I Examined the 5 Finest Water Purification Tablets

If you’ve ever struggled with a clogged-up water filter, the advantages of water purification tablets are self-evident. Just drop in a tab, let it do its thing for 30 minutes, and your water is ready to drink. But not all drops work the same way, and knowing which has the longest shelf life or the least noticeable aftertaste can help ensure you’re properly equipped for your next backcountry adventure or natural disaster. To help you choose, I tested the best water purification tablets and assessed them on a number of key metrics.

How I Tested the Best Water Purification Tablets

While I typically use one of the best backpacking water filters when out in the backcountry, I’ve also turned to water purification tablets for their convenience and small packed size. I have first-hand experience with all of the below water purifiers, many of which I have used in backcountry settings. 

I assessed the water purification tablets in this story for both emergency and backcountry use. For emergency use, I primarily considered price and shelf life, in addition to taste, ease of use, and whether they are effective against bacteria, protozoa, viruses. For backcountry use, I also considered the time to treat a liter of water. Price was evaluated as the cost to treat a liter of water assuming you purchased the water purification tablets in the most cost-efficient bulk option. 

Best Water Purification Tablets: Reviews & Recommendations

Best Overall: Aquamira

Key Features

• Cost to Treat a Liter of Water: 50 cents
• Shelf Life: 4 years
• Taste: Good

Pros

• Fastest of the water purification tablets
• Virtually no taste

Cons

• Comparably expensive
• Process is a little more involved

Aquamira treatment drops have long been a favorite of backpackers and backpack hunters who’d rather not deal with the hassle of water filters at all, including OL staff writer Tyler Freel. (See: What’s Best for Backcountry Water: Filters or Drops?) And I can see why: While those of us that use filters are hunched over and red-faced, squeezing out a liter of water from a sketchy pond, Team Aquamira just has to wait 20 minutes, the least of any of the water purification tablets I looked at. Even better, it has very little taste. I personally can’t taste it at all, although others say there is a slight aftertaste. 

Of course, there is a catch, and it’s that the process to use Aquamira is comparatively onerous. There are two bottles, Part A and Part B. When mixed together, they produce chlorine dioxide, which is reactive in water, breaking the bonds that hold bacteria, protozoa, and viruses together. To use Aquamira you mix together seven drops of Part A with seven drops of Part B in the larger of the two caps. After five minutes, you can add the mixture to a liter of water. 25 minutes after that, your water will be safe to drink. Note: You cannot pre-mix parts A and B before you head out on your trek. It must be done in the field right before you treat your water.

If you’ve been burned by water filters in the past, then Aquamira is a reliable alternative that requires little elbow grease. Its comparatively long shelf life and limited taste also makes it a reasonable choice for home emergency kits where you want to make sure the family actually stays hydrated for the duration. 

Best for Backpacking: Aquatabs

Key Features

• Cost to Treat a Liter of Water: 12.5 cents
• Shelf Life: 5 years
• Taste: Fair

Pros

• Extremely lightweight
• Inexpensive

Cons

• Noticeable taste
• Not effective against cryptosporidium

Aquatabs take about 30 minutes to take effect, 10 minutes longer than Aquamira, but are much easier to use. Simply drop the tab in the water and wait. No premixing required. But while Aquamira has no discernible flavor, there is a slight chemical flavor that goes along with the Aquatabs (although not as unpalatable a flavor as straight chlorine or iodine). 

While this is only a minor concern in a true survival scenario, the off-putting flavor of Aquatabs can affect how hydrated you are in the field if you aren’t careful about it. After all, who wants to drink water that tastes like a swimming pool? One solution is to add other flavor mixers (like Mio drops or Crystal Light packets) to your water to mask the taste. Per liter of water, Aquatabs are about a quarter of the cost of Aquamira, making them a smart choice for backpackers on a budget. 

Best for Home Emergencies: Katadyn Micropur

Key Features

• Cost to Treat a Liter of Water: 53 cents
• Shelf Life: 5 years
• Taste: Fair

Pros

• 5-year shelf life
• Effective against cryptosporidium

Cons

• Most expensive option I looked at
• Takes 4 hours to be effective
• Noticeable aftertaste

Natural disasters can be a stressful time, because typically not only are you dealing with the loss of power and potable water, but potentially also access to certain emergency services. This is not the time to get diarrhea. So I was impressed to see that Katadyn Micropur was effective against cryptosporidium, even if it took four hours for it to get there. 

While the Katadyn Micropur is promoted for outdoor use, the 4-hour activation period makes it a better choice for home emergencies. 

That length of time makes it a non-starter for backcountry use, but it is a reasonable choice for use in home emergency settings, where it is reasonable to be treating one batch of water while consuming a second that has already been treated. It also isn’t as complicated to use as Aquamira (which is also able to neutralize cryptosporidium if left for four hours to treat). 

The downside to Katadyn Micropur is that it was, by a hair, the most expensive option per liter of use. 

Best Shelf Life: Potable Aqua

Key Features

• Cost to Treat a Liter of Water: 43 cents
• Shelf Life: No expiration date if unopened
• Taste: Bad

Pros

• Unopened containers can be stored indefinitely
• Easy to use

Cons

• Terrible taste
• Long-term use can cause issues with your thyroid or even cancer

It used to be that “water purification tablets” meant one thing: iodine. It was a standard in backpacking kits of yore (especially when the old pump filter models were less reliable than they are now), but I always dreaded having to pull it out. Not only does iodine taste terrible, but it also lingers. Whatever Nalgene you used to treat your water would permanently smell like iodine. Granted, these days, you can purchase iodine tablets that neutralize the taste, but I’d still think twice before adding these to your backpacking kit. That’s because the other problem with iodine is that, when taken in larger quantities for long periods of time, it can cause issues with your thyroid or even cancer. Current recommendations are that you stick to about a milligram a day. Potable aqua contains about 8 milligrams per tablet.

But there is one situation where potable aqua is still your best bet: if you are packing up an emergency kit that you don’t plan on refreshing periodically. Potable aqua, if unopened, has an indefinite shelf life, making it the only option on this list that is safe to crack open a decade from now and add to your water.  

Best Budget: Household Bleach

Key Features

• Cost to Treat a Liter of Water: 0.05 cents
• Shelf Life: 1 year
• Taste: Poor

Pros

• Widely available
• Very cost effective

Cons

• Noticeable, off-putting taste
• Shorter shelf life

The first person I ever met who used bleach as their primary method of purifying their water was a nurse on the Pacific Crest Trail. While everyone else was struggling with backed-up squeeze filters or carefully mixing their Aquamira solutions, she simply pulled out a small bottle of chlorine and a medicine dropper. We watched her add a couple of drops to her bottle and be on her way while we were still messing around trying to get our Steripen to work. This, she reminded us, was how most municipalities disinfect their water. It’s also extremely cheap compared to other water purification tablets. Given these pros, you might be wondering why all backpackers aren’t out there using chlorine to disinfect their water.

Well, first off, most people find the taste to be pretty off-putting. After 1,000 miles or so, the thru-hiking nurse said she’d stopped noticing the taste, but I could smell it coming off her bottle. Also, there is a reason that the idea of using chlorine in your bottle is giving you the heebie-jeebies: You have to add enough chlorine to disinfect your water, but adding too much can lead to chlorine poisoning, including burning in the mouth, stomach pain, and vomiting. Also, there is some debate as to whether or not using chlorine in the water supply can increase your long-term risk of cancer, with some suggesting that it can lead to an increase in bladder cancer. (If this has got you wondering about what’s coming out of the tap, consider picking up one of the best filtered water bottles.) 

If you are going to use chlorine to disinfect your water during a backcountry or emergency situation, be sure to acquaint yourself with the EPA’s guidelines on how much to use. 

How to Choose the Best Water Purification Tablets

Shelf Life

If you’re purchasing water purification tablets for a home emergency kit, keep a sharp eye on the shelf life. While some water purification tablets do last indefinitely if unopened (like iodine), others have a shelf life of five years or less. 

Cost

If you’re purchasing water purification tablets for an overnight backpacking trip, then the cost per unit is typically insignificant against your other costs. But if you’re planning a thru-hike or for a week-long emergency kit for the whole family, it can start to add up. 

Taste

The taste difference between different water purification tablets is wide, from no taste at all to so foul it’s hard to drink it. Consider how important taste is to you (as this can have an effect on your ability to keep yourself hydrated) before making a final choice.

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Final Thoughts

Whether you are looking for an alternative to the best backpacking water filter or planning your home emergency kit, there are a variety of water purification tablets available. Consider your priorities, be it price, taste, shelf life, or active ingredient, before making a final purchase.