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Published Jul 4, 2022 8:35 AM

What’s faster? Light, lightning, or diarrhea? Answer: Diarrhea — because you run like lightning to the bathroom, turn on the light, and find the diarrhea beat you there. And while some people think it’s funny while it’s really brown and runny, getting a bad gut in the backcountry is no laughing matter. At best, it will make you miserable AF. At worst, you could die. So choosing water sources carefully is suuuuuuuuper important as is the method by which you purify your drinking water. 

To save your ass from your own bad decisions, your trusty writers here at Task & Purpose have reviewed many of the commonly available water purification tablets (and droplets) for your water treatment use. We reviewed specs, read some science stuff about bacteria, viruses, and protozoa, checked a few government websites, drank copious amounts of coffee and later beer, asked the Magic 8 Ball a few questions, and then prepared to elucidate so the next time you play pull my finger in the woods, your butt won’t let out a zinger.

Methodology

I gotta be honest with you: water purification tablets aren’t my first choice when moving through the hills. I prefer mechanical means to filter my water — like the GravityWorks Platypus or Katadyn BeFree or the Sawyer Squeeze systems. Sure, they’re heavier to carry than a bottle of drops or tablets, and sometimes unnecessary, but in the 30 plus years I’ve been going to the backcountry, I haven’t gotten sick yet. And I’m not saying tablets aren’t as good. In many cases they’re better, but they too have their downsides. More on that later. 

So, how did I choose products for this review? I went to people who love water purification tablets and asked for their opinions. I read countless reviews and also a bunch of scientific literature on their efficacy. Then I culled that list to the best ones based on a number of criteria. Essentially, I wanted to know several things: 1) Do they kill most of the creepy crawlies that will turn your guts into mud and ruin your day? 2) How long does it take them to work? 3) Do they make water taste ok or like ass afterwards? (You aren’t as likely to hydrate with water that repels you.) and 4) Are they simple to use?

When I go into the backcountry, I always carry a small Ziplock bag of essential emergency gear that contains a firestarter, compass, whistle, other stuff, and a bottle of water purification tablets. I rarely open this bag, but consider it to be my extra little bit of margin when assessing objective risks. I keep it as a backup in case my GravityWorks Platypus water purification system shits the bed. I used to carry Potable Aqua iodine tablets, but they taste like shit and I found out they don’t kill parasites like Cryptosporidium. Now, the Potable Aqua Chlorine Dioxide tablets are my top pick.

The secret ingredient in this biological warfare is chlorine dioxide, and it kills viruses, bacteria, Giardia, and Cryptosporidium. Chlorine dioxide is an improvement upon the regular chlorine that is used to treat most city tap water because the same amount of treatment can disinfect a larger quantity of water than normal chlorine. The thing I love about these tablets is that they’re effective, easy to use, and cover a wide spectrum of creepy crawlies that you’re most likely to encounter in wild water sources. They’re not without downsides, though.

While the water they treat tastes far better than iodine tablets, the chlorine taste is noticeable. Also, while the iodine tablets come in a hard, dark bottle, these tablets come in foil packets, which are lighter but also require more care to avoid puncturing. So, you’ll need to protect them in storage or in your backpack from exposure to light, water, and air. Also, they’re not fast for full protection.

While they’ll kill most bacteria and viruses in about 30 minutes, it takes a full four hours to kill Cryptosporidium for full protection. These tablets are lightweight, effective, and easy to use, but require planning ahead due to the wait time. Some users reported the chlorine caused them a scratchy throat. They’re also a dollar cheaper than the similar Katadyn MP1 chlorine dioxide tablets which is why I rated them best overall instead of honorable mention. This is best for adventurers who don’t want to carry a water purification filter that offers exceptional water treatment.

Product Specs
  • Active ingredient: Chlorine dioxide
  • Removes/destroys: Viruses, bacteria, and protozoa
  • Tablets per pack: 20 or 30
  • Tablets needed per liter: 1
  • Weight: 0.9 ounce
PROS

Easy to use; just pop a tab into a liter of water and wait

Doesn’t have horrid iodine taste like some other tablets

Lightweight

Fewer potential side effects than iodine or regular chlorine tablets

CONS

Have to wait considerable time to achieve safe drinkable water

Doesn’t filter out pesticides or industrial pollutants

Has an expiration date, so check!

Some users reported product caused scratchy/itchy throat

People have been using iodine to treat water for a long time. The problem is that the water treated with iodine turns a funky orange color and tastes like iodine, which tastes like crap.

While the Potable Aqua iodine tablets were the least expensive effective tablets I could find (almost half the cost of the Katadyn MP1), they do come with some significant drawbacks. First the pros: It’s the cheapest and it’s a killer of bacteria, viruses, and Giardia.

Now the cons: It doesn’t kill Crypto and can have some health impacts for some people. Iodine is a substance your body needs. That’s why they iodize salt. But in too high quantities, it can mess you up — so follow the directions closely. Iodine can also pose a health risk to pregnant women and people with thyroid issues. And some folks are allergic to iodine. It can also have some side effects like nausea or headaches.

Because it tastes funky, you’ll be psychologically less motivated to hydrate which can lead to other issues. To remedy the funky taste and color, Potable Aqua also offers PA Plus — which is an iodine neutralizer — with their iodine tablets for a few bucks more, but this adds an additional step, is another bottle to carry (doubles the weight), and still doesn’t kill Crypto. My take: The iodine tablets themselves are unpleasant. The neutralizer adds complexity and weight. Spend the extra few dollars and get the chlorine dioxide tablets.

Product Specs
  • Active ingredient: Tetraglycine hydroperiodide
  • Removes/destroys: Viruses, bacteria, and some protozoa
  • Tablets per pack: 50
  • Tablets needed per liter: 2
  • Weight: 3 ounces
PROS

Easy to use; just pop two tablets into a liter of water and wait

Fairly lightweight

Kills most creepy crawlies

Unopened bottles last up to 4 years

CONS

Have to wait 30 minutes to 4 hours to achieve drinkable water

Doesn’t kill Cryptosporidium

Doesn’t filter out pesticides or industrial pollutants

Has an expiration date, so check!

Turns water orangish color

Tastes terrible without additional neutralizer

Honorable Mention

There’s not much to differentiate the Aqua Pure chlorine dioxide tablets from the Katadyn MP1 tablets. They run on basically the same chemistry. Both have 6.4 percent sodium chlorite and one percent sodium dichloroisocyanurate as their active ingredients. I did find two distinctions: The Aqua Pure CD tablets are a dollar cheaper, and in my super unscientific research, fewer users reported scratchy throats from the Katadyn tablets, but take that with a grain of iodized salt.

With the MP1 tablets, Katadyn’s secret ingredient is Chlorine Dioxide and it controls all microorganisms and meets EPA microbiological water purifier test standards. They’re easy to use: You just add one tablet per liter of water to an opaque container and then wait 30 minutes to four hours — depending on the water quality — to achieve a 4ppm solution of Chlorine Dioxide in your water bottle. It’s effective against viruses and bacteria in 15 to 30 minutes, but in cold or dirty water, you’ll need four hours to kill Crypto. You won’t readily know the quality in the field, so to be really safe, you’re looking at four hours to drinkable water. You can risk drinking it earlier, but know that the more you deviate from instructions, the more you increase the risk of getting a bug that will blow your colon out past Saturn to Uranus.

The other thing to keep in mind is that no water tablet is going to filter out dirt, leaves, sticks, or any other organic matter in the water. You’ll have to do this by pouring the water through a coffee filter or clean bandanna. They also won’t neutralize chemicals like pesticides in runoff or industrial pollutants like lead, so you’re still fucked if that’s in the water. #ProTip: Don’t get water from streams near cow pastures or farm fields, for that matter. Go upstream.

Product Specs
  • Active ingredient: Chlorine dioxide
  • Removes/destroys: Viruses, bacteria, and protozoa
  • Tablets per pack: 30 or 20
  • Tablets needed per liter: 1
  • Weight: 0.9 ounce
PROS

Easy to use; just pop a tab into a liter of water and wait

Doesn’t have terrible iodine taste like some other tablets

Lightweight

Fewer potential side effects than chlorine or iodine tablets

Packaging is durable; knife recommended to open

Five-year shelf life

CONS

Have to wait considerable time to achieve drinkable water

Doesn’t filter out pesticides or industrial pollutants

Has an expiration date, so check!

If you are concerned about ingesting chlorine or iodine, or your body reacts poorly to them, Purzine drops are worth a look. They’re made with natural ionized sulfate mineral salts and reduces and inactivates biological and some chemical contaminants including bacteria, viruses, protozoa, pesticides, herbicides, fungicides, heavy metals, pharmaceutical drugs, disinfectants, disinfection byproducts, VOCs, and more.

Purzine works through the process of reduction oxidation (REDOX) and coagulation flocculation (CF). Taking you back to high school chemistry class, REDOX converts hazardous contaminants into less toxic compounds that are less mobile or inert through electron transfer. CF removes suspended pollutants by clumping them together to form particulates that can be strained through a coffee filter or fine cloth. Purzine’s website offers a nice explanation.

The manufacturer states the wait time is 60 minutes for safe water and one to 48 hours for any particulates to settle depending on the water temperature (colder = slower, warmer = faster). It’s pretty easy to use; just add the recommended amount of drops to your canteen, shake, and wait 60 minutes. It does not have an expiration date. Since it’s 97.5 percent water, you might want to make sure to carry it next to your body and not let it freeze in winter conditions. I like the simplicity, but it’s a slower process than chlorine dioxide. While CD will kill most viruses and bacteria in 15 to 30 mins, Purzine takes 60 minutes. And while CD will kill Cryptosporidium in four hours, Purzine takes 24 hours.

Product Specs
  • Active ingredient: 2.5% sulfate mineral salts
  • Removes/destroys: Viruses, bacteria, and protozoa
  • Volume: 2 ounces, larger units available
  • Drops per liter: 20, treats 15 gallons
  • Weight: 2.4 ounces
PROS

Easy to use; just pop the top, drop drops, and wait an hour

Doesn’t have terrible iodine taste

Fairly lightweight

Natural

Unlimited shelf life if properly stored

CONS

Have to wait considerable time to achieve drinkable water

Much slower to kill Crypto; up to 24 hours

Best Two-Part Drop Treatment

I know more than a few folks who swear by Aquamira’s drop treatment. It’s a Part A and Part B system. Part A is the neutralizer which consists of a two percent aqueous solution of chlorine dioxide which, like the tablets, kills viruses, bacteria, and protozoa. For one liter of water, you’ll have to put seven drops of Part A into a mixing cap and then add seven drops of Part B and let the mixture activate for five minutes. The solution will turn fluorescent yellow. Then you’ll dump the solution from the mixing cap into your canteen, shake, and wait 15 to 30 minutes.

This product doesn’t discolor water like iodine or give off an unpleasant taste. I love that it’s lightweight and easy to use, but still prefer the tablets for their simplicity. When I’m fatigued in the backcountry, I don’t want to have to fiddle around counting drops from two different bottles. This is an effective system, but not as simple as tablets.

Product Specs
  • Active ingredient: Chlorine dioxide
  • Removes/destroys: Viruses, bacteria, and protozoa
  • Volume: 1 ounce, larger units available
  • Drops per liter: 14 (7 Part A and 7 Part B), treats 30 gallons
  • Weight: 3 ounces
PROS

Effective against viruses and bacteria in 15 to 30 minutes, kills Crypto within in 4 hours

Doesn’t have terrible iodine taste

Lightweight

Long shelf life

CONS

Fiddly mixing of two different solutions

Bulkier than tablets

More complicated treatment process

If you are one of those folks who believes Mil-Spec is the best stuff, then you might want to check out Chlor-Floc. This water treatment was developed for sale to the U.S. Army and has its own NSN (NSN# 6850-01-582-5270). It comes in powder form and uses aluminum sulfate and troclosene sodium dihydrate to kill pathogens.

The yellow on black branding reminds me of the (insert skill here) For Dummies book series — which makes perfect sense for the Army. Make no mistake, this is military-grade water purification powder that eliminates giardia and most bacteria and viruses. The truly cool thing is that it works fast (one minute to shake, three minutes to wait, 30 seconds to swirl, and then seven to 15 minutes to wait depending if your water is warm or cold), and it helps eliminate sediment from your water.

The “floc” in Chlor-Floc has to do with flocculation — a chemical process that helps all sediment in fluid settle at the bottom. So it doesn’t remove sediment, it just puts it at the bottom where you’re least likely to drink it — unless you’re a grunt. They’ll probably drink that, too. Each box comes with 30 sachets that will treat a total of eight gallons of water. Each packet treats one liter. The downside? It has a shorter shelf life (three years) than CD tablets and has a slight aftertaste. The whole aesthetic of this product is ideal for preppers and tacti-cool dudes.

Product Specs
  • Active ingredient: 2.5% sodium dichloro-s-triazinetrione dihydrate
  • Removes/destroys: Viruses, bacteria, and protozoa
  • Volume: 1 ounce, larger units available
  • Drops per liter: 14 (7 Part A and 7 Part B), treats 30 gallons
  • Weight: 3 ounces
PROS

Effective against viruses, bacteria, and Giardia (not Crypto though!)

Tolerable aftertaste

Lightweight

Fast-acting

Designed to reduce sediment

CONS

Still need to strain through a bandanna or filter to truly remove sediment

Doesn’t kill Cryptosporidium (bummer)

What to consider when buying water purification tablets

Most water purification tablets come in three general categories: chlorine, chlorine dioxide, and iodine. All are effective in killing viruses and bacteria, but some, like chlorine and iodine, struggle when confronted with Cryptosporidium and Giardia which gets KO’d in the first round by chlorine dioxide. 

Types of water purification tablets

Chlorine

These are old school tablets that are great for killing bacteria and viruses but are not effective against Cryptosporidium and have low effectiveness against Giardia — both of which are found in North America. They are sharper on the palate and leave your water with a noticeable yet bouncy swimming pool aftertaste.

Iodine

Iodine is another old-school and proven way to treat water. Like chlorine, it struggles against Crypto and is somewhat effective against Giardia. Iodine tablets leave your water looking orangish and are angular on the palate with a bright flavor of yuck and hints of gross and doctor’s office.

Chlorine dioxide

Think of these tablets as Chlorine 2.0. They’re highly effective against bacteria, viruses, and protozoa to include Crypto, and leave a faint swimming pool aftertaste more like your municipal water system — because it is used in some municipal water systems.

Key features of water purification tablets

Portability

Water purification tablets are the ultralightweight backpacker’s solution to water treatment. They’re super small, only weigh a few ounces, and can treat water on the go. 

Speed 

While tablets are lighter and smaller than water filtration systems, they are also slower — requiring about 15 to 30 minutes to kill bacteria and viruses and up to four to 24 hours to kill some protozoa. (With mechanical filtration, you can drink water immediately through the filter.) They take some planning to use on the move. #ProTip: Use two canteens when using tablets. Drink out of one that’s already been treated while the other is being treated and trade off. 

Health

Waterborne illnesses can be super unpleasant at best, and fatal at worst. The further you are from the trailhead, the greater your risk, so don’t fuck around with water sources. You should treat (or filter) any water you get from wild sources. I use either a Platypus GravityWorks or Katadyn BeFree water filter in the backcountry and always take tablets as a backup system.

Cost

Water tablets (or drops) are way cheaper than water filtration systems in the short term. For the most expensive tablet system I could find, you can treat 30L of water for about $16. The cheapest filter I’d trust my life to is the Sawyer Min and that runs about $22 and lasts three to five years. So the cost of entry with tablets is cheaper, but for a few dollars more, you can get a mechanical filtration system that does everything tablets do but will last for years and leave your water tasting much better. 

Pricing for water purification tablets 

There isn’t a whole lot of variation in water tablet pricing. The cheapest I could find that I’d recommend were the iodine tablets at $8, and the most expensive tablets I could find were the Katadyn chlorine dioxide tablets at $17.

Tips and tricks

  • When using tablets, because they take so long to work, use two canteens so you can drink treated water from the first canteen on the go while the second canteen is treating your water — then alternate. 
  • Pay attention to water temperature. Chemical treatments work faster in warm water than they do in cold water — almost twice as fast.
  • Bring along a clean bandanna or coffee filters to help strain out the chunks from your water.
  • Better yet, get your water from low turbidity sources if you can.

FAQs about water purification tablets

You’ve got questions, Task & Purpose has answers.

Q: How long do water purification tablets last?

A: They last until the expiration date, so check them. Most last a few years. 

Q: What is the best chemical to purify water?

A: Hands down, it’s chlorine dioxide because it nukes viruses, bacteria, Giardia, and Cryptosporidium.

Q: Does boiling water remove chlorine?

A: Yes, if you boil it for 15 to 20 minutes.

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