How to Create Bleach from Pool Shock to Treat Water after SHTF (Calcium Hypochlorite)

August 30, 2021

Pool shock bleach for water treatmentIn this post, we will be making 600 parts per million bleach, similar to the concentration of store-bought bleach, out of Calcium Hypochlorite.  Once you know this method, you may not ever buy store-bought bleach again.  In fact, for $20 spent today, you will be able to make the equivalent of 768 gallons of bleach.  Do you like saving money because that $20 today would equate to about $5,093 in store-bought bleach?  That $20 spent today will allow you to treat 33,000 gallons of water, which is enough for a family of three to survive for ten years.

I have to say up front that this content is strictly for educational purposes.  If you go this route, you also hold CityPrepping and its associates blameless.  This is the recipe to make bleach.  Chlorine treatment, while simple in concept, must be carefully performed because too much chlorine can be toxic, and too little chlorine is ineffective.  If you want to know the proper procedures for mixing a 600 part per million chlorine solution, proceed.  

FloodingAfter any disaster, even disasters with low initial death tolls, most people die from lack of drinkable water.  Once pretty reliable municipal water systems can quickly become contaminated or stop flowing altogether.  Many don’t have adequate supplies or can use up what they have stored up sooner than expected.  You have to know how to harvest water from the wild and render it drinkable.  To do this, many turn to bleach to kill the organisms in the water that can make you violently ill or even kill you.

When you buy a bottle of bleach, it has a shelf life that begins to degrade after six months and is not very good at all after a year. The bleach will be highly effective for around six months and fine for home use for about nine months. Clorox, the leading manufacturer, recommends replacing any bottle of bleach that is over a year old.  While bleach is fine for water purification and surface sanitation, the concentration and age of the bleach introduce some uncertainty into the correct amount to safely use.  A better and more affordable method is to use Calcium Hypochlorite, more commonly known as pool shock.  I will demonstrate how to use that here. It has a shelf-stable life of ten years.  That is an obvious long-term solution that will get you a decade or more beyond any disaster.  Let’s do this…


For your safety, do this in a ventilated area and wear eye protection.  Add 2/3 teaspoon to 1 gallon of water to make 600 parts per million chlorine solution, sufficient to treat water.  I found out I didn’t have a ⅓ teaspoon, so I had to weigh 1 teaspoon of Calcium Hypochlorite and then subtract a third of it.  If you’re guesstimating a teaspoon with this in a survival situation, you will probably be alright.  The worst that could happen from eyeballing a teaspoon is you end up with a 500ppm mix, which is equivalent to store-bought bleach, or you end up at a higher 700ppm mix, which will take you longer to aerate.

Gently swirl or stir the mixture until fully dissolved.   This is similar to a  store-bought bleach.  You can use this chlorine solution for basic sanitation on any surface. Sanitizing

To use the mixture to disinfect water, use one tablespoon and 1/4 teaspoon of your new bleach mixture in 1 gallon of water.  I just use one gently rounded tablespoon.  That would be 1/3 cup in 5 gallons of water.  Stir it and let it stand for 30 minutes.  Chlorine needs at least 45 minutes of contact time with water to disinfect it. Some say 30 minutes, but the truth is that Giardia Protozoan can survive up to 45 minutes in chlorinated water.  To remove the bleach smell, pour the water back and forth between containers and allow it to stand for a period with full exposure to sun and air.  Sunlight will help to break down the chlorine.  This will render any biological organic contaminants inert.  This will not remove pollutants or particulate matter from the water.  For this, you will need to filter the water.

I am using water right out of my small backyard pond.  If you saw the things growing and swimming in there, I guarantee you that you wouldn’t want to drink it.  Still, in a disaster, my little koi pond will provide me a number of edible plants, animals, and hundreds of gallons of water.  In a future post, I’ll run this freshly treated water through a PortaWell, a portable emergency water filter with excellent output.  Subscribe to this channel to be notified when that video comes out.

Mosquito PupaYou can see here that I had pulled up some critters in my unfiltered pond water.  There was a mosquito pupa in there.  I left him in there as a control to make sure the bleach was going to be effective.  Sure enough, he was dead and floating next to some maidenhair moss.  When it comes to water from the wild there are 4 main organic components that can kill you or make you sick: parasites, bacteria, amoebas, and viruses.  Simply touching your mouth without washing your hands can transfer these microscopic killers to you.  That’s why it is important to treat your water and filter it.  Check out this site for more videos on the water in the wild.  

To understand chlorine in water, know that standard tap water often has residual chlorine levels between 0.2 and 0.5 mg/l.  Here I suggest you put some basic test strips with your prepping water supplies.  Strips come in a range of different types.  My preferred strips I will link to in the comments below.  They test for 16 different things, from chlorine and fluoride to hardness and pH.  The two tests we are interested in here are the Free Chlorine and Total Chlorine.  Free chlorine involves the amount of chlorine that can sanitize contaminants, while combined chlorine refers to chlorine that has been combined directly with the contaminants. Total chlorine is the sum of free chlorine and combined chlorine.  So, with my strips, I can derive the combined chlorine number by subtracting the free chlorine from the total chlorine.  That’s a lot to say, we just want to make sure our water is safe to drink.

We want our finished water to measure around four parts per million or lower chlorine.  Above that and we start to irritate our bodies.  At six or higher, we do damage to our internal and external membranes.  Also, you want your pH between 6.5 and 8.5.  Fortunately, with chlorine, we can smell it and taste it.  If it is high or seems high, continue to aerate and circulate your water until it is safely in range and doesn’t taste like pool water.  I checked the chlorine levels three times.  First, when I made the solution, the solution gave me a reading that was off the charts on pH and Chlorine.  That would do great harm to you if ingested directly.  I then measured the untreated 5 gallon batch of water.  It was at .05 chlorine and 7.8 pH, which is probably because I added water to the pond with my garden hose the night before.  

I then treated the 5 gallons with 1/3 cup of the solution and stirred it for a few minutes, waited 45 minutes with it in the sun, stirred again, and took a reading.  At this point, I could drink it, but considering the wildness of the source, I also want to filter it.  After waiting overnight after re-affixing the lid, it had a total chlorine reading of 0, imperceptible to the strips, and a pH of 7.2.  You could drink it at that level, and it should be free of live organic contaminants, but it is always better to filter it as well.  In another post, I will use a PortaWell to filter this to an absolutely clean state.

An activated charcoal filter will remove some chlorine from water.  Distillation will remove all chlorine.  Boiling water for 15 minutes will release all the chlorine in the water.  But these extremes aren’t needed with chlorine.  At room temperature, chlorine gas weighs less than air and will naturally evaporate off without boiling.  Cover the opening with a cloth, however, to minimize exposure to foreign organisms.  Boiling is the go-to for most people because you can see the boil and know you’re good.  I’ll tell you a secret, though; boiling isn’t necessary to render water safe to drink. 

Contrary to what many people believe, it is not necessary to boil water to make it safe to drink. Boiling is the go-to because it’s a visual confirmation of the successful sterilization of the water.  However, heating water to 65° C (149° F) for 6 minutes or to a higher temperature for a shorter time like 80° C (176° F) degrees for 10 minutes will kill all germs, viruses, and parasites.  This process is called pasteurization, and pasteurization is much easier to achieve than a boil, but you have to be able to measure temperature to make sure you’re in range.  For this reason, make sure a thermometer is also in your prepping supplies.

When it comes to drinking water in the wild, the two-step process of treatment and filtration is always your best bet, though some filters are at a micron level so low that they effectively strain out everything.  Those filters, however, can be costly and have an effective use period.  There are many different types of filters on the market, and we will review a couple of them on this channel.


“Shocking” refers to the process of adding chlorine or non-chlorine pool chemicals to the water to raise the “free chlorine” level. The goal is to increase this level to a point where contaminants such as algae, chloramines, and bacteria are destroyed.  Pool shock tends to be around  50% Calcium Hypochlorite or Trichloro-s-triazinetrione, derived from copper citrate.

If you use pool shock for massive water purification, make sure it doesn’t have other algaecides or fungicides in it.  Since that isn’t always listed in the active ingredients, I just went and purchased pure Calcium Hypochlorite for laboratory use so that I could be assured of a 99% or greater assay level.  Calcium hypochlorite is the main active ingredient of commercial products called bleaching powder, chlorine powder, or chlorinated lime, used for water treatment and as a bleaching agent.  At that purity level, it should be treated as you would any laboratory chemical.  It can cause severe tissue damage to the eyes, skin, and lungs, so take all safety precautions when handling, storing and mixing.

Calcium HypochloriteThe reason I recommend Calcium Hypochlorite, and here is a link, is because 1lb of this is a container about 1 1/2 inches wide and a little over 6 inches tall.   as It contains roughly 96 teaspoons.  That would allow a person to make 384 gallons of 600 parts per million chlorine solution.  That would enable a person to treat 18,432 gallons of water, roughly the equivalent of a 16 by 32 foot swimming pool.  Put another way, that’s enough water to be treated to allow a family of four the three gallons minimum per day that they would need for an incredible four years.  Whether you are starting up a community after a disaster or you’re just looking at ensuring your own drinkable water supply after everything falls apart, Calcium Hypochlorite is the big solution.

The other aspect of clean drinking water, however, is pollution– specifically non-organic pollution.  The chlorine solution will treat water against bacteria, protozoa, and viruses, and it will dissipate from the water through exposure to air and light. Still, it will have no effect on any chemical toxins in your water like benzene, pesticides, fertilizers, heavy metals, and so on.  This is just one part of the solution to the more significant problem of rendering water safe to drink.  You are more likely to succumb to organic contaminants when water is harvested from the wild.  So, you want to make sure part of your solution also involves a filter or process that will remove chemical toxins if you are using a source of water that is likely contaminated in these ways.  Still, these chemical toxins will be slower to do you harm or long-term damage than one pathogenic bacteria, virus, amoeba, or protozoa.  That’s why your first line of defense against drinking dirty, wild water is this method.Poisoned Water

I have to be honest and tell you that for under 20 bucks for 2 pounds of stable Calcium Hypochlorite and the ability to treat almost 33,000 gallons of water, you should definitely get this in your prepping supplies.  You need to keep the Calcium Hypochlorite stored in a cool and dry location like the majority of your preps, but your Calcium Hypochlorite has a nearly indefinite shelf life.  At the absolute longest, your bottle of bleach is only suitable for 24 months, and calculating the proper amount can be problematic after a while.

Because of its lightweight, concentration, and ease of use, this will be a game-changer for many.  Next time you run out of bleach, switch to mixing your own.  Leave that expensive store-bought bottle on the shelf, and you will always be ready with this method.  If you just start making your own bleach you’ll save hundreds of dollars in the long run. Remember, the only way I know if you like this post is if you let me know in the comments below. 

Keep prepping.

4.8 18 votes
Article Rating
Notify of
Inline Feedbacks
View all comments
3 months ago

The link you included for near pure calcium hypochlorite does not have any in stock. I am having difficulty finding it to purchase. Any help would be much appreciated!

3 months ago
Reply to  Cathy

I am also having a hard time finding calcium hypochlorite and could use some help in finding some.

7 months ago

Thanks for all the great work City Prepping team! I’m a big fan of your youtube channel. Anyway, I just noticed a possible typo you may want to address in the section about pasteurization – the higher temperature should correspond to a lower time right?

Related Posts

Would love your thoughts, please comment.x