How to Purify Water with Household Bleach

The water from your faucets is clean and safe to drink, right?

Well, it turns out that our water supply is a lot more fragile than we’d like to believe. It only takes a minor disaster to put water treatment plants out of order.

Boiling is one of the best water treatment methods because it kills bacteria, viruses, parasites, algae, and other common pathogens found in water (It won’t remove chemical contaminants, though; read this article to learn about water threats and how to treat them).

But there is a significant problem with boil alerts:

Boil alerts are commonly issued because power outages have put the water treatment system out of order.

And how are you supposed to boil water without power?

How Does Bleach Purify Water?

It is good advice to stockpile an emergency stove and fuel source with your emergency supplies so you can always boil water.

You should also stockpile household bleach for purifying water during emergencies as a backup.

Household bleach (chlorine bleach) contains sodium hypochlorite. The concentration of bleach is usually between 3 and 6 percent. However, some industrial-strength bleaches contain much higher percentages of sodium hypochlorite.

Sodium hypochlorite disinfects in the same way that chlorine does. When mixed with water, hypochlorous acid is formed. This acid then turns into hydrochloric acid and oxygen. It is the oxygen atom that does the purifying. It breaks down the chemical bonds of molecules and destroys them.

The great thing about using bleach for purifying water is that pathogens can’t develop a resistance to it. (Source)

Is It Safe to Purify Water with Bleach?

By itself, sodium hypochlorite is highly corrosive. If consumed in high concentrations, it can start to destroy human tissues. It will be particularly damaging to the esophagus. Once it reaches the stomach, it can damage the lining and cause vomiting. On the way back up, the sodium hypochlorite will damage the esophagus again!

But that is only what happens when consuming bleach with sodium hypochlorite in high concentrations.

Regular household bleach only has sodium hypochlorite in about 3-10% concentrations. If you were to take a swing of household bleach straight from the bottle (I’m not recommending you do this), you probably wouldn’t experience worse than an upset stomach. (Source)

The instructions below for purifying water with bleach are for an 8.25% concentration of sodium hypochlorite, which is further diluted in water.

So long as you follow the instructions, you will be OK drinking bleach for water purification. And it certainly beats the disease you could get from drinking contaminated water! Don’t forget that waterborne diseases are a leading killer!

But the Bleach MUST Be Free of Additives

Before you use bleach to purify water, make sure that the bleach only contains sodium hypochlorite and not any perfumes or other additives. Those can be toxic and make you sick!

Don’t Forget about Expiry Dates

Note that bleach gradually breaks down and loses its effectiveness; it generally has an expiration date of between 6 and 12 months.

You’ll want to ensure the bleach you use has the correct sodium hypochlorite concentration before using it for drinking water. Read more about bleach and expiration dates.

EPA Instructions for Purifying Water with Bleach

These instructions for purifying water with bleach are based on the EPA instructions. Note that the amounts are slightly different for different percentages of sodium hypochlorite.

Step 1: Find Household Bleach

It should say sodium hypochlorite 8.25% on the label. Do not use bleach, which has perfumes or other additives.

Step 2: Find a Measuring Device

You’ll want to measure carefully so you don’t get too much or too little bleach. A medicine dropper is best. You can also use teaspoon measures.

Step 3: Pre-Filter Your Water if Necessary

If the water is cloudy, filter it first. A camping filter is suitable for this, but you’ll still need to use bleach (or boil) because camping filters do not remove viruses. If you don’t have a camping filter, you can filter the dirty water through a coffee filter.

Step 4: Add Bleach

  • 1 quart/liter: 2 drops
  • 1 gallon: 6 drops
  • 2 gallons: 12 drops (1/8 teaspoon)
  • 4 gallons: ¼ teaspoon
  • 8 gallons: ½ teaspoon
  • Cloudy water: double the amount of bleach

Step 5: Let the Water Sit for 30 Minutes

Smell the water. It should smell slightly of chlorine. If it doesn’t, repeat the bleach dosage and let the water sit for another 15 minutes.


Remember that these instructions are based on 8.25% sodium hypochlorite and are what the EPA recommends.

how to purify water with bleach

What If You Don’t Have 8.25% Sodium Hypochlorite?

Household bleach comes in all sorts of different percentages of sodium hypochlorite. If your bleach has a lower percentage of sodium hypochlorite (5% instead of 8.25%), you’ll need to use more bleach.

The CDC, for example, bases its recommendations for treating water with bleach on a lower percentage (which they don’t specify). According to their instructions, you should have 8 drops of bleach per gallon of water.

It is best to prepare for disaster in advance – which means you have stockpiled bleach specifically to treat water and know exactly how many drops to use.

Don’t Forget the Caps!

This might seem excessive but don’t forget to purify the drops of water around the caps of your water bottles – especially if they have screw caps.

Bacteria, parasites, viruses, and other pathogens can be lurking in these tiny drops of water that didn’t get in contact with bleach. It doesn’t take much to end up with a stomach bug. When a major disaster has occurred, the last thing you need to add is diarrhea and vomiting on top of it!

Remember that bleach will NOT remove chemical contaminants such as pesticides from water. You will need an additional water treatment method for these types of pollutants.

Do you have bleach stockpiled for emergency water purification? What other disaster water treatment methods do you use?

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Leave a comment

  1. Thanks for the info. Where do you find bleach at 8.25% ? I can only find 7% in stores, but most bleach bottles don’t list a percentage at all.

  2. I preserve a lot of foods that we grow on our small farm and when I am canning (either water bath or pressure) and have extra space in the canner, I will fill jars with water and can it. The water is sterile and available to use at any time.

    Obviously not enough for long-term survival but it will get you by until you can create your filter and purification system.

    • Bleach expires because it is mixed with water. The water that you put bleach into will have to be treated again before you drink it. You need to stock up on hydroxycholoride . The same thing as you would treat your pool with and calculate to make your bleach when you need it. The hydoxychoride is very dangerous and needs to be stored carefully. You can find the delution rate online . The rate of bleach is about 4 drops to gallon of water. Hope this helps . Bleach expires 6 months after manufacture date. You will smell the difference in the strength of your bleach if you don’t use it for awhile. The bleach smell get weaker the longer you have yourbleach. Hope this helps.

    • Good question! There’s no reason to use both. If you have a choice, then iodine is actually better. Here’s from the University of Princeton website:
      “Iodine is light sensitive and must always be stored in a dark bottle. It works best if the water is over 68F (21C). Iodine has been shown to be more effect than chlorine-based treatments in inactivating Giardia cysts.”

      However, iodine does add a nasty taste to the water. Also, it’s not recommended for people with thyroid issues. Chlorine is easier to store and also has numerous other uses like disinfecting surfaces in your home. Iodine’s too messy to be used like that.

      I’m not sure if it would be safe to mix the two together. There are some science projects online where, when the two are mixed, it creates a reaction that causes the water to change color. No idea if this affects the efficacy of the chemicals in treating water though. That’s a question for a chemist.

  3. I bought a new refrigerator w/ an ice maker. The water filter on there ice maker was, of course, brand new. Not even a week later, the filter was putting out water that was 575 ppm! I went to Lowe’s, told them what was going on and they gave me another filter. I got the same thing. Within a week, it was trashed. I went back to Lowe’s and they told me I would have to buy a water filtering system for the lines supplying the ice maker and the water line in the kitchen. I bought a Pure water purifier, next. I got 5 gallons before it was putting out water measuring 535 to 575 ppm. Prior to buying the new fridge, I had purchased a Zero purifier that came with a tester. After less than 5 gallons the filter was trashed but the tester is still good! I am telling you this so you don’t put a bunch of misplaced faith in these water filtering systems out there. I live in a decent city but the water is “hard”. If you live in a city with hard water, your filters will clog as fast as mine did. That Zero tester opened my eyes to the use of other filtering system. ld help you out.

    Often considered acceptable range for carbon filtration, mountain springs or aquifers. 50-140 PPM
    Average tap water. 140-400 PPM
    Hard water. 170 PPM or above
    Less desirable 200-300 PPM

    Test all water you bring into your house, too. Not all water sold in stores is good for consumption. Wal-mart has a 1 gallon container that has a green lid. It usually always measure 0 to 10 ppm.

    Most water filters say they are good for months. That is not at all true. Get a teaster and measure for your sake and your family’s sake.

    • We quote the amounts recommended by the US Environmental Protection Agency (EPA). The confusion arises due to household bleaches having different percentages of the active ingredient – sodium hypochlorite. The EPA figures are based on 8.25% Sodium Hypochlorite but you may have to adjust accordingly.

  4. Thank you for sharing your experience in clean drinking water for survival. I have been learning as much as I can about survival tips such as edible plants in the forest and building with pallets, emergency shelters, rocket stoves, smokeless fire pit in the ground, ect. All must have skills need practice, gardening, have a supply of seeds learn garden tips. Knowledge is good but a person needs to practice that knowledge also. Thanks again.

  5. Getting powdered sodium hypochlorite to mix with water for bleach, how much to add to a gallon of water? Are there test strips you can get that won’t go bad?

    • Special Kitty litter ” jugs” hold approximately 3 gallons of water.
      I used one capful of bleach(generic $1 bottle) in each jug.
      Waited 24 hours, ran it through a water filter pitcher.
      Taste tested it. Useable. Made coffee.


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