water storage bleach

How Much Bleach To Purify Water – 55 Gallons – Ratio To Use

If you are storing water in containers, 55 gallon drums, or any bulk size tank or container, how much Regular Chlorine Bleach should you add to purify water?

This has been a common question. I’ve written about it a number of times over the years. I really haven’t changed my opinion about it, however it has been awhile since I brought up the topic. So here we go…

Do I Need To Add Bleach To My Water Storage?

It certainly won’t hurt and it will likely help if you add the right amount of bleach to your long term water storage containment.

If you are sourcing your water from your home’s municipal water supply, the water will already be treated to an extent (a small extent). Note that a typical municipal water supply likely measures between 0.5 and 1.0 ppm chlorine.

If your long term water storage is from your well, there will be nothing to inhibit organic contaminants (if there are any), so it may be a good idea to add some chlorine bleach.

Certainly if sourced from a pond or stream you should treat the water to eliminate organic contamination!

How Much Regular Bleach To Purify Water?

In a previous article, “Bleach – Water Ratio For Drinking Water” I listed the appropriate amount of bleach to add versus how many gallons of water being stored.

(Read on for the amounts…)

This would amount to enough chlorine to eliminate organic contamination from the water while keeping the overall chlorine level within safe limits.

The amounts listed will result in approximately 6 ppm initially, although will decay in time and interaction with organic contaminants.

Note: Important – Use “Regular” bleach (no additives, scents, etc..)

Regular Bleach containing 8.25% Sodium Hypochlorite

1 Quart water, 1 drop bleach
1 Gallon water, 6 drops bleach
5 Gallons water, 1/4 teaspoon bleach
10 Gallons water, 1/2 teaspoon bleach
50 Gallons water, 3 teaspoons bleach

Regular Bleach containing 5 – 6% Sodium Hypochlorite

1 Quart water, 2 drops bleach
1 Gallon water, 8 drops bleach
5 Gallons water, 1/2 teaspoon bleach
10 Gallons water, 3/4 teaspoon bleach
50 Gallons water, 4 teaspoons bleach

How Do I Know When I’ve Added Enough Bleach?

The rule of thumb is this…
If you can detect just a hint of chlorine smell in the water, it’s enough.

The amounts listed above will initially produce approximately 6 ppm, however that figure will drop depending on the chlorine interaction with organic contaminants. It will drop with time too.

You might use an ordinary basic swimming pool chlorine test kit to measure the amount of chlorine in the water.

>> Swimming Pool Chlorine Test Kit
(view on amzn)

Will I Need To Add More Bleach Later?

Bleach will break down after awhile. It actually reduces to salt.

I have read (I believe it was from Clorox) that the potency of regular chlorine bleach will diminish to approximately half strength after ~ 1 year.

That said, if your treated water is sealed in a container and stored properly, there should be no “new” contamination, even after a period of time.

What is “stored properly”?

– Closed up so nothing can get in
– Out of direct sunlight / excessive heat
– Preferably in a relatively cool place

Since chlorine does break down, it wouldn’t hurt to add more if you felt like doing that.

What I generally do is drain and replenish my water storage once a year. When it’s replenished I add chlorine bleach and it’s good to go for another year.

Why do I change my water storage every year?

Although it’s not necessary, because water is water is water, it simply puts my eyeballs on it for ‘just in case’ something went wrong. It makes me feel better…

[ Read: Is Stored Water Safe After One Year? ]

[ Read: Water Sources and Treatment ]


  1. Made casting of the bung in my big blue water barrels out of aluminum from beer cans. Next drilled a hole so I could put a hose fitting up and a clear hose that went to the bottom of the barrel down. The other bung has a exit only that hooks up to a hose. Turn on the water and ten minutes later the barrel is totally flushed. Use the exit water for garden and fruit trees flush the toilet or wash the dog. We have a Big Burkey water filter with the white filters below the black filters to take out chlorine. My choice is to suspend two one ounce silver bars in each barrel and have never had a problem with green water.

    1. This is the first I’ve heard of silver in your water…. what exactly does that do?

      1. Think of silver as a semi-heavy metal. As such, bacteria are killed in its presence. Copper does the same thing. Copper is used in bottom paint for boats to inhibit growth of marine life on the bottom. You might be able to achieve the same results by putting a piece of copper pipe in the drum.

      2. In the western expansion the wagon trains would put silver coins in the water barrel. Some say it was to hide it from theft but I think they knew it would keep the water safe to drink. The U.S. military is using cloth with silver impregnated into it. The concept is if threads are pull into a wound it will not get infected. We use colloidal silver on us and the live stock and it works.

        1. Awesome information folks! Thanks for clearing that up! I always learn something here… love it! :)

      3. Silver coins is what ships and pirates used to use to purify their water. Pretty cool

  2. There was some good discussion on CL in water a few days ago on MSB, you may go read up on the Chloramine, some water municipalities are now using, changes the entire scope on Chlorine. Comments were about ½ ways through the Comment Section.


    I will agree with Ken on the yearly “Changing-Out” of the stored water, all my “Old” water goes on the Garden after sitting in an open barrel for a few days to Vape-Off the Chlorine.
    This changing out of stored water take a very little bit of time, and well worth the effort to “Check” the storage system, would be a real bummer if you had a small pin-hole leak and drained the system sne did not know it when TSHTF.

  3. My main bulk water storage is an elevated 305gal black potable water grade plastic. Sunlight cannot penetrate. I started out draining and refilling every three months. Inspection of interior when drained, and inspection of drained water in a glass, showed no visual indicators of biological growth (algae, etc.). Increased to six month rotation with same results. It’s my opinion that water, at least water from a municipal source can be stored pretty long term (a year, maybe longer?) in opaque containers without further treatment, especially for my family since we drink only water that we’ve run through the Berkey anyway.

    Southernman; Great idea with the silver immersion. Pretty sure Berkey filters are silver impregnated with silver to destroy biologicals.

  4. Me Bad, I hardly store any water.

    But in my defense it rains a lot here and the water table is close to the surface and the largest fresh water system on the planet (The Great Lakes) is only a few miles away

    I have a creek a few hundred yards away that always has water in it.

    I also have numerous water filters.

    If I lived someplace with water shortage issues I would do different. But for where I am the larger problem is how to deal with an overabundance of water.

    We did have a water issue a few years ago (2014 I think?) with an algae bloom on the lake where Toledo get’s it’s water. The algae is a problem on the surface in hot temps. And the city of Toledo’s water inlet is on the surface so it gets into their water and for some reason it doesn’t get filtered out in the treatment plant.

    But I live next to Toledo in the city of Oregon. Oregon has their own water plant and the Oregon inlet is below the surface and doesn’t get the algae problems Toledo has.

    But I looked into my water filters and added a carbon pre-filter that filters out the algae. While it’s not needed, it’s nice to have it and I’m sure it filters out other nasty things.

    Never liked the smell of bleach water, I’m glad I don’t have to worry about using bleach.

    PS: I do have some bleach stored in the form of these big pill looking things. One pill dissolved in a cup of water gives you one-cup of normal bleach. I bought them at Menard’s (a home store) for under $3.00 a bottle of 30 or so.

    They are very shelf-stable and will last a long time. I suspect pool bleach powder is the same thing. But I have not researched it a lot as I don’t like using bleach and my water filters do the job I need done.

    1. none of your surface water sources will help you in the event of radioactive fallout

      1. Not a damn thing will help you in the event of radioactive fallout! At that point it is a slow painful death by radiation poisoning, or let the nuke fall right on my head. I would prefer that latter.

        1. Tia, Old people of Japan used Sea Kelp extensively…in the 40’s.

        2. Tia,
          True there is fallout in the US. But as OH said, there are things you can do to avoid its effect on you. First off is to quit smoking if you smoke. There is a direct correlation between smoking and lung cancer from radioactive particles. First noticed in uranium miners. Seems carbon/tars in the lungs of smokers bond with radioactive particles/radon, basically trapping them, and you become an emitter. Also, there is a component of cigarette smoke that is radioactive, from a radioactive daughter of Polonium that happens to be in the phosphate they fertilize the tobacco with. As for future exposure to possible future fallout events,…. yes, you can reduce exposure to within acceptable limits, it can be done. Look around on this site and others. Do not let fear of fallout overwhelm you, just be smart about it and learn how to alleviate its effects.

  5. I heard somewhere (maybe here) that bleaches shelf life could be prolonged by storing in an amber bottle. As luck would have it the next day a neighbor had a yard sale and had a couple of old amber glass gallon jugs for sale. I purchased one, poured a gallon of bleach into it and stored it in my pump shed. The shed is always in the shade and always cool. After a year I could hardly detect a bleach odor.

    I also read somewhere about a chlorine generator that ran off of 12 volts. Chlorine is the active ingredient in bleach and I know that 99% of the readers of this blog already know that. Chlorine comes from chloride the other half of sodium chloride more commonly known as table salt. The idea of being able to make my own chlorine was intriguing so I read up on it. to make a long story short I purchased a Mountain Safety Research chlorine generator. It runs off of 12 volts and uses table salt and water to produce a chlorine solution for water purification,

    Ready Made Resources sells them. Do a search for MSR SE 200. Price is $239.95. They are not available on Amazon.

    1. i bought the “Potable Aqua Pure Portable Electrolytic Water Purifier Device” on Amazon. It’s a portable bleach generator for $111. It fits in the palm of your hand. Quite small and portable. Great for treating drinking water, creating disinfectant solution, long term water storage, etc.

  6. Gentle Bloggers – I need some help. I want to store dry bleach for a JIC scenario, which I fervently hope never comes.

    However, I can’t tell from listings at vendors’ websites which products have ingredients to avoid, and which simply have inert ingredients that would cause no harm. Or is everything that is formulated for swimming pools considered safe to use to disinfect drinking/washing water?

    1. Anony Mee please use the search engine of your choice and type in Pool Shock for water purification. You will get several webpages. I prefer Backdoor Survival myself but I had to write the instructions down as I could not get a reasonable print out. You may have better luck.

      Chemical your looking for is Calcium Hypochlorite. You want PLAIN Pool Shock Nothing with anti-algae, PH Balance or whatever. Plain Pool Shock. The rest of the ingredients in plain pool shock is leftovers in making it. Inert from my container here before me.

      Using pool shock is a two step process and I ask you to follow the directions.

      Hope this helps.

    2. One caution when storing Calcium hypochlorite: Do NOT put it in a room with any metal that you like. Even the fumes are highly corrosive. Especially, do not keep it near ammunition. It will even corrode brass…. or so I’ve heard. I would never do such a silly thing.

  7. I think you should take a look at swimforhim.org . Thier minstry is distributing a very low cost chlorine generator in africa. They will sell them in the US for a contribution. One for you one for them seems about the rifght ratio to me.

  8. Great tool to pack in with your pool shock (calcium hypochlorite) is a combo pack of graduated measuring spoon and eye dropper for child medicine dosage – precision small measurement of dry and water mixed …… check the child care section of your local $1 store …

  9. This is a good article. It covers the important points. While this article covered bleach to water storage there is another thing to mention about bottled water. When you buy commercially bottled water (Dasani, Nestle, Wal-Mart, whatever brand) in 12 oz bottles, gallons, whatever, they never expire! If stored for a very long period of time it may have a plastic taste to the water from the bottle but it will still be safe to drink. Again, they don’t expire as long as the bottle remains intact.

    1. When we empty our commercial water bottles, I gather up a dozen or more, remove their lids, put them in a bowl & cover with bleach. I fill one bottle about 1/2 full of bleach, shake well, & pour into the next bottle. Then I fill each bottle from my tap & screw the lid on straight out of their bleach bath. There’s enough bleach clinging to the inside of the bottles & lids to approximate 2 drops. And it keeps our plastic bottles out of our oceans.

  10. Help from any of you guys greatly appreciated….I am a beginner in all this….a little late….but…want to be able to survive….at least for a little bit….I bought x3 55 gallon blue plastic containers I have resistance in my home to buy any more….going to also buy a bathtub liner to store water…..and then some containers of alkaline water……I have a filter system that came with the barrels………..I was going to put in bleach per the recipe in this one article after I clean out the barrels…can I clean them with regular soap first? suggestions for cleaning…. should I just put silver coins in the bottom….or both? Can you drink pool /spa water if you filter it first if it plain chlorine without algae…? Thank you guys….I don’t have any one mechanical or someone who can build things….limited resources too…..thank you.

    1. Wild Angel
      Just use a chlorine/water mix yo rinse, soap will leave a residue,

  11. Hi, a couple of questions:

    1. do you recommend using FDA-approved (food grade) hoses to fill water storage containers, 5 gallons and 55 gallons?

    2. what happens if the above-referenced size storage containers are not “stored properly” –they are out of sunlight, but in excessive heat? Currently in a storage shed and temperatures could get @ 100+ degrees Fahrenheit?

    Thanks for your expertise and time.

    1. Utahndrought.

      1. Probably isn’t too important if you’re going to add bleach. Us Southerners been drinking out of garden hoses for years. ; )
      If you are going to invest in a food grade hose anyways they sell RV filters that attach to water hoses that aren’t too bad to add to your on-hand gear as well. (Experienced camper.) Still need to sanitize but takes care of a lot of other stuff in the water. Even rust.

      2. Heat will not affect the stored water, especially if it’s out of sunlight. The bleach should kill anything living unless it is opened. If in doubt you can always resanitize before using.

      I’m happy you can store water. Got a feeling it’s going to be a long hot summer.

  12. Just Max, thank you!

    Just thought of another question:

    3. what about water storage in the winter in an outside shed? – in Utah the lowest it usually gets is low single digits (usually just a week or so), but generally teens to 32 degrees Fahrenheit.

    Appreciate your expertise and time.

    1. I’m hardly an expert. Like most here I’m pretty good at improvising on a fly if I need to though. Heating a shed just for water seems extreme so I’d say maybe when the time comes you can find a way to insulate your tank instead. Under my house is pretty much open and foam pipe wraps seem to work well enough to keep my pipes from freezing. I think foam sheeting or even old blankets could work. Important thing would be to make sure your tank didn’t expand and burst from freezing. For something more extreme or if something were to happen for longer term I’d consider something added. Maybe an electric blanket for a few hours? Water freezes at 32 and it’ll have to stay that cold for awhile to freeze a 55 gallon tank solid. Maybe not as long for a 5 gallon one though.

      I have a rain barrel that’s gone through the worst of the elements for years and it’s still fine. This year I setup an ICB tank collecting rain water for my garden. My intentions are to greenhouse this little area along with the tank by winter but I’ll likely have to consider trying this same idea for my own tank.

    2. Utahndrought,

      Assuming you have electricity, you might consider what I use on my 305 gallon outdoor water cistern. It’s a submersible stock tank heater from Tractor Supply. Thermostat controlled to only come on when water temps drop below 35 F. My tank is about five feet tall, the heating element has a protective shroud preventing direct contact of the heating element and the tank walls. I let it sit on the bottom. I gave around $30 for it several years back…I’m guessing it will cost more now.

      1. ….found it on Tractor Supply’s website. “Farm Innovators 1,500 watt Sinking Tank De-Icer”…$34.99

  13. Just Max and Dennis – thanks for the suggestions. Very kind of you – warms my heart for the coming winter!

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