Water Purifying

Water Purification Tablets: How Do They Work + Best Products Reviews

Water purifiying kit

Traveling in the wilderness may eventually leave you without any safe water stores, and you will have to use what nature provides – water from streams, rivers, lakes, etc.

As pleasant as this sounds, it brings dangers in the form of germs, viruses, bacteria, and other impurities. Drinking straight from the river may not be such a good idea. You can use fire or heat sources to boil the water and kill bacteria, but that may not be true with some viruses.

Boiling has been used for centuries when it comes to disinfecting water, but today there are other methods of achieving the same effect. These include purifying and filtering systems, chemical solutions, water distilling systems, etc.

Purification tablets infographic

This article will focus on the water purification tablets used by many survivalists, campers, and hikers. Many of these pills provide safe water after 30 minutes.

Methods of Purifying Water Using Chemical Tablets

There are several popular methods for cleaning water using specific chemical tablets.


Iodine is often used in combination with other chemicals. This helps kill most of the existing pathogens and protozoa in the water, but it’s not perfect. It’s also true that it helps reduce the radioactive iodine in the human body; thus, it’s suitable for nuclear disaster situations.

After you let the iodine tablet work, you can pop in a vitamin C tablet to neutralize the taste of the water. However, it is important you not do this immediately.

Let the iodine work for about 30 minutes (in warm and relatively clean water) or more for cold and dirty water. After that, you can use an effervescent vitamin C tablet to make the taste more appealing.

Purifying tablets

Another iodine variation is the use of iodine crystals. You can use about 7 grams (0.25 ounces) of crystals in a small bottle (about 1 ounce) and then shake it well to help the crystals dissolve. If the water is relatively warm (about 25 degrees C/77 degrees F), the water will be safe to drink within 15 to 20 minutes. If the water is colder, allow it to stay a bit more – 30 minutes.

If the water is cold, you should be aware that some cysts may not be killed (like Giardia cysts), so it’s highly advisable to pre-warm the water before using the iodine crystals. Note that you should not consume these crystals in non-dissolved form, as they can be deadly.

Iodine crystals have an almost endless shelf life if they are not exposed to air. Ideally, they should be sealed and stored in glass bottles.

Storing them in a plastic bottle will let iodine fumes escape the plastic barrier and damage nearby steel materials, spoons, kitchen utilities, cookware, etc.

When a bottle is opened, it should be used within three months. If unopened, its life can be virtually endless.

Halazone Tablets

Another way to purify water is through the use of halazone tablets. They are based on chlorine. Since chlorine is more effective against E.coli bacteria, it is also widely used in low-hygienic areas and populations.

Iodine tablets can’t successfully fight E.coli. The only downside to chlorine-based pills is that they must be used within days (max three days) after being opened.

However, there is newer technology (sodium dichloroisocyanurate), and it has almost entirely replaced the use of halazone tablets.


Chlorine bleach tablets are widely used as an alternative to the above chemicals. However, they have to be used sparingly and are not suitable for long-term use. Use a 5% solution (unscented), two drops per liter will work. Wait for at least 30 minutes and at least one hour.

Another chemical sometimes used is silver ion, chloride-dioxide-based tablets. They can reportedly be effective against Giardia and Cryptosporidium. The downside to these tablets is that silver may accumulate in specific body tissues and cause argyria (changing the regular color of boy parts grey).

If you decide to use silver ion tablets, do it rarely and only if nothing else can be used. You should wait up to four hours to drink the solution.

Purifying Water Products in Tablet Form

There are a lot of water purifying options on the market. I’ll go through them so you can make an informed decision.

Polar Pure

Polar Pure

This product uses iodine crystals (crystalline iodine as the active ingredient). The product claims to kill viruses, bacteria, and protozoa. It also ensures that there will not be any unpleasant aftertaste when the iodine does its work, like with some other products.

Polar Pure’s products also last a long time. Some users claim that their crystals are effectively usable and work just fine even after ten or more years.

You have to keep in mind that these purifying tablets don’t clean or filter the sediments and particles in the water, so if you purify water that has too much dirt in it, it’s advisable to use it in addition to a filtering system. This will further cleanse the water and filter what’s left after using the crystal iodine tablets.

In addition, Polar Pure’s product offers a liquid solution, which lasts longer than the tablet form. The bottle has particle blockage, which stops the crystals inside from dropping into the water. Otherwise, the bottle has both a liquid solution and crystals for better purification.

The entire bottle can treat up to 2,000 quarts of water (about 1,892.70 liters), while the whole bottle is only 5 ounces (141.75 grams). So, to treat one liter of water (about a quart), you have to not use more than 0.07 grams. This is about two drops per liter. If you are unsure about the amount you should use, you can consult the bottle for the appropriate dosage.

Potable Aqua Tablets

Potable Aqua tablets

This is another well-known manufacturer, and it’s trusted among customers. This product offers two bottles – one purifies the water using iodine tablets (tetraglycine hydroperiodide), and the other PA+Plus bottle removes the aftertaste of iodine. The PA+Plus tablets are based on ascorbic acid (vitamin C), so they are harmless.

They neutralize the effect of iodine and render the chemical useless. All within about 3 minutes: this is why you should use the PA tablets only after 30-35 minutes of use, so you let the solution work. For every iodine tablet, one PA tablet is enough. Each bottle offers 50 pills, and all of them can purify 25 quarts/liters of water.

These tablets are also convenient and within 35 minutes your water will be ready to drink. You are advised not to use these tablets regularly, and these should be used only when you go camping/hiking.

Katadyn Micropur Tablets

Katadyn Micropur tablets

Katadyn is a trusted brand among hikers and campers. They produce tablets and other filtering and purifying systems and are among the top brands on the market.

One tablet from this product effectively treats 1 liter of water. It is effective against germs, viruses, harmful bacteria, etc. It also needs to work about 30 minutes after you put a tablet in the water. If the water is much dirtier than normal river water, you may have to leave the pills to work for up to 4 hours.

The product doesn’t leave any unpleasant aftertaste. It is also officially registered with the EPA as an effective antimicrobial purifier.

The active ingredient in this product is chlorine dioxide. It treats Giardia and Cryptosporidium cysts, but keep in mind that the tablets need to work for a different amount of time to treat either of these two.

For Giardia, let the tablets work for 30 minutes. Cryptosporidium cysts are much harder to kill, so the pills need to work up to 4 hours. Carefully plan your camping area/hiking route and research the water sources in these areas.

If they contain Cryptosporidium, plan to treat the water even if you don’t intend to drink it immediately.

Aquatab Water Purification Tablets

Aquatabs water purification tablets

These tablets are more effective when it comes to the amount of water one tablet can purify. One tablet is used for up to 2 liters of water, one of the advantages of the Aquatabs. Not only that, but they also destroy all the germs mentioned above, bacteria and viruses.

These tablets are also used by NATO, the World Health Organization, Red Cross, and many other international health organizations.

In addition to the above, they have a shelf life of about one year, as stated on the package. The water doesn’t have any bad taste or odor after being treated with Aquatabs. The water is ready to drink within 30 minutes.

These tablets also are capable of removing impurities, which the iodine tablets can’t. As a result, many people going on mountain expeditions to other continents use Aquatabs.

Aquatabs warn that these tablets may not be as effective if the water is too dirty and visibly murky. Since bacteria and protozoa ‘hide’ within the dirt particles and organic matter, you are highly advised to first filter the water.

If you don’t have a filtering system, you can use a t-shirt or other cloth to filter the impurities. As long as there isn’t too much organic matter in the water, the pills should work as intended.

Advice on Using Combined Water Purifying Wystems

Some experienced and professional survivalists recommend filtering water before treating it with any tablets since some organisms or bacteria live within impurities, organic particles, etc. This natural dirt protects them against the chemicals.

If you first filter the water, be sure to leave the water clear of particles, and it will be quicker to purify if using tablets. In addition, most tablets remove and neutralize metals and other minerals.

If you combine boiling the water with the above treatment, you will have even cleaner water. You don’t have to keep the water boiling for the recommended 10 minutes. Only one minute would be enough.

In addition, this will raise the water temperature, and the purifying tablets will work quicker. If you want to learn more about how to boil the water properly and read about other purification methods, check out our article on how to purify water.

Combined purifying

After boiling the water, filter it using a filtering or purifying system and drop in a purifying tablet. This combination will render the water ideal for drinking as there will be no dirt, viruses, and other contaminants.

Of course, if you don’t have a filtering system at hand, you can always make one using the items around you – to learn more about this, check out our tutorial on making a water filter.

This method will work as quickly as 30 minutes. Unfortunately, as we mentioned above, Cryptosporidium cysts take the longest to neutralize. Still, they can be killed within 30 minutes if the water is above 20 degrees C.

Finally, when you treat your water with these tablets, keep in mind that within 40 hours most of them will be compromised. This means that if you use a tablet now and let the water stand for more than 40 hours, the water may get contaminated again, as some bacteria will reproduce.

It is advised your drink treated water no more than 24 hours after it has been treated.

Also, chlorine, upon prolonged contact with UV light, dissipates, and the water’s purity will be compromised.

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About the author

David Dawson

David Dawson is a retired security specialist with over 20 years of experience. He worked for a secret manufacturing facilities and hospitals in Illinois. David's responsibility was to protect people in case of any disaster or cataclysm that might occur. Now he keeps on doing it through teaching others about how to prepare and survive flood, earthquake or even war.


  • The iodine tablets have proven useful time and again, a real life saver. I have several tablets tucked away in my Bug out Bag, and I always make sure to carry them when camping.

  • How dirty can the water be in order to be safe to drink with one of these tablets; I am assuming there is a limit on how contagious the water is, and these pills have limited powers.

  • I find the polar pure tablet efficient because of its small packaging and ease of usage. How sure are you that they can last up to 10 years? It is a good thing to pack in survival kits because there may be a time when clean water for drinking becomes scarce.

  • The Polar Pure quarts are EPA certified, east to use, and kills all bacteria & viruses. The shelf life is indefinite, but the bottle has to be airtight at all times.

  • What purifier do you often use? Personally, I want to go hiking and any of these might be useful during trips but since there are many options to choose from what would you recommend for first time users, such as myself?

  • I do recommend the Polar Pure iodine water filter purifier sterilizers because they are EPA certified, kills all bacteria & viruses, most cost effective, have indefinite shelf life, and are easy to use.

  • I always bring Aquatabs when hiking and camping, it is such an easy tablet to use and does not leave any bad taste or odor on the water. Another bonus is that it can purify a huge amount of water in only a short amount of time.

  • Definitely a good choice for water purification; aqua tablets remove iodine taste and color. The tablets are indeed easy to use, and they treat up to 25 quarts.

  • I find Oasis water purification tabs to be the best. More bang for your buck (17mg chlorine per tab which is fine for 2 litres at a time) and no bad taste in the water. I grab em off ebay.

  • Good choice, Dave. They are the best chlorine tablets for emergency purification of drinking water. Personally, I have used them twice and they did the magic for me.

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