How to Purify Water with Household Bleach

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The water coming out of 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.

Take for example what happened in St. Louis this September.  A brief power outage disrupted water pressure, thus putting the entire water treatment system at risk.  As a result, residents were issued a boil alert – which means to boil water for at least 1 minute before drinking.

This wasn’t even a major disaster.  If a hurricane, earthquake, or flooding occurs, you can bet that the water isn’t going to be safe anymore.

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 major 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.

As a backup, you should also stockpile household bleach for purifying water during emergencies.

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

Sodium hypochlorite disinfects in the same way that chlorine does.  When mixed with water, a hypochlorous acid is formed.  This acid then turns into hydrochloric acid and oxygen.  It is the oxygen atom which 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 stomach lining and cause vomiting.  On the way back up, the sodium hypochlorite will damage the esophagus once again!

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

Normal household bleach only has sodium hypochlorite in concentrations of about 3-10%. 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 a 8.25% concentration of sodium hypochlorite, and it is further diluted in water.

So long as you follow the instructions, you will be fine 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!

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 end up with too much or too little bleach.  A medicine dropper is best.  You can also use teaspoon measurers.

Step 3: Pre-Filter Your Water if Necessary

If the water is cloudy, filter it first.  A camping filter is good 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, then 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 then 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 (such as 5% instead of 8.25%), then 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 for the purpose of treating 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 diarrhea and vomiting on top of it!

Remember that bleach will NOT remove chemical contaminants from water such as pesticides.  For these types of contaminants, you will need an additional water treatment method.

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

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  1. 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?

  2. 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.

    • 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.

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