What You Need to Know about Water Tablets
6 min read
Water purification tablets are an ideal one-step back up form of water treatment. They are especially good for Get Home Bags and Bug Out Bags because they are light weight and inexpensive. Water purification tablets are also great to store in your vehicle or your bug out location to disinfect water on demand. Even though you are limited to the supply you have on hand they offer an easy way to make questionable water safe while a larger purification system is being set-up.
I use water purification tablets in my backpack during recreational trips into the backcountry as a back-up form of water treatment. If the water supply I am drawing from is extremely shady I combine both a filter and the tablets to ensure my safety.
Aren’t They Toxic??
All water tablets are toxic to some extent. They all contain pre-measured tiny doses of substances that kill water pathogens but not the people drinking the water. As long as you are not eating them straight or crunching on them like mints they are safe when used as directed. If you would prefer not to use chemicals to sanitize your water there are several effective water purification methods that are chemical free like boiling and SODIS (water purification with sunlight).
What is Best, Tablets or Droplets?
Water purification tablets are usually recommended for bug out bags and get home bags over the liquid drops because tablets are lighter weight and easier to use in a high stress situation. Tablets are also the running choice for the military and FEMA.
What’s the Deal with Cryptosporidium and Giardia?
Cryptosporidium is a genus of apicomplexan protozoans that can cause gastrointestinal illness with diarrhea in humans. According to the CDC it is one of the most frequent causes of waterborne disease among humans in the United States. In a disaster situation where government maintained services are effected, it is highly likely that this protozoa parasite will find its way into our water supply. That is why it’s a big deal in emergency preparedness. (Source)

Public Domain Photo – CDC
Giardia is also an infectious protozoa and it is a big deal in emergency preparedness because it can have such a dramatic effect on your health. The symptoms of Giardia, may begin to appear 2 days after infection, include violent diarrhea, excess gas, stomach or abdominal cramps, upset stomach, and nausea. Resulting dehydration and nutritional loss may need immediate treatment (if it is available). The typical infection within an individual can be slight, resolve without treatment in about 2–6 weeks, although sometimes longer and sometimes the infection is more severe requiring immediate medical attention. In a disaster situation if medical help is not available and no one has time to keep you hydrated, the situation could become life threatening. (Source)
What type of Tablet is Best?
There are three main types of water purification tablets on the market right now, and they are not all equal – each one has strengths and weaknesses. Choose the purification tablet that works the best with your situation and location. I will briefly break down each type of tablet.
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Chlorine Tablets
Brand names you may recognize for this type of tablet are Aquatabs and Rothco’s Military “Chlor-Floc“.
NaDCC, also known as sodium dichloroisocyanurate or sodium troclosene, is a form of chlorine used for disinfection. NaDCC tablets are different and improved over the older chlorine based (halazone) tablets. They are available with different chlorine content (e.g. 3.5 mg to 10 g) to treat from 1 to 3000 liters at a time. They are usually effervescent (meaning that escaping carbon dioxide gas causes the tablets to dissolve quickly, with a ‘fizz’), allowing the tablet to dissolve in less than 1 minute. When added to water, NaDCC releases hydrochloric acid which reacts through oxidization with microorganisms and kills them. Many tablets advertise no chlorine after taste. Unopened NaDCC tablets have a shelf life of 3-5 years, if opened they should be discarded after 3 months. (Source) (Source 2)
General NaDCC use: Fill a container up with one quart of untreated water, filter water to remove large particles. Add one tablet (depending on manufacturer). Minimum wait time is 30 minutes, one hour will be more effective especially with colder water or water with a higher pH. Always follow product usage instructions to the letter. NaDCC is not effective on Cryptosporidium or Toxoplasma (which can be especially harmful to pregnant women and young children) but it is more effective on Giardia than iodine. Always follow product usage instructions to the letter. (Source) (Source 2)
Iodine Tablets
Brand names you may recognize for this type of tablet are Potable Aqua, Coleman, and Coghlans.
Iodine Tablets use iodine to purify contaminated water. Most iodine purification tablets tend to leave a funny taste to the water and some discoloration, however vitamin C or ascorbic acid can be added after the treatment time to improve the taste and remove the color. This often comes in the form of two bottles with two separate tablets. Iodine water treatment has been proven to be somewhat effective against Giardia and not effective against Crytosporidium. (Source)
General iodine tablet use: If water is turbid lightly filter it prior to purification. Next use two tablets (or however many the manufacturer requires) in one quart of questionable water and let it sit at least 30 minutes prior to drinking preferably one hour especially if the water is cold or cloudy. An unopened bottle of iodine tablets should last four years, while an opened bottle kept in a dark place should be discarded after one year. Always follow product usage instructions to the letter. (Source)
Chlorine Dioxide Tablets
Brand names you may recognize for this type of tablet are Katadyn, Potable Aqua, and Aquamira.
Even though the word “chlorine” is in the name, chlorine dioxide is neither iodine nor chlorine. It uses a highly active form of oxygen to purify water so it leaves absolutely zero taste. As a nice bonus the action of chlorine dioxide causes alot of sediment to drop out of suspension (fall to the bottom) leaving the container of water more clear and further improving flavor. While the general printed expiration date of chlorine dioxide is four years out, if it is kept in temperature controlled environment it can last indefinitely. Chlorine dioxide tablets are a good choice for those allergic to iodine, with thyroid problems, or on lithium. (click here to learn more about chlorine dioxide)
General chlorine dioxide use: Fill a container up with one quart of untreated water, filter water to remove large particles. Add one tablet. Keep it away from sunlight, and wait. 30 minutes will kill viruses and bacteria found in pretty clear good looking water 60°F and warmer. Four hours of wait time is required to kill protozoa, also four hours of wait time is required for all viruses and bacteria if the water is very cold and/or turbid. Always follow product usage instructions to the letter.
Inventory Issues
Nearly a year ago today American Preppers Network reported to you an inventory issue with all chlorine dioxide water purification tablets (due to a number of factors but the main one effecting inventories was that several government agencies had placed large orders and all of the manufacturers had standing contracts that needed to be fulfilled before surplus product could be made available to the public) and that they would be unavailable for 4 months. Those four months turned out to be almost a year.
Until last month chlorine dioxide tablets were completely out of stock and there was only a limited supply of chlorine dioxide droplets available. Granted there were many other types of iodine and chlorine water purification tablets available but chlorine dioxide tablets were completely out of stock. Considering that the supply line of chlorine dioxide tablets is so easily overwhelmed – I would recommend stocking up on them now, as a opposed to waiting until it sounds like a good idea, only to find out that they are once again out of stock. Better to have them and not need them – than need them and not have them.
Please note: There are many articles on the internet about water purification tablets – any similarities are merely coincidence.
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Thanks for the article, especially the Chart as we engineers like our charts and graphs. I have been reading a few articles on the subject. Your article hit right on for me as I don’t want to be an expert I just want to have safe water.
Good to the point article, as always.
Cal
Great and valuable article Stephnie. Thank you!
What do you know about a liquid product called “ASO” which says its “35% Strength Activated Stabilized Oxygen”?
I note that it’s primary active ingrediant is Chloride with smaller amounts of Sodium, Chromium and Iodine. It claims that 2 fl. oz can treat 50 gallons for long term storage.
Stabilized Oxygen has always been a fancy word for hydrogen peroxide. Hydrogen peroxide will improve the flavor of water but is not effective at ALL for purifying it. The EPA and WHO both advice against using Hydrogen Peroxide to purify water because in the amount one would actually have to add to water for it to truly be effective would be poisonous to humans. Here is what wikipedia says about Stabilized Oxygen:
“Liquid Oxygen is the name of a product that is a solution of hydrogen peroxide[1] and other compounds including sodium chloride (common salt) that claims to help with “jet lag, fatigue, altitude sickness, headaches, hangovers, youthful skin, energy, and insomnia”. Ken Harvey, a member of the World Health Organisation team that formulated criteria for the promotion of medicinal drugs and a member of Auspharm Consumer Health Watch, states that the product is “no more than salty water”, and that most forms of water carry some dissolved oxygen. The Federal Trade Commission has prosecuted purveyors of such products for making “blatantly false and unsubstantiated health claims”.
The product claims to have an effect through increasing the amount of oxygen in the body but this is unnecessary as oxygen is absorbed by the lungs via breathing. Consumption of hydrogen peroxide is associated with various risks.”
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After taking a look – it seems to me that they are using Chlorine and Iodine to disinfect the water and adding in pinch of Hydrogen Peroxide to improve the flavor. Personally I avoid all the “Stabilized Oxygen” products.
Here is some additional reading on it from Chemist who did some good research on the stuff: http://www.chem1.com/CQ/oxyscams.html
Stephanie,
Thanks for you fast reply to my question above. I went to the chemists site you suggested and its chock full of good info including a lot of myth busting. Taking this thread a bit further; I accept that generally,the oxygenated water claims and hype are bogus. That being said, on the ASO- All Things Good website,the claim isn’t that ASO is for water purification but rather for water preservation. However, I find no “real science” to support that claim either. Aquatabs, Potable Aqua and Aquamira appear to be strictly for disinfection of water already contaminated to varying degrees. What I’m trying to “drill down” on here is if one is storing water in advance of need (in my case food grade 50 gallon plastic barrels) and I’m filling them with city water which is clorinated and, ran through a in-line RV filter through a potable water RV hose, what would be the best way to treat this water (if at all) for long term storage as described?
Hi Brian,
I see what you are after, I was a little confused at first. If tap water is filtered and tested (as is standard procedure in most public water supplies) you can be reasonable certain it is free of protozoa, viruses, and bacteria. When storing tap water some people will add additional chlorine to tap water just to make sure nothing starts growing in there that might’ve hitched a ride in on the container or their own hands. This most likely would be bacteria or allege which chlorine excels at killing. This doesn’t replace the need to clean the containers, it would be in addition to clean containers.
The common ratio for such a preventative measure would be 2 drops of UNSCENTED household bleach per every liter of water or 1/8 of a tsp to one gallon. You can multiply from there. Of course you could also use water purification tablets for this purpose if you wanted – i would also be effective in preserving nice clean water for you to drink incase of an emergency but household bleach is so much more cost effective, and you’ll hardly notice the taste at all.
As long as the container is sealed shut – the water should be perfectly safe to drink upon opening. If the water tastes stale you can pour the water back and forth between a couple of containers to ‘freshen’ it up. It just adds some air back in the water.
I also know some people use vinegar in the same way, however, vinegar doesn’t quite have the same disinfecting properties as bleach does – so use vinegar at your own risk.
Hi,
Thanks for the article. We have a pretty safe source of water but still plan for the worst (like everyone right now the W VA water problem has be double checking things). Though I don’t anticipate having to use the tabs, I would like to have some on hand; do you know if they have any sort of shelf life? If they do have a shelf life, is it a marketing/sales shelf life (the tabs are fine but they want you to buy more) or is it a real shelf life where the product deteriorates over time?
Thanks a ton,
Stay hydrated!
Hi Tim,
Thanks for the feedback and question.
I mentioned the shelf life of each tablet above. Honestly I am not exactly sure what the printed expiration date is for each brand and type of tablet as they differ slightly. BUT I do know that chemically what I have quoted below for you and above in the article is accurate. Chlorine (NaDCC tablets) and Iodine tablets will begin to degrade after 4 years (you maybe could push that out a bit). IF you can keep Chlorine Dioxide in a temperature controlled dark space, and leave it unopened, you will get a longer storage life out of it.
Chlorine Dioxide: “While the general printed expiration date of chlorine dioxide is four years out, if it is kept in temperature controlled environment it can last indefinitely.”
Iodine Tablets: “An unopened bottle of iodine tablets should last four years, while an opened bottle kept in a dark place should be discarded after one year.”
Chlorine Tablets: “Unopened NaDCC tablets have a shelf life of 3-5 years, if opened they should be discarded after 3 months.”
Like many things the expiration is normally indicating that manufacturers cannot or won’t guarantee effectiveness after that date – it doesn’t necessarily mean the product instantly goes ‘bad’ on that date, it very well might remain effective for quite sometime especially if stored properly in a temperature controlled area.
Excellent Info Stephanie, Thank you. Per your information of Facebook that the Chlorine Dioxide tabs are back in stock, I picked up two boxes. I gave them a test run and suprisingly easy to use and no “Swimming pool” Chlorine taste. Thanks and please keep the tips coming!
Cheers,
Todd