Purifying water with bleach


Survival and preparedness is not all about zombies and being all “tacticool”. Often it is as simple as having water that is safe to drink. A well known method for disinfecting water is with common household bleach. Bleach is inexpensive and readily available at any grocery store.

Why bleach? Most municipalities use chlorine as part of their system to sanitize water for human consumption. Sodium hypochlorite is the active ingredient in bleach and is the source for chlorine. It is important when selecting bleach for water purification to only use regular bleach. Do not use scented bleach as you will be consuming the chemicals used for that feature.

How much to use?

Treating water with household bleach containing 5.25-8.25 percent chlorine
Volume of Water to be Treated Bleach Solution to Add
1 quart/1 liter 5 drops
1/2 gallon/2 quarts/2 liters 10 drops
1 gallon 1/4 teaspoon
5 gallons 1 teaspoon
10 gallons 2 teaspoons

The recommended guidelines listed above come from numerous government sources. Many survival/preparedness websites have been suggesting a lower quantity of 2 drops per quart.  This is probably just fine depending on the contamination level. Regardless – allow the treated water to sit for 60 minutes prior to consuming.

If water is cloudy or contains particles/sediment filter through a coffee filter, t-shift, or similar material prior to treating. It is worth noting is that bleach has no effect on chemical contamination.

Lastly – if boiling water is a possibility I would choose that method for purifying water over bleach.




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  1. Have you checked out making bleach from pool shock ? It’s highly concentrated and has one huge advantage, if you get the right chemical. Dry or crystalline powder keeps forever. Liquid bleach loses potency pretty quickly, and it is a pain to store space wise. I am having soem issue find the right pool shock locally. Seems HTH on Amazon will work… we’ll see
    Any opinions ?

    • you need to hit on a more professional pool maintenance level than what’s available at your Wally World store …. it’s that 70% concentrate level without all the pool additives that you need ….

      there’s brick & mortar supply outlets – depending on your locale – and plenty of Amazon suppliers out there ….

      nobody has mentioned it – calcium hypochlorite needs to be stored correctly – it is dangerous as hell if mis-handled ….

      • Illni
        Say on .. about the storage/handling problems.

        and BTW the guys around here that dig wells .. dump 1 gallon of bleach in them to make sure bugs don’t get in the water table.
        They let it sit open for 24 hours and say the bleach evaporates over the day.

  2. I’ve also heard that pool shock is great due to it’s long shelf life. I would suggest that whichever you use (bleach or pool shock) that you store kool-aid or some sort of flavoring next to it. I’ve never been fond of drinking swimming pool water. Even though you let it stand for 60 minutes before drinking you will still taste the bleach. Also, I’ve heard that if you store water already treated with bleach then when it comes time to drink it if the water doesn’t smell like bleach when you first open it you should put the same amount of bleach back into the water, stir it around then wait your 60 minutes before drinking. Just a thought.

  3. I have for years carried a Visine bottle with bleach while backpacking–makes it very easy to do the drops. Just be absolutely sure to remove the label and mark it as bleach.

  4. I’ve researched this and do not find it a viable solution for preppers, bleach has a expiration date of around three months to be effective , so unless you buy in powdered form which is very regulated, I’d take this info at face value, and keep it as knowledge for a storm, or a short term remedy, not a long term servival option. As a survival technique it’s great as a long-term viability water solution… Better off to learn how to make chlorine with electric current

    • sodium dichloroisocyanurate also known as NaDCC is the active ingredient in the Clorox Bleach crystals. This is precisely the same chemical used in survivalist tablets to purify water from streams etc. AND YES unlike some of the terrible information out here, it does in fact destroy Amelia and other protozoa. Relative variations in susceptibility were revealed; E. histolytica and G. lamblia were most susceptible (100% reduction) followed by Microsporidia then Cryptospridium and Cyclospora. NaDCC did not affect the consistency, color, taste or flavor of raw green vegetables and fruits.

      Thank you for your intelligent question.

  5. Curious where the info in the chart is from Rourke, and if there’s any notes that accompany it?

    From documents I found at the CDC, FEMA, and EPA websites, 1/4 tsp per gallon is the maximum amount for cloudy, very cold, or water that doesn’t have any odor of bleach after a first (1/8 tsp) treatment. Splitting hairs maybe since 1/4 tsp in a gallon wouldn’t be harmful, but you wouldn’t want to confuse the amount/directions of bleach to use and add 1/2 a tsp because the water was cloudy or cold to start with.

    The amount in a drop can vary too, Macgyver’s visine bottle (great idea) will likely produce different sized drops than letting a drop roll off a spoon. Think IV drip sets, the amount of drops in a milliliter can vary from 10-60 depending on what type of IV admin set is used, the number of drops in a ml or a tsp is not a constant.

      • That’s the truth, even the Washington State Department of Health that I believe you may have referenced for this post has two different sets of directions:


        My point was just not to confuse the maximum amount per gallon (1/4 tsp) with some directions that call for 1/8 tsp and doubling it for cold/cloudy water, or those that recommend 1/8 tsp and checking that the water has a faint odor of chlorine 30-60 minutes later.

        I read a preparedness book written by a supposed disaster expert that did just that, quoting: “To use bleach for disinfection, add a quarter teaspoon to a gallon of water. If the water is especially cloudy or exceptionally cold, double that amount”. He then recommended, “There should still be a faint whiff of chlorine smell. If not, do it all over again”. That would result in up to 1 tsp / gallon, or 4 times the maximum amount. Just saying.

  6. Okay here is the skinny on Sodium Hypochlorite being used for water purification. First of all these figures are for 68% Sodium Hypochlorite, so if your using something else you will need to alter your calculation. ** WARNING ** Chlorine Levels above 4ppm (4 parts per million) will harm your digestive system, and higher levels can lead to death.

    BE SURE TO CAREFULLY READ AND FOLLOW ALL HANDLING DIRECTIONS AND HEED ALL WARNINGS. It is always a good idea to be using calcium hypochlorite in an EXTREMELY well-ventilated area, (i.e. OUTSIDE!). If calcium hypochlorite becomes contaminated by foreign substances it can cause combustion. Do not breathe the dust or get it in your eyes. This stuff is not Play Dough.

    For granular calcium hypochlorite, 1oz = 50ml = 10.1 teaspoons
    A single one pound bag of 68% Calcium Hypochlorite will purify 10,000 gallons of water. Keep it sealed and dry. It does have an explosive quality but such activity is rare. Store Calcium Hypochlorite away from heat, and in a sealed container with general fire precautions (this is why they don’t make the 78% anymore). There are fewer problems with lower concentrations. Other inert ingredients are calcium. Many water purification facilities use this material. It is listed safe for consumption when properly diluted.
    First you want to make a Stock Bottle
    DO NOT DRINK THIS! Dissolve 1/2 heaping teaspoon, plus 1/8 teaspoon, granules into a one gallon jug.
    This is your stock bottle used to purify large amounts of water.
    Make this stock solution in small amounts as it will degrade over time. So make enough for a week or two at a time.
    To purify water add one part of this from your jug to 100 parts water.
    So one cup would purify 6.25 gallons. One gallon purifies 100 gallons of water
    Let the mixture sit for one hour before drinking

    1 gallon stock to 100 gallons water
    1/2 gallon stock to 50 gallons water
    1/4 gallon to 25 gallons water
    2 cups to 12.5 gallons water
    1 cup to 6.25 gallons water

    To treat clear raw water with 65-70% calcium hypochlorite there are a couple of ways to do it. If you want to directly treat the water with calcium hypochlorite use the following:
    1 Gallon: add one grain, about the size of the period at the end of this sentence.
    55 Gallons: add 1/8 teaspoon for a 5ppm solution.
    400 Gallons: add 1 level teaspoon for a 5ppm solution.

    To make a 5% chlorine solution to be able to use the drop method for disinfecting water, add and dissolve add ½ teaspoon of 65-70% calcium hypochlorite to ¾ cup of water. This will decay at the same rate of purchased 5.25% bleach so don’t make more than you will use in a fairly short time.

    Remember that prior to drinking this treated water, to agitate / aerate it (pour back and forth from one pitcher to another) to allow the chlorine (which wants to be a gas) to evaporate out of the water. Also if you can pre filter your water first it will help ensure that proper purification occurs.

    Here is a good water purification video on YouTube as well:

    I hope this helps and be sure to vet any (including my own) advice to ensure you are doing this correctly, and that you feel comfortable with the process.


    • Your post is inaccurate sodium dichloroisocyanurate also called NaDCC is quite effective at killing all the protozoa you mentioned and then some. I addressed this in a post above. I suggest you review it and cease henceforth from engaging in misinformation.I would have given you an F on my microbiology exam and prominently posted your grade in the Student Union for all to see.

  7. As a CPO (Certified Pool Operator) and a sales rep who has handled very large commercial laundries for almost 30 years, I just would add that any type of oxidizer will lose strength over time and that time will vary depending on the temp at which it is stored. A 1 gallon of bleach left out on a hot sunny day will be almost completely shot after a single day. If using a volume measure such as a teaspoon or drops, exactly how much of the “concentrate” will be needed to sanitize the water, if the said “concentrate” is a year old? Or five? THAT is the million dollar question. Regardless if using sodium hypochlorite (liquid bleach) or calcium hypo chlorite such as pool shock, I would suggest getting a Taylor test kit for measuring bleach solutions. If your “concentrate” is weak then using a volume measure could inadequately sanitize your drinking water which could be disastrous. However, by using a test kit, you simply add more till you get the desired level. By the way, you should not be drinking water with more than 1 PPM available chlorine. If you make it too strong, simply let it sit in the sun open and it will dissipate.

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