How to Purify Water with Bleach

It is common to find bleach in abundance within the stashes and caches of preppers all over the globe. This is because bleach is something of a chemical multi-tool, just as handy as sanitizing surfaces and tools as it is for helping to keep human waste concerns under control. Bleach can do it all!

Perhaps most important of all its many attributes is its ability to purify and sterilize water that is contaminated with bacteria and viruses, making it safe to drink once more.

If this is news to you, don’t click away! It is absolutely true: using nothing more than regular household bleach you can purify water, purging it of microorganisms that can make you sick or worse you if you ingest them.

This is a well-known, completely proven and scientifically understood technique that anyone can do with just a little bit of know-how and virtually no prep.

But as you might be expecting, you have to know what you are doing. Bleach is a dangerous chemical if mishandled or ingested excessively.

Luckily, the technique for using it safely and getting repeatedly good results from it is a cinch with just a little bit of study and practice. In today’s article we will tell you everything you need to know.

Bleach Works! But You Have to Use the Right Kind

Most folks already know that bleach is a highly effective disinfectant that can sterilize all kinds of porous and nonporous surfaces of germs when used in the right concentration.

Why do you think bleach is such a regular fixture in cleaning supplies that you buy from the grocery store?

Quite a few people also mix their own bleach solutions for household cleaning performed weekly.

If you care to take a gander at the bleach aisle the next time you go to the store, you’ll be confronted with a wide variety of bleaches with optional additives: fragrances, thickeners, splashless additives and more.

Any kind of additive that I just listed will taint your water that you are trying to make safe to drink. Don’t chance it! When it comes to cleaning the house, making your white porcelain dishes sparkly brilliant again, or just doing the laundry like a normal person any kind of bleach will do.

But any kind of bleach will decidedly not do when it comes time to purify your water!

If you are trying to turn dodgy water into drinking water the only kind of bleach you can use is straight-up, no additive, no fragrance chlorine bleach.

Specifically you want to use bleach that is formulated with either a 6% or 8.25% chlorine solution, also labeled as sodium hypochlorite on the active ingredients list. So long as your bleach contains nothing but that active ingredient, you are ready for business.

Also keep in mind that some solutions containing bleach that are commonly sold, even ones with minimal ingredients, might be far weaker than the prescription above.

If they contain nothing but sodium hypochlorite they can in theory be used for the purposes of purifying water, but the ratios that I’m about to list will not work.

You’ll have to crunch the numbers and figure it out for yourself, or look elsewhere. If in doubt, just stick with the gallon jugs of common chlorine bleach that we are all used to.

Beware Old Bleach

Before you begin, you must make sure that your bleach is still fresh and active. Believe it or not bleach does have a shelf life!

Depending on the ambient conditions that it is stored in, you can reasonably expect to get around 6 or 7 months out of a jug of bleach before it begins to degrade significantly, losing anywhere from 15% to 25% of its efficacy each and every year.

Temperature plays a significant role in the lifespan of bleach, with colder temperatures or hotter ones speeding up this degradation. Keeping your bleach stored anywhere between 50 and 72 degrees Fahrenheit (10 to 22 C) will give it optimum shelf life.

In other words, don’t keep the bleach you intend to use for your survival supplies inside the room with your dryer, since it is likely to heat up significantly past that point while the dryer is running. Also take care to keep the bottle out of direct sunlight.

An unopened, unused bottle of bleach will eventually chemically decay into nothing more than salt and water, and saltwater is certainly not something you can drink and will definitely not do anything about the germs in your source of drinking water that you are trying to treat!

Make sure you mark and rotate the bottles of bleach in your survival supply just as you would when rotating water or food supplies.

Purifying Your Water with Bleach!

Purifying your water using bleach is the very picture of simplicity. All you need to do is add bleach to your water in the correct ratio, agitate slightly, then give it a short while to work.

After that, it is ready and safe to drink although there are a few additional steps that you might need to take depending on the taste of the water, or other factors like the temperature or turbidity of the water you are trying to purify.

The specific ratio of bleach to water that you will add varies depending on the quantity of water you are treating, but let us assume that you are treating a single gallon of water at a time.

In that case, you will add 6 drops of 8.25% chlorine bleach to that gallon, or 8 drops of 6% chlorine bleach.

It is important that you calculate these ratios fairly precisely, so having a good dropper for the occasion, or improvising one (see below) is an important part of making this process work. Adding too little or too much can have negative consequences.

After adding the bleach to your water, give it a good swirl or stir, and then all you need to do is wait about half an hour. If at the end of a half hour, your water does not smell of chlorine, you need to add a little bit more bleach, repeating the addition of 6 drops or 8 drops depending on its strength.

There are a few additional tweaks and adjustments you might need to make, but I will address those after the treatment procedures for varying amounts of water using the two most common strengths of household bleach just below:

Step-by-Step Instructions

  1. Clean Container – You will be working against your interests if you do not have your water in a relatively clean container before beginning. Make sure you remove all large debris, chunks of grime and slimy deposits from your container before drawing your water.
  2. Add Water – Self explanatory, but pre-filter it if it is necessary! Note that water that is cloudy or very cold will both take longer to treat, and require more bleach to treat successfully.
  3. Add Bleach – Add bleach using the ratios below and based on how much water you are treating and how strong your bleach is. Consult the table below for a guide. Be precise! Use a dropper.
  4. Agitate – Stir or swish the water to ensure the bleach solution is well-distributed. You should, at this point, be smelling chlorine coming from the water. If using any container with a top, spout or nozzle, make sure to open it enough for water to dribble out; this ensures contaminated water cannot hide within.
  5. Wait – Allow your water a half hour for the bleach to do its work, longer if it is cold or cloudy.
  6. Sniff – Give your water a cautious sniff after it has had time to sit; you should definitely smell chlorine, akin to a “pool” smell. If it is faint or has no odor at all, you should re-treat the water, starting over at Step #1.
  7. Improve Taste (Optional) – Your water is safe to drink as-is once it has been successfully treated, but some people get all choked up at the idea of drinking pool-flavored water. There are a couple things you can do to improve its flavor by reducing the odor of chlorine:
    a. Pour Off – By slowly pouring the water back and forth between two clean containers you can accelerate the decay of the chlorine and improve your water’s flavor.
    b. Wait Again – Giving your water more time to sit will see the chlorine smell steadily fade.
8.25% Sodium Hypochlorite Bleach6% Sodium Hypochlorite Bleach
Quart of Water : Add 2 dropsQuart of Water : Add 2 drops
Gallon of Water : Add 6 dropsGallon of Water : Add 8 drops
2 Gallons of Water : Add 12 drops2 Gallons of Water Add 16 drops
5 Gallons of Water :Add 30 drops5 Gallons of Water : Add 40 drops

Frequently Asked Questions

“Isn’t bleach harmful if swallowed? Says so right on the jug!”

The only correct answer to that question is “sometimes”. Bear with me. As with any chemical substance, in the correct quantities it might be harmful or even fatal if ingested.

Certainly bleach that is coming straight out of the bottle is extremely dangerous if you swallow it, and can likely even kill you. Sodium hypochlorite by itself, undiluted, is corrosive to biological matter, and can easily destroy tissues in your throat and organs.

Drinking a big swig of bleach all by itself is liable to cause real havoc and harm, but it won’t do that if it is diluted sufficiently in water.

The reason why is that when exposed to water, sodium hypochlorite undergoes a reaction where it releases oxygen atoms, and does so in great abundance. These rogue oxygen atoms are what actually destroys and kills the germs that are in your water.

By adding only a small amount of bleach to a comparatively large volume of water, the sodium hypochlorite that is so dangerous if ingested on its own is effectively neutralized as far as your tissues are concerned.

“I don’t have a dropper or any other way to measure my bleach precisely. What should I do?”

This is a surprisingly common complaint. The most obvious answer I would recommend is to procure a dropper, even if it is an old medicine dropper that you wash and keep for the purpose.

Alternatively, you can look up conversion tables that can tell you approximately how many drops are in common units of measure, be it teaspoons or tablespoons if you are treating larger quantities of water.

I am omitting them here because these are inherently less precise when using drops, because some people use tablespoons, and other people use measuring spoons that vary in their accuracy.

If in doubt, an extra drop one way or the other is not likely to cause any harm, especially when dealing with larger quantities of water.

One field expedient method you can use to fashion a dropper is to take a common table spoon and then lay a thin strip of paper or a strip of rigid cloth in the bowl of the spoon with one end hanging out and over the bowl.

Add your bleach carefully to the spoon, and capillary action will wick the bleach through the paper or cloth and allow it to slowly drip out of the free end. Presto, now you have a dropper.

“Does bleach get rid of all the contaminants in the water?”

NO. It bears repeating that bleach will do nothing to get rid of chemical or metal contaminants that might also be in your water. Bleach will only destroy biological contaminants, like viruses, bacteria and other organic threats.

Things like heavy metals and other chemical contamination will be completely unaffected by the bleach you add, no matter how strong it is.

For this reason, it is imperative that you appropriately filter any water that you suspect of being chemically contaminated before you perform your bleach treatment.


Using common, undoctored household bleach is a fast, easy and efficient way to purify drinking water sources of biological contaminants.

Requiring only minimal equipment and virtually no setup, this is one more tool in your toolbox that you can use to ensure you keep that most vital of provisions safe to drink in any emergency or prolonged disaster situation.

Make sure you keep plenty of bleach on hand, keep it rotated and know your ratios! Then you won’t have to worry about getting infected by your drinking water.

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2 thoughts on “How to Purify Water with Bleach”

  1. It seems to me the big question is the source of the water. If I fill my 600 gallons with city water do I still need to treat it? How long can I store the city water? What if it’s lake water?

  2. Given the short shelf life of liquid bleach, that not a lot of us use anymore, it would be good if you followed this up with a brief instruction on using powdered bleach like pool shock, or pool tabs, 3 inch pill shaped items. They both have longer shelf lives. Otherwise this is a great tip for the newer preparing populace, thanks.


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