Better than Bleach: Use Calcium Hypochlorite to Disinfect Water

This article was originally posted at Survival Topics

Many outdoors men, survivalists, and households preparing for emergency disasters rely upon common household bleach as a disinfecting agent to make water safe to drink.

Bleach will destroy most (but NOT all!) disease causing organisms (boiling water to make it safe to drink is always the best method).

What is not well known is Calcium Hypochlorite is far better for chemically disinfecting water.

Old Way: Using Bleach to Disinfect Water

I cringe to think how many people have expired bleach in their disaster emergency kits that will be used for treating polluted water.

Those of us who have emergency preparedness stocks of survival food and survival gear often keep a gallon or two of unscented household bleach on hand for making safe drinking water in large quantities. Bleach is often the chemical of choice because it is commonly available and frequently mentioned when discussing the how-to’s of drinking water.

Typical fresh household chlorine bleach has about 5.35% chlorine content (be sure to read the label).

To use household bleach for disinfecting water:

  • Add two drops of bleach per quart or liter of water.
  • Stir it well.
  • Let the mixture stand for a half hour before drinking.

If the water is cloudy with suspended particles:

  • First filter the water as best you can.
  • Double the amount of bleach you add to the water.

Why Using Bleach to Disinfect Contaminated Water is a Problem

A little known problem with long term storage of bleach in your disaster emergency supply cache is that it degrades over time. Consulting a Chlorox bleach representative produced this statement:

“We recommend storing our bleach at room temperatures. It can be stored for about 6 months at temperatures between 50 and 70 degrees Fahrenheit. After this time, bleach will be begin to degrade at a rate of 20% each year until totally degraded to salt and water. Storing at temperatures much higher than 70 degrees Fahrenheit could cause the bleach to lose its effectiveness and degrade more rapidly. However, if you require 6% sodium hypochlorite, you should change your supply every 3 months.”

I cringe to think how many people have expired bleach in their disaster emergency kits that will be used for treating polluted water. Even what are considered reliable sources of information such as the EPA and the Federal Emergency Management Agency FEMA will show you how to use bleach to disinfect water but will leave out this exceedingly important piece of information.

This is why I created Survival Topics – to give you the real information you need to survive.

So if bleach is unreliable for long term storage in emergency preparedness kits then what other commonly available chemical methods of disinfecting water are there? As it turns out a better solution is easily available.

Use Calcium Hypochlorite to Disinfect Water

A 1-pound pag of calcium hypochlorite in granular form will treat up to 10,000 gallons of drinking water

Calcium hypochlorite is one of the best chemical disinfectants for water, better than household bleach by far. It destroys a variety of disease causing organisms including bacteria, yeast, fungus, spores, and viruses.

Calcium Hypochlorite is widely available for use as swimming pool chlorine tablets or white powder that is much more stable than chlorine. This is often known as “pool shock”.

How to Disinfect Water Using Calcium Hypochlorite

Using granular calcium hypochlorite to disinfect water is a two step process.

  • To make a stock of chlorine solution (do not drink this!) dissolve 1 heaping teaspoon (about one-quarter of an ounce) of high-test (78%) granular calcium hypochlorite for each two gallons (eight liters) of water.
  • To disinfect water add one part of the chlorine solution to 100 parts water to be treated.
  • Let the mixture sit for at least one-half hour before drinking.

Be sure to obtain the dry granular calcium hypochlorite since once it is made into a liquid solution it will begin to degrade and eventually become useless as a disinfecting agent. This also means you should make your treated drinking water in small batches, for example enough for a few weeks at a time at most.

Another plus for using calcium hypochlorite to disinfect water for emergency use is that a little goes a very long way. A 1-pound pag of calcium hypochlorite in granular form typically costs only a few US dollars and can be obtained in any swimming pool supply section of your hardware store or online. This amount will treat up to 10,000 gallons of drinking water, which is enough for a family of four for some six or seven years at a gallon per day per person!

Calcium hypochlorite will store for a long period of time and remain effective as a chemical drinking water treatment. So get rid of the household bleach and buy a can of Calcium hypochlorite for your disaster emergency water disinfection needs. It lasts far longer and treats far more water than the traditional chlorine bleach water disinfection treatment.

This article was originally posted at Survival Topics

The Prepper's Blueprint

Tess Pennington is the author of The Prepper’s Blueprint, a comprehensive guide that uses real-life scenarios to help you prepare for any disaster. Because a crisis rarely stops with a triggering event the aftermath can spiral, having the capacity to cripple our normal ways of life. The well-rounded, multi-layered approach outlined in the Blueprint helps you make sense of a wide array of preparedness concepts through easily digestible action items and supply lists.

Tess is also the author of the highly rated Prepper’s Cookbook, which helps you to create a plan for stocking, organizing and maintaining a proper emergency food supply and includes over 300 recipes for nutritious, delicious, life-saving meals. 

Visit her web site at for an extensive compilation of free information on preparedness, homesteading, and healthy living.

This information has been made available by Ready Nutrition

Originally published June 19th, 2010
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37 Responses to Better than Bleach: Use Calcium Hypochlorite to Disinfect Water

  1. David says:

    Is there anything specific to look at when selecting calcium hypochlorite?  I know nothing about it, so I want to be sure I get it right the first time.

  2. Jon says:

    I bought “Pool Shock” online via Amazon. Six pounds for about $20 plus s/h. Make sure you get the calicum hypochlorite not the sodium hypochlorite. All I could find in my area, at local stores, was the sodium variety, therefore, I had to look online.

  3. BubbaJ says:

    What about the “Other” ingrediants in pool shock?  What are they and what potential harmful effects.  A manufacturors rep told me today they don’t recommend the product for prolonged, continued, everyday use.  It’s OK to accidently gulp pool water, but not for drinking purposes.  Thoughts? Insight?

    • J.J. in FL. says:

      I belive when shocking a pool with cal. hypoclorite no one is alowed in the water for 24 to 48 hours. Gulping pool water after that every day isn’t going to harm you.

      • J.J. in FL. says:

        J.J. back again. This is for BUBBAJ. Did a lot of searching for his conerns about ‘OTHER’ ingrediants in calcium
        hypochlorite, ‘pool shock’. As with any list of ingrediants (non food or food) the first ingrediant is your largest amount. So here goes.
         First is chlorine; your active ingrediant 47>76%. Next is your OTHER ingrediants; sodium chloride (plan salt) 10>20%; cal.chlorate 0>5%; cal.chloride 0>5% (used in beer brewing, flavering pickles, A firming agent for turning soybean curd into tofu——). cal.hydroxide 0>4%; (also called slaked or pickling lime). cal.carbonate 0>4% (think of Tums/antacids).
        One last thing.Check Ph after treating. needs to be 7.2>7.6
        Thanks J.J.

      • Einstein says:

        If you are gulping pool water I don’t think anything is going to harm you at this point, as you obviously suffer from massive brain damage.  Most likely it’s from the vaccines you and your family have been lining up to get.  Have you noticed the kids are doing stupid things and not learning anything in school? You might as well just suck the mercury out of broken thermometers.  When you add in the fluoride (rat poison) in drinking water, aluminum oxide/barium (chemtrails) in the air and Monsanto’s poisons in GMO food, you haven’t got a chance.  You should concern yourself with the deliberate poisoning being done by this criminal government.  Don’t worry about a little chlorine in the pool, at least you have a choice not to drink it?
        It has always been recommended not to drink the pool water or eat the yellow snow.  This is even more true for public pools in urban areas where third world types use the pool as a toilet.

      • Skip Tindle says:

        Chemtrails LOL really?

      • Emily Summer says:

        Yes, really. Do some research.

  4. chris1a says:

    You can buy pure Calcium Hypochlorite online. Bubba, here is no long term health problems associated with 7mg per litre. i.e. on average this works out to around 14mg per day. Normal treated drinking water contains a lot more disolved solids  (up to 1500mg per litre) in the form of calcium, sodiium, chlorites, iron, lead, sulpahtes etc. 
    incidentally, treated  water contains around 6mg/l of calcium and 30mg/L of chlorine. So if you have issues with calcium hypo, you should stop drinking treated water and start distilling you  water. Distilled water is the only pure water.  Does not taste very good though.
    The only issue with Calcium Hypo is that it may not kill all organisms and does not remove contaminants.    

  5. chris1a says:

    PS. Even i you use pool shock, which contains 70% Calcium hypo, and 5% Calcium hydorxide, you get nowhere near the LD50. 
    LD50 for hypo is 800mg/Kg body weight
    LD50 for hydroxide is 7000mg/Kg body weight.
    You will have to drink 2500 litres of pool shock treated water in per day week to appoach these values. 


  6. Christopher says:

    Thanks for a great article, Tess!  I did some research on other sites and came to the conclusion (about two years ago) that you had the best solution . . . BUT you might want to amend your article to discuss long-term storage issues.

    Like many people, I store my disaster preparedness supplies in five-gallon buckets.  They’re handy for grab-and-go situations and they store nicely in the corner of the garage.  However, I have learned the hard way that you should NOT store pool shock this way.  In short, pool shock releases small amounts of what I assume is chlorine gas.  It’s apparently very corrosive when it accumulates which it will if the pool shock is sealed in any sort of airtight container.  I noticed that my yellow five-gallon bucket had bleached almost white and foolishly opened it to find out why.  I stopped coughing and the air in the garage cleared . . . eventually.  The accumulated fumes had eaten through the packaging of the pool shock which in turn released even more fumes that were in the process of eating through the bucket (and five-gallon buckets are pretty tough).

    Yes, I admit that it wasn’t my brightest moment.  And I’m happy to let others learn the easy way from my stupidity.

    So, the moral of the story is: don’t store your pool shock in an airtight container and if it is, then take it outside and have a hose ready when you open it (with a mask on).  Spraying water will beat the fumes down very quickly and then you can thoroughly rinse out your container and dispose of your ruined pool shock.

    As for how I’m going to store my pool shock going forward, I’m thinking that leaving it in an open container will allow the fumes to dissipate naturally as they are produced and avoid a repeat of the problem.  Perhaps I’ll still use the same five-gallon bucket and just leave the lid off . . . although I’m definitely open to others’ suggestions.

    • Mark says:

      WARNING! DO NOT STORE CALCIUM HYPOCHLORITE IN AN OPEN CONTAINER UNLESS YOU’RE A COMPLETE IDIOT!!!  Venting these HIGHLY corrosive vapors is NOT recommended and you should ignore Christopher’s advice to store your  calcium hypochlorite in an OPEN CONTAINER for the following reasons:
      1) Calcium hypochlorite emits an extremely penetrable GAS VAPOR which is able to penetrate most materials in your house.  If you do as Christopher recommends you’ll probably put your OPEN CALCIUM HYPOCHLORITE CONTAINER in your attached garage or worse yet inside your house possibly near your food storage (pantry or basement), this will lead to illness through vapor ingestion & food contamination.  You need to understand that  calcium hypochlorite vapors are able to penetrate plastic, cardboard, most metals (after it rusts holes through it), drywall, wood, and more.  ANY & ALL UNOPENED food in non-metallic containers (like cereal, rice, pasta, bread, flour, etc) will absorb the calcium hypochlorite vapors and become foul tasting and possibly dangerous to eat.  The vaporous gases will also accumulate in areas around your house (even if stored in your attached garage) as they will pass through walls and settle in your kitchen & bedrooms.
      2) These vapors are EXTREMELY CORROSIVE and will start to rust and corrode all iron based metals in your garage and home within a few months.  If you do as Christopher recommends your OPEN calcium hypochlorite container will rust everything from your car to your curling iron in little time. 
      3) It destroys the shelf life.  Especially if you live in a humid area, the vapors are actually the calcium hypochlorite dissolving and if you keep it in a vented container you’ll eventually have a solid brick which even if you were able to chisel a few grams of the side would be useless as all the active elements have evaporated.  Besides, the entire reason for using calcium hypochlorite over bleach is the 10 to 15 year shelf life.  Storing it in an open container would probably decrease the shelf life by 14 years.
      4) The calcium hypochlorite MSDS sheets recommends storage in a strong polyethylene package.  It also reinforces my previous points by saying:  “The substance is toxic to lungs, mucous membranes. Repeated or prolonged
      exposure to the substance can produce target organs damage. Repeated exposure of the eyes to a low level of dust can
      produce eye irritation. Repeated skin exposure can produce local skin destruction, or dermatitis. Repeated inhalation of dust
      can produce varying degree of respiratory irritation or lung damage”
      THE PROPER METHOD TO STORE & USE CALCIUM HYPOCHLORITE:  Calcium hypochlorite should be sealed in an air tight, thick, poly container.  THEN stored within another cabinet / container to prevent children from opening the container.  When opening the container for use DO NOT SPRAY AROUND THE CONTAINER WITH A HOSE as Christopher suggested, any water in that touches the calcium hypochlorite will activate it cause even MORE vapors while destroying the shelf life.  Simply take the container outside away from the house, open the lid and walk away for a couple minutes, this will allow the vapors enough time to dissipate (and probably kill your lawn).  While using the chemical put on a 3M vapor mask, if you don’t have one then simply wet down a bandanna and wrap around your face (not as safe as the vapor mask).

  7. Jimmy says:

    Sorry, 90 drops to a pint and there are 14500 drops in a quart. So you would need 145 drops to a quart and that is 7250% increase of calcium hypochlorite solution over household chlorine bleach. That is, if my math is right. I hope someone can help with this.

  8. Karen says:

    Thanks, Christopher, for the info.

  9. Herbert says:

    How much of the granular Chlorine High Test Hychlorite (HTH) do I need to add to 5000 litres of water for drinking (Tank). Please I would appreciate if you could show how it is calculated.

    Thank you 

  10. dok9874 says:

    I have a 275 gallon water tote filled already, but untreated.  Since math and I do not get along, how much cal-hypo do I need to add to the 275 gallons to treat it?  Or should I just treat it as it is used?  I’d rather treat the whole thing, that way I don’t have to keep handling the bleach.  Thanks.

    • Doc,

      I would treat it at the time of being stored and then again when it is about to be used. The reason being is that calcium hypochlorite evaporates over time. This is why if you have a swimming pool you have to continuously add chlorine to the water to keep it clean. And treating the water per use would ensure you are consuming quality drinking water.

      Here is a chart based on FEMA’s recommendations:

      1 quart bottle 4 drops of bleach
      2 liter soda bottle 10 drops of bleach
      1 gallon jug 16 drops of bleach (1/8 tsp)
      2 gallon cooler 32 drops of bleach (1/4 tsp)
      5 gallon bottle 1 teaspoon of bleach


      To make sure that I give you all the information, the EPA (Environmental Protection Agency) has another set of numbers they go by:

      Add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately ¼ ounce) for each two gallons of water, or 5 milliliters (approximately 7 grams) per 7.5 liters of water. The mixture will produce a stock chlorine solution of approximately 500 milligrams per liter, since the calcium hypochlorite has available chlorine equal to 70 percent of its weight. To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100 parts of water to be treated. This is roughly equal to adding 1 pint (16 ounces) of stock chlorine to each 12.5 gallons of water or (approximately ½ liter to 50 liters of water) to be disinfected. To remove any objectionable chlorine odor, aerate the disinfected water by pouring it back and forth from one clean container to another.

      So much for consistency…. error on the side of caution and go with both.

      Also, follow these steps when storing long-term water storage containers:

      Ensure that your storage container is made of polyethylene plastic that is approved by the FDA for water storage. Purchase a barrel with as thick a wall as possible. The thicker the plastic walls, the better it will be at preventing foreign vapors from contaminating your water.
      Rinse the barrel thoroughly. Your barrel should be clean before adding your emergency water.
      Place the barrel in a location away from any direct sunlight. The location should be cool and dry.
      Always store your water away from any other containers that contain toxic substances such as kerosene, gasoline or pesticides.
      Fill the barrel with tap water. If you do not have access to tap water, use water from a well or other source. Add 3 tablespoons of bleach or calcium hypochlorite to your barrel after it is filled to ensure that bacteria or viruses will not be able thrive in the water as it sits in storage.
      Label the barrel with the date you filled the barrel with water and make it very clear that the content of the barrel is just water. Also include on the label how much bleach your have added to disinfect the water. Secure all caps and lids as required to close the barrel. Follow the manufacturer’s instructions for any specifics needed for your particular water storage barrel. Drain your barrel and repeat these steps every three years to ensure that you will have an emergency supply of clean water.

      I hope this helps.


    • Maybe says:

      1 teaspoon of 78% granular calcium hypochlorite makes 2 gal of solution mix with 100 parts water should equal 1 teaspoon = 202 gal of water or .25 oz makes = 202 gal; therefor .34oz = 275gal

  11. mark says:

    I’ve gone from totally ignorant to pretty well read up in the past year.  And only recently discovered Chlorine Dioxide.  Currently, I’d advise people to get enough ClO2 for 100 gallons, and while using that (which is very easy but expensive) get up to speed with using CalHypo. Add Koolaid for flavor and Cl neutralization, then use a .2 micron filter and no bigger to keep out the Cryptosporidium (1 micron) and you’ve got a complete system.  At least that’s what I’ve figured out over the past year. 
    I’ve been collecting all sorts of info about water sanitation during an emergency.  Anyone interested?

  12. Lauren says:

    If you just put only tap water into a clean barrel without adding bleach or other treatment, then would the water be OK to use if you filter it before drinking?  Or add the chlorine dioxide/iodine drops before drinking, just as if it were water from a lake or somewhere? 

  13. Katkinkate says:

    I would suggest another benefit of calcium hyperchloride to sodium:  it would be much better for grey water systems as the calcium would act as a soil conditioner while a build-up of sodium will destroy soil structure.

  14. Ashit Baran Dey says:

    Please inform me whats the actual dose of calcium hypochlorite for poultry drinking water

  15. terry whitlock says:

    i purchased mine from this guy through ebay

    with shipping and all it cost me approx $10.20 for 1 lb. thats enough to treat 10,000 gallons 

    • stcroix says:

      you can get a 3 pound can at wal-mart in the swimming pool section for $10.97
      just got one this morning.

      • Watchmanonwall says:

        you wrote this a year ago, so you may not come back and see this. But others will. Stay away from pool shock that has other “active” ingredients and other stuff like anti-fungal’s, or clarifiers and algae killers. They are harmful to your health and continued existence. Also the stuff from wally world will not be at 65% minimum. JJ above has a list of ingredients that are ok.

    • Allison says:

      He sells 73% but it’s supposed to be 68% or 70% — does that make any difference?

  16. Jim says:

    I bought my Pool Shock at Leslies Pool. It ALSO contains sodium chloride (not poisonous), calcium carbonate (used in antacids, so fine to consume), but then also:

    Calcium hydroxide 3%, which the National Institutes of Health warns calcium hydroxide is also toxic and can introduce serious health problems as a result of various types of exposure.:

    It also has calcium chlorite, which I don’t know if it is safe or not.
    Perhaps the concentrations are too low, when properly mixed, to be a concerned. But better to be informed than sorry!

  17. JR says:

    The EBay link is basically useless. It shows 73% calcium hypo. What’s the other 27%???? Arsenic? Plutionium? Most likely it has calcium dihydroxide and calcium chlorite, both poisons. Now, perhaps diluted enough it’s ok, but no word is made on any of this.  

  18. ron says:

    you folks have some very good information and advise.
    learning a lot from all of you, thanks for sharing your
    knowledge and learning more.

  19. Jedi Servant says:

    I used Calcium Hypochlorite to sanitize my bored water well last time instead of bleach and I had much better results. My bored well has a 24″ casing and is 80′ deep with about 15-20 feet of empty head at the top. I used 4 cups of CH dissolved in 4 gallons of water then poured the solution into the well. I then ran the water hose until I smelled chlorine and washed inside the casing and lid for several minutes. In addition you should run your household faucets until you smell chlorine then cut them off. Let the chlorine remain in the well for 24 hours then let pump the well dry. You are left with clean sparkling water – do this 2 times a year for best results.

  20. DreamingOfPan says:

    EPA instructions:

    Search site they recommend to find NSF certified products (putting in my state “Oregon” brought no results, but if I just choose the U.S. for the country, a whole bunch popped up):

  21. David Krutsinger says:

    Reverse Osmosis?

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