How To Make Bleach From Pool Shock – Calcium Hypochlorite
Calcium Hypochlorite (also known as ‘Pool Shock’) is the main active ingredient of commercial products called bleaching powder or chlorine powder. It’s primary uses are for chlorinating / sanitizing swimming pools. This compound is relatively stable and has greater available chlorine than sodium hypochlorite (the active ingredient in Regular Bleach).
The advantage of Calcium Hypochlorite (pool shock) versus regular bleach is its shelf life when stored properly (dry, cool, dark). I’ve read at least 10+ years, as well as indefinite. In either case, it’s a great item for preparedness. Why? because just a single 1 pound bag of ~ 70% Calcium Hypochlorite can treat LOTS of water. Whereas regular bleach has a poor shelf life. Read more below regarding safe storage and how much water you can treat.
I always wanted to experiment and find out for myself — What is the formula to make your own equivalent Regular Bleach solution by using Calcium Hypochlorite (pool shock).
There are a number of results when you search the internet. But I wasn’t going to trust any of them without setting up my own temporary chemistry lab and testing for myself. I wanted to trust but verify. Well, I just did. Here’s what I found…
How Much Pool Shock (Calcium Hypochlorite) To Make Bleach
The following information is presented as a result of my own testing. It is in essence, not intended to be presented as absolute fact. Though I am confident in my own results. Feel free to duplicate the experiment with your own proof-of-concept.
Most of us are familiar with Regular Bleach. And preparedness-minded individuals may know how much Regular Bleach to disinfect water or sanitize surfaces (links below).
So my aim here with this post is to make equivalent Regular Bleach from Calcium Hypochlorite.
The quick answer is this. To make a bleach solution which approximates the strength of regular bleach concentrated at ~ 6% (sodium hypochlorite), use the following formula:
- 3 teaspoons (same as 1 tablespoon) of pool shock (~ 70% Calcium Hypochlorite)
- 1-1/2 cups of water
DO NOT DRINK THIS!
We’re talking about making your own bleach… which you wouldn’t drink, right?
To Make 1 Gallon of Bleach From Calcium Hypochlorite (Pool Shock)
- 11 Tablespoons of ~ 70% Calcium Hypochlorite
- 1 Gallon of water
You might be wondering why the seemingly odd amount of solution for my initial formula (1-1/2 cups). It was the basis for my testing:
It started with a document titled “TB MED 577” from the United States Department of the Army. Sanitary Control and Surveillance of Field Water Supplies. (view hard-copy on amzn)
In it, while referencing tables I-1 and I-2, (page 163 of this PDF), the 1-1/2 cups comes from a note regarding dissolving an amount of (“high-test” ~ 70%) Calcium Hypochlorite in a half canteen cup (1½ cups) of water. Their reference was canteen cups. So that’s where I started…
I began with the data from those two tables and then interpolated the amount of Calcium Hypochlorite necessary for the equivalent amount of Regular Bleach one would use to disinfect water.
[ Read: Bleach – Water Ratio for Drinking Water Purification ]
Long story short, the direct math from their tables worked out be about 2 teaspoons Calcium Hypochlorite per 1-1/2 cups water. However my real world chemistry lab tests revealed that 3 teaspoons of “high test” (~ 70%) Calcium Hypochlorite is closer to matching “regular bleach” with a 6% concentration of sodium hypochlorite.
This also matches with some of what I found while searching the internet in general.
Trust but Verify | How I Tested For Equivalency
First I acquired non-chlorinated water from a nearby source. The water was not muddy, dirty, or turbid. Though it had not been treated in any way.
Using fresh regular bleach (just purchased) with a 6% concentration of sodium hypochlorite… I used an eye-dropper to release 2 drops into a quart (1/4-gallon) of the aforementioned water.
Why? Because typically, 8 drops of said bleach per gallon of water will result in approximately 6 ppm (parts per million) (same as mg/L).
I verified with a chlorine test kit that the resulting ppm was in that range.
NOTE: Though 6 ppm is fairly high when it comes to chlorinated drinking water, if you’re using it to disinfect non-treated sources – the residual level (after the recommended 30 minutes) will drop. The more turbid the water, the more it will drop. Sometimes, a lot! That’s how it works.
After having established a baseline, I mixed up a batch with Calcium Hypochlorte. Firstly, 2 teaspoons with 1-1/2 cups water. I stirred it well, and let sit for several minutes. Then, using an eye-dropper, I deposited 2 drops into one quart of untreated water. I then measured chlorine level with a test kit. It was subjective, but it may have indicated ~ 2 ppm more or less. Certainly not as high as my results with Regular Bleach (though still would have been generally ‘good enough’).
Next batch. 3 teaspoons (same as 1 Tablespoon) of ~ 70% Calcium Hypochlorite with 1-1/2 cups water. Stirred it up. Then released 2 drops into another fresh batch of untreated water. Tested with chlorine test kit. The results were pretty similar to Regular Bleach. Being critical, the results were still appearing a little lower than Regular Bleach, but it’s subjective (lighting conditions and all).
So my final answer — How to make regular bleach equivalent by using calcium hypochlorite is any of the following:
1 Tablespoon per 1-1/2 cups water
2 teaspoons per cup of water
11 Tablespoons per gallon of water.
DO NOT DRINK THIS!
THIS IS EQUIVALENT TO REGULAR BLEACH.
Now That You’ve Made Your Own Bleach…
Bleach has a shelf life. My general advice is it may lose half it’s strength within a year. Your results may vary. So make what you need. You might save a few bleach jugs for use with making your own bleach from Calcium Hypochlorite.
Disinfect Water for Drinking
Make Your Own Disinfectant (NOT FOR DRINKING)
The amount of bleach you use is VERY DIFFERENT for drinking water versus disinfecting surfaces!
Refer to the following articles for more details:
[ Read: Bleach – Water Ratio for Drinking Water Purification ]
[ Read: Disinfectant Bleach – Water Ratio for Surfaces ]
How Many Gallons of Bleach From 1 Pound Bag of Pool Shock?
Using my digital scale, I measured 3 teaspoons of pool shock = 0.45 ounces (which makes 1-1/2 cups bleach equivalent).
So, a 1 pound bag is 16 ounces. That’s 16/0.45 = 35.5
35.5 x 1-1/2 cups = 53 cups = 3.3 gallons
How Much Water Will 1 Pound of Pool Shock Treat?
1 gallon of Regular Bleach can treat LOTS of water. It depends on the concentration used, the turbidity of the water, the organics within the water, etc. However if you use the formula of 8 drops per gallon – and if you do all the math – you end up with about 30,000 gallons of treated water from one pound of pool shock. Even if you halve that amount – factoring for more turbid water – you’re looking at treating ~ 15,000 gallons of water for drinking.
10K-plus (a good rule of thumb) per pound of pool shock (Calcium Hypochlorite).
Safe Storage of Pool Shock (Calcium Hypochlorite)
It’s corrosive. I recommend for long term storage, using glass. Canning jars? Vacuum Seal it? Other? Just saying… if you don’t store properly, it’s going to create a rust problem with all metals where it’s stored. So be careful.
68% Calcium Hypochlorite
(DryTec on amzn)
SAFETY with Chlorine
NEVER add water to the shock (Calcium Hypochlorite). ALWAYS add shock to the water. Chlorine gas can be debilitating in concentrations.
Use in well ventilated space.
Very useful article. I’ve kept pool shock for just in case I ran out of options with all other methods to disinfect water. Now I know the ratios. Previously I would have rednecked it up and probably gotten sick from it. Thanks Ken
NEVER add water to the shock. ALWAYS add shock to the water. Chlorine gas is debilitating and can kill.
Weslope- Good point. Calcium hypochlorite is far more dangerous to handle compared to sodium hypochlorite or “liquid bleach” mainly because the dosage is stronger and it can damage your lungs. Also be careful where you store it because if calcium hypochlorite comes in contact with grease or oil it can explode!
Gas. Chlorine gas.
You are right on about the rust problem. I kept mine in its original plastic bag, and sealed that inside an empty plastic peanut butter jar which I had cleaned with soap and water very thoroughly. Thinking it would be OK, I stored it in a wooden cabinet in my shop along with two air powered nail guns and 3 boxes of nails which the guns used. I didn’t get into that cabinet very often, probably a year or so before I needed my nail gun. ALL the nails were rusted, the guns themselves were all rusted badly where any metal was exposed to fumes leaking from the pool shock, through the seal on the lid of the peanut butter jar, which I assumed had sealed the pool shock from everything!
So I think you are right on regarding storing it inside a glass jar with a very good seal, and be sure to check it regularly.
My shop is unheated and not air conditioned and can get into the low hundreds temperature.
Perhaps that contributed to the pool shock outgassing. Just make sure you store yours’ correctly!
Use a plastic ammo box with a sealed lid.
What if you sealed the pool shock in Mylar bags? Would it still off gas like it would in a plastic container? Asking for a friend.
I would imagine it would to some degree. You might be notice a smaller amount of solid s and note chlorine fumes when the bag was opened.
Open outside.!
Probably don’t need to mention it but never mix ammonia with bleach! Very bad for your health if you breathe it in.
We tried storing pool shock years ago but did not like the gas it gave off. Instead we found/store “Evolve ” bleach tablets . Got’m at Wally World last year. 32 tablets per bottle.
It’s World War “V”, as Tallahassee say’s, ” It’s time to Nut-Up or Shut Up!”.
So stay safe and watch out fur dem hogs
How many tablets did you use to make a gallon of bleach?
Dick
Thank you for this information Ken. I was always unsure of how to mix this to make it bleach strength. That’s why I never bought any. I guess after the dust settles I will pick some up. That’s if the dust settles.
GREAT JOB Ken!!
When I was a young lad and needed money for summer I helped clean swimming pools, the guy I worked for had all of his chlorine in a 20 gallon blue plastic drum with a clamping ring on it, I hated popping that thing open, I would hold my breath and step away. The one thing I remember is that he never took this out of the back of his truck, rain or shine the truck was parked outside his house, the chlorine was always dry!! I actually have one now and keep my rice in it, but it stays in the pantry. :)
Thank You Ken for taking the time to experiment for us !:-)
Great article, Ken. You covered questions I hadn’t even thought of. Thank you for doing this!
There is a big difference between making a bleach solution and disinfecting water. The article states that this is a bleach equivalent and NOT disinfecting water for drinking.
Exactly. This is NOT about water purification for drinking. It’s about disinfecting surfaces. Big difference.
This recipe uses dry pool shock.
Can you use liquid shock? If so do you have a recipe for that?
Thank you Ken. Do you have formula/recipe for making 6% equivalent bleach solution from those pool floater tablets/hockey pucks?
I think you have tblsp & tsp mixed up
@x,
No, I checked again – all is correct as stated in the article.
3 Teaspoons (or 1 Tablespoon) per 1.5 cups water
or
2 Teaspoons per cup of water
or
11 Tablespoons (31 teaspoons) per gallon water
Note there are 3 teaspoons in a Tablespoon
Note there are 15.8 cups (16) in a Gallon
Hope that helps
i hope all is well in these crazy times, but i just had 1 question how much calcium hypochlorite would you need to disinfect a 5 gallon HDPE plastic water tank? for example like the 5 gallon Scepter water cans that the military uses? thank you for your time.
Good question.
This article provides the approximate formula to make equivalent regular bleach. From there, one could use existing guidelines for bleach disinfectants for various things (surfaces, water purification).
I have not calculated ratios for pool shock (calcium hypochlorite) directly to disinfecting solution applications. Though it’s on my “to do” list.
My purpose here was to make a gallon of bleach from pool shock.
To directly disinfect a 5 gallon container using pool shock with water would not require much pool shock. If and when I have time to test all that, I will post a new article. Thanks for the question.
Hi Ken, ive been looking around for HOCL ( Hypochlorous acid water ) and find out it is base from calcium hypochlorite.
-Concentrate solid form = Calcium Hypochlorite
-When solid form been diluated in water = Hypochlorous Acid water (HOCL)
is this correct ?
if yes, my question is why dont people use the solid form calcium hypochorite at cheaper price to make their own natural non toxic unharmful disinfectant instead of buying expensive and heavy HOCL or even home, industrial Generators using in many sectors ?
Thank you in advance for your knowledge on this subject !
I have a small 100 gallon pool and was told that I should use shock but I cannot figure out how much to add. Can you please help??
Kim,
How much pool shock to treat a swimming pool?
You might do a internet ‘search’ on that. And you will find that it depends on how dirty/algae your pool is, and other factors.
A one pound bag of pool shock (for example) is designed to treat a large quantity (read the label). For a small 100 gallon kiddie pool (for example) it’s going to involve doing some math (depending on the recommendations on your label and the chlorine level you wish to reach).
Can’t give you a specific beyond that without knowing more of your pool situation, the label directions on your bag of pool shock, and doing the research myself…
so how many grams of CalHypo 70% in 1000mL of Water to make 6% Stock Solution?
I think you made a fundamental error in your calculations. The document you cite says the solution created was by mixing 1 tsp of HTH per 1.5 cups of water. Not one Tbsp. Your following calculations would be wrong by extension. And in their charts it says the chlorine solution created is much weaker than 5% bleach, which is in their other chart for comparison.
Thanks for the information though. Thanks for posting the original document and referencing the page where ther charts are. It’s very useful. I extrapolated different amounts from them. I decided that making such a big batch of chlorine solution is wasteful for my prepping purposes. I reduced it to about 1/4 tsp HTH at 70% available chlorine for about 6 Tbsp of water to make the chlorine solution, since I probably would only use about 13 drops to sanitize 1 gallon of water.
I would love it if you verified the information I am giving you and got back to me.
Thanks!
Thank you very for sharing your information. One thing confuses me, however. In your calculations, you used a 70% concentration figure for the pool shock. But in your photo, it shows that the shock is actually 72% — how would that 2% difference change your ratios?? TY.
Thanks for the info. Most of the info on Google is useless (to me), as they use %’s and ppm, etc.
I have 3 1lb. plastic bottles of 70% hypochlorite and some 1 tsp measuring scoops from Amazon.
Now I know to use 33 level tspns to 1 gallon water for an empty 1 gallon bleach bottle.