I’ve been getting a lot of questions about this topic lately and I thought it would be a good idea to do a more lengthy post on the subject.
As everyone knows, many municipal water systems use chlorine to disinfect water. Often, the use of chlorine is combined with other purification systems such as filtration and ultra violet treatments. All you have to do is sniff your water tap water – it’s no secret. Why chlorine? Simple – it works.
It just so happens that Sodium Hypochlorite is the active ingredient in common household bleach. Sodium Hypochlorite is the source of chlorine in bleach. Most ‘off-the-shelf’ bleach products will contain in between 4 and 6% available chlorine. It is in this range that all of the below information and ratios are based. You will want to read the label and verify this first – otherwise you are just guessing.
It’s important that you only use regular bleach – nothing fancy with flowers, fresh mountains and little teddy bears on the label. No frills – standard – unscented bleach. The label should look like below:
When it comes to disinfecting water, it seems there is a different ratio and percentage for all kinds of different purifying agents and it can get really confusing. It can be hard to keep these ratios and solutions straight but it is very important that we do. All of the liters, quarts, drops, gallons, mL, cups and percentages are very easy to loose track of. I have a very simple memory phrase when it comes to disinfecting water with bleach. Once you read this phrase, you will never forget how to disinfect water with bleach again. The phrase is:
You must be 21 to drink.
How simple is that? It is a simple reminder that you need 2 drops of bleach per 1 liter or quart of water – hence 21. And, that just happens to be the legal drinking age in the US so it’s very easy to remember. Now, you will never forget it. If you don’t have a 1 liter or 1 quart container in which to measure an exact amount of water, it’s OK. Just remember that there are 4 quarts in a gallon and you can guesstimate the amount from there. Everyone knows about how much is in 1 gallon. Think about 1 gallon of milk and divide into fourths. You do need to wait a while before drinking, though. The wait time is 30 minutes. I remember this with: 2 + 1 = 3.
Have you ever tried to get a couple drops out of a gallon of liquid. It’s actually not the easiest thing in the world to do. Here is how I do it. You just need the cap to the bottle and a little piece of paper – toilet paper works great.
Then, place your ‘paper wick’ into a full cap with one end hanging over and it will begin to wick up the liquid and when turned at a slight angle will provide you with nice steady consistent drip that you can easily count.
A note about the water
It is important that your water be clear and void of debris for the above calculations to be effective. Ideally, you are already beginning with clear water. However, have you ever heard of an IDEAL survival situation? Me neither. Consequently, you may need to Pre-Filter your water BEFORE you disinfect it. You can prefilter your water using a huge variety of items – sock, t-shirt, bandanna, dried grass, feminine hygiene product and the list goes on an on. You may even want to prefilter a couple of times. Chlorine will not disinfect sediments. If your water is cloudy, double the chlorine dose and the wait time.
Don’t Forget the Threads
If you are using a bottle with a threaded/screw-on cap, don’t forget to unscrew the cap a bit and slosh some of the chlorine treated water into the threads. Otherwise, the water trapped in these threads could contaminate your water all over again.
Using bleach to disinfect water isn’t just a back-yard survival tactic. It is even recommended by the Environmental Protection Agency (EPA) as a viable form of disinfecting water in an emergency scenario. You can check out their writings on their web-site here if you wish: http://water.epa.gov/drink/emerprep/emergencydisinfection.cfm They also cover Iodine.
Conclusion
Chlorine bleach is a very common item in our society. It’s good to know how we can use it to disinfect water if we needed to one day. As I always say, it’s better to know it and never use it than to not know and need it. Hopefully, this has cleared up some questions that anyone has about disinfecting water with bleach. It certainly isn’t the only available chemical that we can use to disinfect water but it is a very common and viable option.
Thoughts anyone?
Remember, it’s not IF but WHEN,
Creek
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Great suggestion for remembering how many drops of bleach to use – I’ll try this on my Scouts next time we are out (they never seem to remember anytime we review this!). Here in northern Indiana we don’t seem to be able to find many open camping areas with running water so we always carry it in, but we do have bleach and tablets just in case.
Thanks for this, Creek. I had a rough idea of number of drops to a gallon, but couldn’t remember for sure. I’d been meaning to look it up to make sure, and kept forgetting until I got your post. That’s a great method to remember how many drops to a quart. Thanks again!
No problem – thanks for your visit and comment!
I know they don’t cost much, but is there a store / site that sells Nalgene bottles at a decent cost, maybe if bought in bulk. Need to put together BOBs for the family and we don’t have any decent bottles to begin storing water in. Thanks!
@larryl – I’d probably buy local unless you can find free shipping from somewhere. I know that REIs prices are very competitive if you have one in your area or http://www.rei.com. Thanks for your comments & Good luck!
YankeePrepper has a youtube video showing how he uses pool shock to purify water as this stuff lasts for years unlike bleach. I bought some from WalMart for $10.
Buck – Thanks for sharing this. Creek
Couples of things…so sodium hypochlorite is not super stable. It degrades over time and more rapidly when exposed to light. So keeping a bottle on hand for emergencies is a good idea, but bare in mind that it is undergoing degradation from ~6% downward. In the dark, the rate is temperature dependent and I think pretty uniform in a cool place. I know that in the laboratory, people gave it a shelf life of two months (we standardized it) but that was for sensitive test or in my case, to treat batches of raw water.
I would say adding a drop for every year old it is would be a good rule, but you can probably find the degradation rate with a google search.
One is disinfecting with chlorine, not purifying. Be mindful of your water source. If you pick an urban watershed that receives stormwater runoff you are probably getting a healthy dose of organic chemicals, nitrates, or dissolved metals, that, over time would not be good for you. In a survival situation however a gastro illness is far worse than a little lifetime cancer exposure. But a little bit more on that.
Not only will chlorine “not disinfect sediments” (or more importantly the microbes that may be harbored by the particles), chlorine will react with dissolved organic matter present to form disinfect byproducts, the bulk of which are bad for you. Now Creek didn’t specifiy if this water came from a pond or the tap, but assume the worst here. If your water is highly colored (like dilute tea) you should do the following: treat it with chlorine while it is cool, and let it stay cool. The reaction rate between chlorine and organic matter increases with time. So discard even marginally colored (read high in organic matter) after several hours…use it to wash your salad or something. Don’t put it in your or on you unless you like trihalomethanes, haas, or other dbps too. One other thing about color…unless it is colored from iron-a rusty tank or something. This complicates things, because I cant recall the ox state of rust but that is going to scavenge some of your chlorine and reduce the effective dose. I would keep some of those chlorine test strips/kits on hand. Test your water after (a good way to gauge chlorine degradation too I reckon).
In general chlorine will also not kill giardia or crypto–so a filtered source is pretty important if you suspect you are sharing the water with animals. Boiling is always preferred but it takes time and resources often so chlorine has a role for sure, but be mindful of its age, your water source, etc.
Ryan – You make some AWESOME points here – thank you for the very thorough comment to this post. This is very good information. You clearly know your stuff when it comes to chlorine. Thanks! Creek
Happy to add–nice to know I didn’t get that masters in drinking water treatment for nothing. Maybe someday I can use it beyond being a smartalec on cool/interesting blogs and reddit.
This is a follow-up comment to Buck’s post about using Pool Shock to disinfect water. Granular Chlorine definitely has a longer shelf-life than liquid chlorine/bleach. Below is a statement taken directly from the Environmental Protection Agency web-site about how to use/mix granular chlorine to disinfect water. I thought everyone might find this interesting. It would be hard to memorize so I printed it and keep it with my water storage supplies just in case I ever need to reference it:
——————————-
From: http://water.epa.gov/drink/emerprep/emergencydisinfection.cfm
Add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately ¼ ounce) for each two gallons of water, or 5 milliliters (approximately 7 grams) per 7.5 liters of water. The mixture will produce a stock chlorine solution of approximately 500 milligrams per liter, since the calcium hypochlorite has available chlorine equal to 70 percent of its weight. To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100 parts of water to be treated. This is roughly equal to adding 1 pint (16 ounces) of stock chlorine to each 12.5 gallons of water or (approximately ½ liter to 50 liters of water) to be disinfected. To remove any objectionable chlorine odor, aerate the disinfected water by pouring it back and forth from one clean container to another.
You said you use 2 drops of bleach per quart/liter in this post. I noticed on your “31 Random Survival Number Facts” post you say use 4 drops per quart/liter. FEMA and Red Cross both recommend 16 drops per gallon (which equals 4 drops per quart). I’m just a bit confused on how many drops of bleach I should actually use.
Andrew- Good question. Anywhere from 2-4 are acceptable doses. The EPA suggests 2 and FEMA & Red Cross suggest 4. Still yet, these amounts are ultimately dependent on your water. With perfectly clear water from a seemingly safe source, you’ll be just fine with 2. With slightly murky or stagnant water I’d error on the side of caution and add 4 – maybe even 6. Bottom line – there is no black and white dosage – only shades of gray. Hope this helps man – thanks! Creek
ok so if i fill my 55 gallon barrels with my water and store in the garage do i need to add bleach to this or not ??? i have read different ways and need to know so i can move on to other things as in food storage
thanks sharlotte
Sharlotte- Yes, in my opinion you should add some kind of chemical purifier to stored water. Others may have different opinions on this. Most 55 gallon drum water storage kits come with a 2 part solution for this purpose. However, you can just as easily use household chlorine (4-6%). For 55 gallons I would put in about 7 teaspoons. The EPA dosage is 8 drops per gallon. 8 drops equals about 1/8 teaspoon – thus the 55 gallons needs just about 7. Your water should then have a shelf life of at least 1 year. Hope this helps. Creek
Yearzerosurvival.com likes your article!
Very well written advice in an easy to remember format. Nice job!
Remember…one of liquid chlorine’s biggest enemies is UV light. If you are worried about over chlorination… pour the water into a open vessel and leave exposed to the sun for probably 1 hr to 2 hrs and it will be removed.
Great info! I bet this is also great for pets drinking water.. if need be.
I am sure that you know this Sandi Masterson. It is great to know.
I've heard on Dual Survival that its 4 drops per quart / 16 per gallon?
It is important to remember that liquid bleach does not have a very good shelf life and will begin to loose its strength. Powdered or granular may be a better option. Can we get an article on that?
You never know, this article or the information in it may just save your life one day. As Creek says, "it’s better to know it and never use it than to not know and need it."
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