There is a specific kind of optimism that makes people sick, one that echoes through eternity. At any time in human history, you can hear someone say, “Just drink the water, it looks fine.”
You are miles from the trailhead, your bottle has been empty for an hour, and there is a clear, burbling stream right there, looking like a commercial for itself. The water looks fine.
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That, dear friend, is exactly the problem. Some of the nastiest things living in water are invisible, tasteless, and perfectly happy to ride a gorgeous mountain stream straight into your guts, where they will spend the next two weeks teaching you a lesson about optimism.
This is the entire reason the water purification tablet exists in the first place. It is the lightest, cheapest safety net you can carry. A little foil-wrapped pill that turns probably fine into actually ok, it weighs nothing, and fits in a pocket of your pack until the day it saves your trip or your life.
A tablet only works, though, if you understand what it kills, what it absolutely won’t, and how long you have to wait while staring at a bottle and quietly dying of thirst. So let us get it right.
The Three Flavors
Every purification tablet runs on one of three chemistries, and despite what you may have read, they are not blended into a single super-pill. You pick one, and each has a personality.
Iodine is the old soldier of the bunch, the taste a whole lot of veterans can feel in the back of their throat just reading this. It handles bacteria and viruses well and, given enough time, takes care of Giardia, the parasite most likely to ambush a hiker. It also tastes like a mouthful of old pennies, and it comes with real strings attached that we will get to.
Chlorine tablets, like Aquatabs, are similar but different. They have similar strengths plus the faint flavor of a frequented hotel pool, minus some of iodine’s less desirable traits. Both are light, cheap, and have kept troops and travelers from having to use their socks and sleeves to wipe up after Montezuma’s Revenge for generations.
Chlorine dioxide is the major player in this genre, as well as the most important name on this list. It kills everything iodine and chlorine kill essentially, and it does the one critical thing the other two cannot. The price is patience, because it works on its own clock and asks for hours, not minutes.
The Catch
Iodine and chlorine do not reliably kill Cryptosporidium. Not with a double dose, not if you waited all afternoon.
According to the CDC, this particular parasite shrugs off both at any practical field concentration, because it comes wrapped in a tough shell built specifically to survive the chemicals we throw at it.
Crypto is neither rare nor gentle. It causes days to weeks of the kind of gastrointestinal misery that ends expeditions and lands people in hospitals. It thrives in exactly the backcountry and disaster water you are most likely to be treating.
Among tablet options, only chlorine dioxide handles it, and even then, the CDC says the safest move is to filter your water first.
There is no bulletproof answer or fancy new-fangled tech that can be reliably offered. Just as our little old ancestors figured out, a rolling boil for one minute or three minutes at or above 6,500 feet kills everything, Crypto included. When the stakes are real, and you have a fire, get to boiling.
When in Doubt
However, let’s say boiling is off the table, and a tablet is the plan. A few rules separate “treated” from “actually safe.”
If the H2O is cloudy, you’ll want to deal with that before the tablet ever touches it, because suspended sediment chemically neutralizes your disinfectant and gives germs places to hide. Pour the water through a bandana, a coffee filter, or a clean shirt first, or let it settle and draw off the clear water. Clear water treats, while murky water might give you the “bubble guts.”
Dose by the label, not by what your gut tells you. The instructions are calibrated to the amount you are treating; more is not necessarily better.
Once your tablet dissolves, wait the full time the manufacturer lists, then add extra time if the water is cold or cloudy, because cold slows down soldiers and chemical reactions to a crawl.
Chlorine dioxide tearing after Crypto can take up to four hours, so if that is your bug and your tablet, patience is truly a kingly virtue to have.
When the wait is genuinely over, and only then, you get to fix the taste. A pinch of powdered vitamin C or a crushed vitamin C tablet, stirred in after the contact time finishes, knocks out most of the iodine or chlorine flavor.
Add it early, and you neutralize the disinfectant before it has done its job, which defeats the entire point of standing there thirsty for half an hour.
Respect the hard limits, too. A tablet kills living things and nothing else. It does nothing about chemical contamination, industrial runoff, radioactive material, or saltwater. If your problem is poison rather than pathogens, no pill on earth makes that water drinkable, and you need a completely different plan.
The More You Know
Iodine is biologically active, so if you are pregnant, have thyroid problems, or might be allergic to it, skip iodine-treated water and reach for chlorine or chlorine dioxide instead.
Nobody should drink iodine-treated water for more than a few weeks straight, which makes it a fine emergency tool and a terrible daily habit. Frankly, that goes for all of them.
These are spare tires, not engines, and living on chemically treated water for the long haul becomes its own VA-disability-rated problem down the road.
None of this is meant to talk you out of carrying tablets. Carry them. They are the best few ounces of peace of mind you can stuff in a pack, and the day you actually need them, you will not give one thought to the taste.
Just respect them for what they are, a brilliant and limited tool that hands you safe water as long as you read the label, wait the wait, and remember the one bug they might miss.
So, carry your tablets, know their limitations, and when in doubt, always boil that sh*t.
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