking that water. Almost all of it has algaecides that are not intended for drinking. I have some for SHTF, but definitely would not be using shock on a regular basis.

  5. Bleach is a great disinfectant but as you said loses potency after a year. You can make your own bleach. 1/2 a teaspoon of pool shock to a gallon of water makes a gallon of bleach. Yes, you can mix it with water at the same ratio as bleach to purify it.

    1. Correction on the pool shock. You use 1/2 Tablespoon to a gallon of water. Calcium hypochlorite has a 10 year shelf life if store properly.

      1. Sterling Gal: Does 1/2 Tablespoon of Pool Shock & 1 gallon of water make the
        ‘newer’ 8.25%, Or, the older ratio of 5-6%? Purchased plain pool shock for storage, however never knew the formula/ratio of shock to water. I’ll make a tag and put with the shock. Thanks :)

  6. Happy New Year all!
    Big Thank You to Ken for running this spot, truly an excellent place to visit!

  7. I’m not sure how long bleach lasts but I believe they used to sell it in brown tinted glass bottles to slow it’s degradation. I put a half gallon up in a brown glass jug on 2/16/16. Going on 10 months and it still has a bleach odor. I guess what I’ll try and do is get a hold of some pH test strips and check it against fresh bleach on 2/16/17.

    As an aside we went to a new brewery in town the other night. Great beers and we asked if they were selling them off premises. They replied they were selling “growlers” to go. Growlers are a brown glass bottle that holds four pints. I see no reason that an empty growler bottle couldn’t be used for storing bleach. Just make sure it is properly labeled! And if course it will have to be emptied first, oh well another chore, (grin!)

    1. Brown glass jugs are what bleach used to come in, back in the day. Yeah I am a Boomer.

      1. a year or two back researched Bleach life effectiveness,
        and seem to recall three to six months.

        apparently it degrades, effectiveness degrades

  8. Should have added that in my get home bag there is a 2 oz. dropper bottle of bleach for quick disinfection of ground water. One is none and two is one,this is in addition to the Sawyer mini filter.

  9. I had a dug well at my house in Vermont. Every so often ((I’ve forgotten the required frequency) I would dump a 1/2 gallon of bleach in the well to ensure it was clean. Also dumped more in after dipping out the occasional frog or snake, those images always popped in my head when taking a drink of water…don’t miss that. Of course no problem when the well ran dry, had to tanker in 10,000 gallons to “prime” the well. Drilled wells in the area averaged 400 to 600 feet and a few quarts a minutes, hilly area.

    Anyway, bleach was my friend and I never did get “the grunge” from the water.

  10. This article says 1 drop per quart..5 drops per gallon for drinking.
    I clicked on the link below the article. Bleach to water ratio for drinking and it has a chart that says;

    2 drops/quart
    8 drops/gallon

    1. Just checked the EPA website. They say 2 drops/quart, 6 drops/gallon.
      Are there still 4 quarts in a gallon? Common core math/measurements?

    2. @Livin’ in the Woods,

      The numbers in my article are ’rounded’ so as to compensate for the newer 8.25% concentration. The formulas from the EPA, the CDC, the WHO, etc.. have been engineered to the lesser concentrate (which is no longer readily available).

      Additionally, when you’re talking about ‘drops’ of bleach with regards to disinfecting water, it’s not going to be a problem if you squirt some extra into the solution…

      Here’s some related information which may help you:

      Bleach – Water Ratio For Drinking Water

      Make Drinking Water Safe with Bleach

      Here’s something from the CDC, for example…

      ‘CDC’ instructions for safe drinking water with bleach:

      From the CDC, Centers for Disease Control, “If you don’t have clean, safe, bottled water and if boiling is not possible, you often can make water safer to drink by using a disinfectant, such as unscented household chlorine bleach”

      Add 1/8 teaspoon (or 8 drops; about 0.625 milliliters) of unscented liquid household chlorine (5–6%) bleach for each gallon of clear water (or 2 drops of bleach for each liter or each quart of clear water).

      Add 1/4 teaspoon (or 16 drops; about 1.50 milliliters) of bleach for each gallon of cloudy water (or 4 drops of bleach for each liter or each quart of cloudy water).

      Stir the mixture well.
      Let it stand for 30 minutes or longer before you use it.
      Store the disinfected water in clean, disinfected containers with tight covers.

  11. As I recall the bleach degrades through the plastic it is stored in. The question is will it degrade less if stored in glass. Many medications are stored in brown glass to increase their storage times. Keeping cool and in the dark tends to prolong storage. I did read in another blog recently that somebody was storing poolshock and was noting corrosion on other items stored nearby. Kind of makes me think that poolshock can out gas and the gas would most likely be chlorine. Probably fairly dilute. I’m not a chemist and would enjoy comments from those more knowledgeable than me.

  12. @Livin’ in the Woods

    I believe that with common core you get to pick your answer- just show how you got there. Have to see how that works out, eh? Otherwise, I still use 4 qt per gallon.

  13. When I was a paramedic, we kept a spray bottle with 50/50 mix of bleach and water for decontamination of blood in the patient area of the ambulance. We were told that would kill ALL harmful pathogens.

  14. Iodine had a longer shelf life. I keep a 2 oz bottle in my get home bag to treat ground water if needed.

  15. I am curious – why is the amount of bleach used to clean non=food surfaces more than that used to clean food surfaces?

    1. @lovelypoet, The reasoning is to minimize possible (food) exposure to very high levels of chlorine bleach. Additionally, the higher concentrate used for non-food surfaces will kill (disinfect) some very nasty contaminants (a good thing!).

  16. How much should we put into our 55 gallon water drums? Should we add some every 6 months? Thanks for article, because I don’t think we added enough.

    1. @Pojo, The answer to your first question is here, “Bleach – Water Ratio For Drinking Water”

      The answer to your second question is…

      So long as you have stored the water in an environment out of direct sunlight (which could potentially heat the water promoting algae/organic growth), and so long as the water containment is not exposed to new contaminants (by keeping a lid or cover open, etc..), the water which has been previously disinfected should simply remain clean of contamination.

      My own practice is to replace my long-term water storage once each year (just in case something’s going on in there that I was not aware of).

  17. I know liquid bleach can be used for disinfecting drinking water what I’m curious about is the use of dry bleach, can the dry crystals be added directly to water to disinfect and how much or should it be reconstituted first then added to water by the prescribed amount for liquid bleach?

  18. With some being concerned about the chlorine consumption, and others w/a legitimate concern about algaecides in pool shock, why not use H2O2 or hydrogen peroxide as a disinfectant and also as an algaecide?

    1. Chlorine has been used and is currently being used for public drinking water infrastructure disinfection all around the developed world. So long as concentrations are kept within safe limits (MAX 4ppm – although public water systems are generally kept around 0.5ppm), it is apparently safe.

      1. I remember a patient we had in the ER who mistook a water glass for one he had filled with bleach for the washing machine. Chugged the bleach, realized what he had done and came to the ER. Poison control was called and we were told that in the usual household concentration it was not a concern as it was to dilute to be harmful. I don’t now if this has changed with the newer stronger concentration. Please read up on this. What my point is, it is going to be to overdose on household bleach using it for water disinfection. If you think it may have degraded you are probably going to be safe if you double or triple the recommended amount. Once again, read up on this. Bleach ingestion is a good search term to use for looking in the web.

  19. Need to proof read these more. It is going to difficult to overdose on household bleach using it for water disinfection.

  20. I’m a nurse and I love bleach. We had a family holiday party last night, complete with a zillion grandkids coughing, sneezing and sharing microbes. Yuck. This morning I washed all the dishes and surfaces with a bleach solution. It kills everything. Papa and Nana do not want to share the cooties.
    I buy a new jug of bleach, put it on the shelf in the back and pull the front jug off to use. As Ken says, first in, first out.
    I like the idea of storing it in dark glass bottles. I remember Lysol sold this way.

  21. As a Certified Pool Operator and one who makes a living selling bleach (in many forms) we sanitize pools at 1-5 ppm. But it shouldn’t be consummed above 1 ppm, so make drinking water solution high, but let it sit in sunlight till it’s at 1 ppm or less. Heat and sunlight are the enemy of bleach. In fact for outdoor pools we use cyanuric acid to stabilize chlorine in pools as it dissipates very quickly in outdoor pools.

    The higher the % of concentration, the less stable it is. 3.25 is far more stable than 5%. That’s why I would rather use ppm instead of drops. Suppose you get 8% then it sits for a month in your hot garage before you use it? Now you need to increase you dosage, but by how much? It’s degraded, but who knows for sure. I recommend a good pool test kit. These can be purchased at any good pool supply store. Titration is exact. The Taylor kit is excellent.

    Also, bleach is one of the only disinfectants that will kill C-Diff, a nasty little bacteria. 5,000 ppm for that one.

    Restaurants use bleach for dish machine sanitation at 50 ppm, which is a national standard.

    Personally I have a few bags of Calcium Hypochlorite. It’s in a powder form and easier to carry of needed, more concentrated so I’ll need less and more stable than liquid bleach (sodium Hypochlorite). I keep it in a sealed bucket in my basement, and when I open it I take it outside first as it’s really pungent when I open it.

  22. Oh, and I will add that liquid bleach has a life span of about 90 days.

    1. The active ingredient in bleach, sodium hypochlorite, naturally breaks down into salt and water. The rate of breakdown increases rapidly when bleach is stored in extreme hot or freezing temperatures, or when a bottle is more than one year old. Generally, bleach stored at room temperature (~70°F) has a shelf life of one year, but after that point it should be replaced.


  23. Thanks Ken. Will print out some of this info to remember it. Kind of important, isn’t it?

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