How Much Bleach Do You Put in Water to Purify It?

Bleach is a prepper mainstay. Useful for keeping germs at bay on utensils, containers and surfaces, it is also handy for other sanitation concerns, especially those concerning bodily waste.

adding bleach in a water bottle
adding bleach in a water bottle

There’s seemingly nothing bleach cannot do, and it does it all for so precious little! But perhaps one of bleach’s best attributes is its ability to purify water.

You read that right: using nothing but plain, unscented bleach you can purify water that is of questionable quality, and make it safe to drink. At least, you can make it safe to drink if it has biological contaminants alone in it. Instructions courtesy of the EPA. Here’s how.

Using regular, unscented bleach containing 8.25% sodium hypochlorite add a small amount to clear but questionable water with a medicine dropper at a ratio of 6 drops to 1 gallon. This equates to a ¼ teaspoon for 4 gallons, and a ½ teaspoon for 8 gallons.

For lesser amounts of water, add bleach at a ratio of 2 drops to every liter. Note: these ratios only work for water clean of debris.

Murky water will impede the effectiveness of the bleach, and you should double the amount of bleach added to murky water if you have no choice. You should pre-filter any water that is not completely clear.

After adding bleach, let it sit for half an hour. When the time is up, the water should smell slightly of chlorine. If it does not, repeat the bleaching procedure at the prescribed strength.

You can do a little math yourself, and easily figure out that a single gallon of bleach can purify an awful lot of water and it can do it for just a couple of bucks. I punch those numbers into my calculator, and it makes a happy face!

Use the Right Bleach!

To ensure your bleach is effective at purifying your water source and it won’t hurt you, you need to use the right kind. Specifically you need to use real, straight-up, uncut chlorine bleach. AKA household bleach (which has a ton of alternative uses around the house).

Now, if you’ve been paying attention at your local grocery store and you’ve walked down the laundry aisle, you’ve probably seen three or four trolleys full of every kind of bleach imaginable. Scented bleaches, splashless bleaches, so-called oxygen bleach and on and on and on. You don’t want any of these in your readiness kit.

Any of those additives above will taint your water. Fragrances certainly will. I don’t know what makes bleach “splashless”, but it’s probably some kind of chemical thickener that increases its viscosity.

I promise you don’t want that in your water. Very best case scenario, your water will taste real bad. Worst case scenario, those additives can make you sick all by themselves, germs in the water notwithstanding.

Stick with plain, unscented, unthickened bleach. That’s it! Also check the label before you buy. The instructions above are for bleach comprised of an 8.25% concentration of sodium hypochlorite.

A digit or two in either direction won’t make much difference, but there are much stronger and much weaker bleaches out there that will require different instructions.

Some weaker bleach solutions for general-purpose household cleaning have significantly less punch than off-the-shelf gallon jugs of household bleach. Beware too of accidentally purchasing industrial-strength bleaches that have double, triple, or even higher concentrations of sodium hypochlorite.

As a rule, these are far too strong to use easily for purifying smaller quantities of water, and additionally, have serious hazards associated with handling them.

Isn’t Bleach Harmful if Ingested?

As with all such questions, the answer is “it depends.” let me be clear by stating up front, no fooling, you should never drink straight bleach no matter what Household bleach’s active ingredient is sodium hypochlorite.

By its lonesome, sodium hypochlorite is very corrosive and will easily destroy flesh, especially mucous membranes, in strong concentrations.

If you were to ingest a lot of bleach or very strong concentration of sodium hypochlorite, it would handily it dissolve the lining of your esophagus, and then do the same to your stomach once it got down there.

I’m not a doctor, but believe me when I tell you that that is no good and when the vomiting follows you’ll be getting a double whammy of stomach acids and the sodium hypochlorite coming back up. Trust me; it’s a bad way to die.

But it is the sodium hypochlorite, the active ingredient, that cleans the water. As you might expect from the name, it works much in the same way that chlorine does. When added to water, a chemical reaction occurs that results in the sodium hypochlorite releasing oxygen atoms in abundance.

These oxygen atoms are what actually does the killing of the gribblies hiding in the water. Fun fact: unlike medicines and other chemical cleansers, germs cannot develop any resistance or immunity to this chemical reaction since the oxygen atoms actually kill the germs by destroying their molecular bonds, pretty much disintegrating them. That’s pretty cool if you ask me.

At any rate, back on track: with typical household bleach concentrations of sodium hypochlorite that are further diluted in those small amounts in the water source you’re cleansing there’s no risk of harm to you so long as you follow the instructions.

Additional Helpful Tips

It must be restated that adding bleach to water will do nothing to get rid of chemical contaminants in it. You’ll have to rely on other filtration and purification methods to do that.

There is also an additional step you should implement if you’re adding bleach to water in any sort of screw-top, flip-top or nozzle-top container.

Contaminated water can lurk in and around the threads of the cap, in the nozzle and in similar places. It sounds paranoid, but all it takes is a handful of germs hiding in those drops that the bleach misses to make you dreadfully sick, potentially even kill you.

To smoke out these lurking germs, all you need to do is back the cap off the threads a couple of turns, open any stoppers, pop up any nozzles and so forth, enough to let water dribble out when you shake or upend the container.

After you’ve added the bleach per the instructions above, give the bottle of vigorous shake, and squeeze enough to send some water whooshing through these openings. Then just let it sit for the prescribed 30 minutes. By that time, any germs will have been killed in their hiding places and your water will be pathogen-free.


Adding six drops of regular, unscented 8.25% sodium hypochlorite bleach to a gallon of water is an effective method of sterilization. You can use this ratio adjusted for greater or lesser amounts of water effectively treat how much water you have on hand or require at the time.

2 thoughts on “How Much Bleach Do You Put in Water to Purify It?”

  1. I would like to state that Yes., bleach will kill the bacteria in water that is treated with it. BUT, it also kills the ‘good’ bacteria in your gut. That being said, there are ways to remove the excess chlorine from from water.
    If it’s only a glass full or jar full let is sit in the sun in and open container for 20-30 minutes.

    You can also use activated charcoal (you know, the stuff you find in filters for your fish tank). In fact that’s a great way to have a continual fresh filtered water supply. Just use a old fish tank (well cleaned) with fresh particulate and activated charcoal filter.
    Strait Vitamin C tablet or powder will also neutralize chlorine. 50 milligrams per gallon. The neutralization is almost instant. As soon as the tablet or powder is dissolved
    the chlorine is neutralized.

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