Katadyn Micropur Chlorine Dioxide Tablets

Katadyn Micropur Chlorize Dioxide Tablets
Katadyn Micropur Chlorine Dioxide Tablets

Ultralight Water Purification

Up until this year, I have always carried Micropur chlorine dioxide tablets for water purification in my emergency repair kit, in case my 16 oz First Need water purifier crapped out on a backpacking trip. I even got to use them for a few days during my 100 mile wilderness trip last summer when my purifier clogged and I ripped a hose.

But when I went hiking across Scotland this spring, I left my First Need and a British inline purifier I’d started using recently behind, making the switch to chlorine dioxide tablets as my primary water purification method. (On hindsight, I should have further filtered my water after exposing it to chlorine dioxide using an ultralight filter like the Aquamira Frontier Pro which can remove cyrpto [see comment stream below].)

I did this to reduce pack volume and weight. This is a pretty significant change in my hydration system and preferences, but one I’m a lot more comfortable with as my backpacking experience level has evolved.

Water Filter and Purification Limitations

When it comes to water filtration or purification, there are no absolutes. Each method has it’s pluses and minuses depending on water temperature, turbidity, and local industrial or biological contaminants.

  • SteriPENS and chemical purifiers are less effective when your water has a lot of suspended solids.
  • Chemical purifiers take longer to work in very cold water and chlorine dioxide takes a full 4 hours to kill a hardy protozoa named cryptosporidium.
  • Boiling requires that you carry extra fuel, but works the best with snow.
  • Iodine tablets don’t kill cryptosporidium.
  • Filters that use activated carbon don’t remove viruses.
  • Pump based filters and purifiers are heavy to carry and are prone to cross-contamination.
  • Inline or gravity filters can be slow and require that you carry extra water, hosing and reservoirs.
  • Most methods, except a First Need purifier, don’t remove industrial pollutants or fertilizers
Lincoln Brook - White Mountains
Lincoln Brook – White Mountains

Chemical Water Purification

Most of the places I hike in New England have clear, low turbidity water supplies (streams, lakes, and springs) but there are protozoa and bacteria in the water supply, requiring backcountry water treatment. Chlorine dioxide tablets are an excellent lightweight alternative here for 3 season backpacking. I use Katadyn Micropur tablets, but Portable Aqua Chlorine Dioxide Tablets are also available.

Each Micropur tablet comes in its own waterproof foil compartment, 10 tablets per sheet. You need one tablet per quart (liter) of water or about 5-6 a day: a package of 30 tablets weighs under 1 oz, which is absurdly light

The tablets will crumble if smashed, so I pack them carefully because it’s easier to add the tablet to a bottle of water than powder, though the powder is no less effective.

The foil wrapped tablet compartments can be difficult to open by hand or with your teeth, so I open them with the small pair of scissors on my Victorinox Swiss Army Classic knife. I can’t hike without these scissors – there are useful in so many ways.

Comparable Chemical Water Purification Products

ProductActive IngredientVirusesBacteriaGiardiaCryptosporidium
Potable Aqua Iodine TabletsIodineYesYesNoNo
Potable Aqua Iodine and PA+ Plus TabletsIodineYesYesNoNo
Polar Pure Iodine CrystalsIodineYesYesNoNo
Potable Aqua CIO2 TabletsChlorine DioxideYesYesYesYes
Katdyn Micropur TabletsChlorine DioxideYesYesYesYes
Aquamira CIO2 LiquidChlorine DioxideYesYesYesYes
Aquamira CIO2 TabletsChlorine DioxideYesYesYesYes

Treatment Time and Effectiveness

Chlorine dioxide tablets take 30 minutes to kill a protozoa called giardia and bacteria but can take up to 4 hours (or longer) if your water is turbid with suspended particles or very cold. In such cases, boiling for a few minutes may be the only way to quickly purify it without a filter. Chlorine dioxide also kills a second common protozoa called cryptosporidium, but requires 4 hours of contact.

Cryptosporidium is widely distributed in the ecosystem and not waiting the 4 hours required to kill it is a risk. One way to mitigate this risk is to filter out cryptosporidium using a filter such as a 2 oz Aquamira Frontier Pro that is threaded to screw onto narrow necked plastic water bottles.

When using tablets, my routine runs like this: I try to drink 16-24 oz of water per hour in hot weather depending on my exertion level. That works out to about 1 quart (liter) every 2 hours. I carry a 1 quart recycled water bottle with a 2 or 3 quart platypus reservoir for camp or as a reserve if I need to carry more water between water sources.

If I’m only carrying a quart of water at a time, I finish the remaining water in my bottle when I come across a new water source, refill it, drop in a chlorine dioxide tablet, and make a mental note of the time. I carry my water bottle in an external mesh pocket on my backpack, where it will rapidly warm up if cold.  This system works well because I’m not thirsty, waiting for water to purify, after a refill.


Some people complain that water treated with Chlorine dioxide tablets tastes bad. To tell you the truth, I can’t taste any difference between it and normal bottled water. That makes sense, because the concentration of chlorine in bottled water or municipal tap water is the same. Adding an activated carbon filter like the Frontier Pro will improve the taste and further protect you against micro-beasties that require a longer exposure time to chemical purification.

Disclosure: The author owns this product and purchased it using their own funds.

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  1. Great, informative post!

  2. Great write-up! We frequently carry the liquid version of this (Aquamira)the only time we carry a filter now are on sections of trail where the springs are so low that "dipping" water out is difficult if not impossible.

  3. So the Chlorine Dioxide tablets can take between 30 min – 2 hours? Is this the fastest water purification solution? What if you need water fast

    • re: Adayak: Then you should have thought about that 30 min – 2 hours ago.

      But yeah, I wish it was faster. It would be nice to be able to use it on day hikes.

  4. They only take longer than 30 minutes if the water is very cold or full of suspended solids. If you want a faster purification solution, you need to explore another option or just carry more water with you.

  5. I remember a previous post of yours about the Aquaguard Eliminator purifier. I was looking for a gravity based system, and I saw the Aquaguard was UK only and hard to get. It turns out that a southern California based company called Seychelle, are the manufacturers of the Eliminator purifier for Aquaguard and you can get them from Seychelle.com for $29.99 US + shipping. This gravity based/in-line filter gets it all. Giardia, Crypto, bacteria, Viruses, most industrial metals and contaminants, and even anthrax. I have just started using this system and the flow is pretty good. I also carry either aquamira or micropur tabs as a backup.

  6. There's no really perfect solution. The chemicals are effective, but you can't see that they've worked, filters fail silently, UV lamps break, and boiling takes time and fuel. I've been using these pills for a while and still haven't had troubles. Back in the good ol' days, we just drank from the springs, but that probably was a bit risky.

    Actually most of the "beaver fever" people report is good old fashioned food poisoning due to poor sanitation on the pots and sharing things with people who are already sick.

    • Have a question I cannot find an answer to anywhere after reading ten gazillion articles. When combining both filters and tablets as recommended to be extremely safe, tablets in dirty water than filter, or filter first and tablets in clean water?

      Intuitively I can’t calculate the best way in my brain. I wouldn’t want the tablets interfering with the filter process, getting the chemicals into the filter and maybe doing some possible damage or residue left in it.

      Conversely, if I stick them in after, and I wont give the filter an opportunity to possibly make the water taste better as it has carbon also in it

      • Don’t know what the science says, but I’d have thought you would filter first then use tablets. The chlorine dioxide/chlorine in the tablets reacts with a wide range of contaminants, and would lose effectiveness if there were too many of them. By removing most contaminants first, you are reducing the amount of material the tablets have to react with, which should make them more effective at killing the little that is left in the water. If you don’t like the taste of chlorine dioxide, you could try a chlorine-based tablet.

      • Thanks. I can always filter, tablet, than carbon last.

  7. Squirrel – Nice find – they are the manufacturer and it is a great filter. Still tops for an inline in my book and the flow is good enough for drinking in a reservoir system. The UK product seems to come with quick connect adapters – see the original article (linked in your comment). Not sure if you can get these in the US too.

  8. Helen

    Those jpgs are not showing up – I get a not found.

    I'm not sure I agree with your spreadsheet – why is 30 minutes of purification with chlorine dioxide listed as unsafe? What is safe?

  9. Rob – excellent point. I haven't had any troubles either so their either working or I'm not showing any symptoms. Ah, a halting problem.

  10. I use Micropur too. I'm happy with the taste, but have always wondered if anyone else sees a yellow/green tinge to water treated with these tablets. (I asked the company if this is normal and they said that the product should not affect the water's color). Do you notice a color tinge when you treat your water?

  11. The greenish tint in from the water supply you are using not the chlorine dioxide. I noticed the same thing in the white mountains two weeks ago when I got water near the Bonds, but I've seen clear water and other tints in other locations.

  12. Earlylite, the Seychelle filter does come with the quick connect adapters as well as a faucet adapter for back washing. I was looking for a lightweight filter that I can fill and drink without waiting for chemical purification to work. Its all about planning, and I never go into a hike without chemical backup, but this system works for me.

  13. Uh – a ringer. This requires some more due diligence. Hold on….

  14. oh crap. ok – does crypto really take 4 hours to kill and how prevalent is it in New England? What about other places in the US>

  15. Here's info from the CDC, or organization I trust. http://www.cdc.gov/crypto/epi.html
    The upshot is that crypto is out there, although it might not be where you are and you may not become symptomatic. Symptoms can occur in 2 days of infection. The primary cause of contamination in thought to be cattle feces. A 4 hour treatment time is required in this case. Hike in Vermont and you are going to be wading through cows.

  16. Ha, you were foolish to doubt me. I used to read 'Morbidity and Mortality Weekly.' The kill rate on crypto depends on the species and innumerable other factors. Even then, they die in a bell-shaped distribution over time. But they are so virulent, we have to kill every last one of them in our potable water.

    ~ Crypto is everywhere mammals and reptiles poop, and all other places the wind can carry that fecal matter. Even though we have the best water system in the world, thousands of Americans are infected every year. There was a big outbreak in Upstate NY a while back. Crypto is a big, rugged organism that has adapted to surviving in harsh environments. That's why it is so hard to oxidize them, and so easy to filter them.

    ~ The point of my spreadsheet was to highlight the absence of a royal road to safe water. All methods have serious problems for backpackers. My device is optimized for backpacking, because I put more effort into keeping it light, convenient, and reliable.

    • So once you get crypto, does it die on its own over time, or is it like AIDS, once you have it…

      And…. Be a mite more specific. You said the “kill rate” and ” it dies in a bell shaped curve”

      What does, Crypto or the PATIENT!!!

  17. I am chagrined to admit that I knew about the crypto issue but forgot about . I'm going

    1) abridge the post

    2) carry a Frontier Pro and screw it on my bottles when I want a drink. I'm still going to use the chemicals for purifying water when I fill my bottles and overnight in a reservoir (for the 4 hour wait time) and not use a hose system.

    I'm glad I studied your spreadsheet and that we're having this conversation.

  18. That's what friends are for, right? There is way too much disinfo online about water disinfection. And it starts at the top, with the manufacturers concealing the limits of their products. All this is a symptom of the very difficult problem backpackers have with foraging and treating water.

    ~ Self-publishing substantial material is very difficult. That's why writers don't strangle their editors. Tempting though.

    ~ I've amended the spreadsheet to reflect my discovery that Aquamira drops don't even pretend to kill crypto. Shame on McNett for burying that fact.

    ~ Visiting Upper Antelope Canyon, our Diné guide tried to teach me the tribal name of this spectacular site. I asked him if it was considered to be a traditionally sacred place. He laughed. The name means "sewer pipe." I'm sure that prehistoric reverence for high places had a lot to do with their sources of clean water.

  19. Helen,

    I'm a little slow this evening; the product in the image is the Aquamira Frontier Pro?

  20. Hi Andrew.

    ~ No, the Aquamira filter is designed with a mouthpiece for drinking directly from a bottle. Combined with their tablets, you get solid protection from the full spectrum of bugs with 30 minutes of contact. It won't connect to hoses.

    ~ The blue filter I showed was the Platypus CleanStream. It must be used with hoses, though they can be very short. This filter flows so freely, it doesn't need head pressure from a long hanging hose. A hydration hose can even be teed into the clean side for those who need instant and effortless hydration.


    ~ Squirrel's Seychelle filter also plugs into hoses. It's a composite device probably including activated charcoal and silver ions, which would be very useful with tannin colored water.

  21. George Phoenix

    Here is a great Youtube video that inspired me to use this sort of system:

    Enjoy and be safe!

  22. Jason (his video) and I worked together with Brian Green on testing this exact system last year. We found that setting up a gravity filter system with the Frontier Pro doesn't work consistently for everyone. YMMV, but for me gravity filtering with a Frontier Pro proved to be glacial despite the fact that I tried it with 4 different Frontier Pro filters. The only way I can reliably get water out of a Frontier Pro is by using the mouthpiece and sucking it through.

    The real value of this video for me, is how Jason cut down an old bladder to use as a scoop for collecting water from shallow water sources. I made one of these for myself and use it all the time. It's a great idea.

  23. George Phoenix

    It's absolutely slow if relying on gravity alone, but I squeeze the "dirty" bag to get the water through. You have to let the air out of the "clean" bag at some point to reduce back pressure but this has worked fine for me.

    I think I'm going to try tablets instead of Aquamira drops my next time out. More expensive but less fuss.

  24. thanks for the info. Using the tabs in the bottle you drink from, is there any problems with the cap or threads staying dirty?

  25. That's a very insightful question. There would be a problem if I drank straight from the mouth of the bottle. But I always buy water bottles with a plastic nipple (what do you call those things?) that opens when raised and closes when pushed down. I have to keep the mouthpiece clean of course, but that's pretty easy and I can always re-purify it with Purell.

  26. A good discussion. World Health Organization has some good information on water treatment.

    I will stick to my Combi pump. I have boiling a few chlorine tablets as backup.

  27. I used my Frontier Pro again last weekend and remember why I don't like it. When you suck on the mouthpiece you need to chomp down with your teeth. That triggers TMJ for me. So, I've ordered two purifiers from Seychelle.com: the advanced straw and their advanced push top bottle. I already own their inline purifier and love it, but these look way lighter and I wouldn't need a reservoir system to use them. They're both EPA registered and filter out 99.9999% of everything bad. I'll do a review in a few weeks after I get to use them on a backpacking trip.

  28. After much looking (the info is on neither the packaging nor on the Aquamira website), I finally found on the McNett website that the Aquamira Frontier Pro filter is 3 microns. Per the CDC website, 1.0 microns is the maximum filter size recommended for both giardia cysts and crypto cysts. Makes me wonder if the Frontier Pro isn't a complete waste of time and money. I, too, found that as a gravity filter it took forever–15-20 minutes per liter. By comparison, the late lamented ULA Amigo Pro filter does a liter in 2-3 minutes.

  29. So you want to treat the water with the tablets first, and than filter the water. Correct?

  30. Louie October 4, 2015 at 6:42 am #
    Have a question I cannot find an answer to anywhere after reading ten gazillion articles. When combining both filters and tablets as recommended to be extremely safe, tablets in dirty water than filter, or filter first and tablets in clean water?

    Intuitively I can’t calculate the best way in my brain. I wouldn’t want the tablets interfering with the filter process, getting the chemicals into the filter and maybe doing some possible damage or residue left in it.

    Conversely, if I stick them in after, and I wont give the filter an opportunity to possibly make the water taste better as it has carbon also in it


    • The tablets will work best if they have less biological matter to disinfect, so filtering then tablets would probably be best in most scenarios. Plus the tablets take time.

      Would you scoop up the water, disinfect for the requisite length of time, then filter? Or would you filter right away, then drop the tablets in and let them work while you’re on the move? I think the latter makes a lot more sense.

      Plus this way I think you have fewer chances for cross-contamination provided you’ve used everything correctly. The tablets will disinfect your drinking water container.

  31. Sawyer mini is .01 so I SHOULD be safe to the whole spectrum. But adding in chloride dioxide tablets at the end should solidify the whole deal :)

    • I’ve always used just the Sawyer mini with no tablets. I don’t adore water anyway so I hate the idea of making the taste even worse. Haven’t gotten sick yet but maybe I’m just lucky.

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