The 5 Best Water Purification Tablets

© John Barker

In this post, we’re discussing the how’s, when’s, and why’s of using water purification tablets, along with sizing up five of the best water purification tablets available today.

Between filtering, boiling, UV radiating, and chemically altering, there are plenty of ways to treat contaminated water in the backcountry—and lots of discussion about which method is best.

Though water purification tablets may not always rank high on the list, they are a valuable survival item to have in your pack in case you find yourself low on drinkable water, or in an emergency situation.

Tablets are the most common form that water purification chemicals come in, but they are also available in powders or drops.

What Are Water Purification Tablets?

WHAT ARE THEY FOR?

There are many situations where water tablets can come in handy, and they can be used on all kinds of biologically contaminated water whether it’s collected from swamps, rivers, lakes, etc. Depending on the water’s turbidity, it may require a larger chemical dose. Tablets do not, however, treat “toxic water” that’s been altered by pesticides, mines, or any sort of chemical contamination.

For most casual hiking or backpacking trips though, the majority of tablets should work just fine. 

Water treatment pills are good for camping, as a backup plan on long treks into remote locations, or for use to purify water sources following a natural disaster. They’re also not a bad thing just to have on hand for emergencies. 

HOW DID THEY COME ABOUT?

Growing concerns about water safety came into play in the 1800s during a major cholera outbreak in London. Years later, a British scientist named John Snow linked the disease spread to polluted drinking water. From there, he went on to figure out that chlorine could be safely added to water systems to act as a bacterial disinfectant.

Snow’s theory spread worldwide in the early 1900s and chlorine began being used as a water sterilization method throughout major cities. Then, in the 1940s Harvard University developed the first portable water treatment tablets. They were originally created for use by the U.S. Army and given to soldiers to carry in their packs for sterilizing water during emergencies. Since then, water purifying tablets have been tweaked and refined, bringing us the large variety we currently have today.

HOW DO THEY WORK?

Even when a stream, river, or lake appears crystal-clear, it can still contain heaps of dangerous microorganisms that when ingested bring on a slew of gastro issues like diarrhea, vomiting, or in more serious cases, illnesses that can even lead to death. This is why it’s important that any water collected from an untreated source first be sterilized before drinking it.

Although it may sound odd to hear the words “chemicals” and “drinking water” paired together in a positive light, tablets contain a safe amount of chemicals that when dropped in water dissolve and go to work on “killing off” dangerous microorganisms like bacteria and viruses, making the water safe for human consumption.

ARE THEY EFFECTIVE?

Water purification pills can eliminate harmful water threats like viruses and bacteria, including common gut destroyers like E. coli, Salmonella and Cholera. However, it’s important to note that tablets DON’T eliminate chemical pollutants, sediment, or certain protozoans.

How strong a tablet is and what it protects against will depend on its chemical makeup. For example, chlorine dioxide tablets are effective against Cryptosporidium, but a scientific study performed by the Department of Soil, Water and Environmental Science at the University of Arizona in Tucson proved that iodine tablets are ineffective in safely deactivating Cryptosporidium.

The water’s temperature along with its pH level is another consideration, as these factors can alter the effectiveness of a tablet.

Common Types of Water Purification Tablets

Ingredients-wise there are three main chemicals used to make tablets: iodine, chlorine, and chlorine dioxide. These chemicals are the most effective in killing off harmful pathogens while remaining safe for human consumption.

Below are a few notable details about the three common chemicals used in water treatment tablets: 

Iodine:

• Fights bacteria, viruses, Giardia.

• Works best in warm water, as Iodine’s effectiveness slows down in cold water and it’ll take longer to disinfect.

• The amount of Iodine needed to purify water changes depending on how contaminated or cloudy the water is.

• Iodine leaves a strong, rust-like aftertaste.

Chlorine (Bleach):

• Fights bacteria, viruses, Giardia.

• Works better in a pill than in liquid form because of the additional sodium-based ingredients.

• Will work in a large assortment of pH levels.

• Strong chemical smell and aftertaste

• Water treated with chlorine shouldn’t be left in storage or it can lead to recontamination.

Chlorine Dioxide:

• Fights bacteria, viruses, parasites, Cryptosporidium, Giardia.

• Requires a longer treatment time.

• Though slightly more expensive than the other two chemicals, chlorine dioxide kills a greater range of microorganisms, making it the superior choice in water treatment options.

• Doesn’t leave much of an aftertaste.

Note: Since different water treatment tablets offer different levels of protection, you’ll want to read the fine print on the packaging and do some research into the area you’ll be traveling to get a better idea of its water contamination level. Knowing these facts ahead of time and even checking in with local rangers or other sources in the area, can help zero in on the best tablet for your trip.

Tablets vs. Other Purification Methods

Bottom line: should you using water purification tablets for your water purification needs?

✅ WEIGHT: ULTRALIGHT

Tablets take minimal space in your pack and weigh as little as a fifth of an ounce. To put that in perspective, a Sawyer filter and a Steripen weigh 2 and 5 ounces, respectively.

✅ SHELF-LIFE: LONG

Unopened, purification tablets have a shelf-life of approximately 5 years.

✅ COST: CHEAPER UP-FRONT

When compared to filters, water purification tablets are a cheaper up-front option. Why up-front? Tablets are single-use while other purification methods will filter hundreds of gallons of water before needing to be replaced.

✅ EASE OF USE: SIMPLE AS 1-2-3

Besides a container to hold the water in, they don’t require any special equipment, additional fuel for heating, or electricity. Drop 'em in and wait.

❌ LONG-TERM USE: NOT DESIGNED FOR CONTINUOUS USAGE

Tablets shouldn’t be a long-term solution to treating water, as their chemical make-up is safe in small quantities, but isn’t intended for extended use (like over six months).

❌ TASTE: OFTEN GIVES OFF A CHEMICAL TASTE

Another downfall to tablets is how they give off a strong chemical smell and flavor, especially the chlorine and iodine ones. Note this can lessen by letting the water “air out” during treatment or by using an iodine neutralizing pill.

❌ PREP TIME: ABOUT 30 MIN. OF WAITING TIME

Compared to filters, tablets don’t offer immediate clean water like a filter can, since adequate time is needed for them to do their work. Just know that they don’t provide immediate results, and you’ll have to wait anywhere from 30 minutes-4 hours when using them for water to become safely drinkable.

❌ EFFECTIVENESS: NOT AS PURE AS OTHER METHODS

Another consideration is that according to the CDC, out of the various ways of sterilizing water, boiling remains the most effective in removing harmful pathogens. Filters are also known to provide the “cleanest” tasting water, and they block dirt and debris without having to pre-filter the water, which is a necessity with tablets.

Taste neutralizing tablets take about 3 minutes to take effect. 

How to Use

STEP-BY-STEP:

1. First, make sure you have a clean container to store your water in.

2. After you’ve gathered the water, do your best to strain it before adding the tablets as this will get out the excess dirt and debris. Either running it through a clean cloth, coffee filter, paper towel, or a bandana will work.

3. Read through the instructions on the packaging, and measure out the amount of water that can be sanitized per tablet (or tablets.)

4. Drop in the recommended number of tablets.

5. Place the cap loosely on your water container, and swoosh the water around so it reaches every area, including the lid.

6. Wait around five minutes or so.

7. Then (with the cap on, but still a little loose), give the container a good shake to again cleanse the entire inside of the bottle, including the screw threads near the cap!

8. Set the bottle down and wait for the recommended time. This can range between 30 mins-4 hours, depending on the tablet and your circumstances.

9. You can wait with the bottle cap on or off. If using a chlorine-based tablet, having the cap off can help to “air out” the chemical taste and smell.

10. After the time’s up, you’re good to go! Drink up!

Fizzing vs dissolving water purification tablets (Left: Potable | Right: Coghlan's)

Best Water Purification Tablets:

Aquamira

Cost: $10.99

Amount: 20 tablets per pack

Time: 30-min for Bacteria, Viruses, Giardia, 4-hours Cryptosporidium

Type: Chlorine-dioxide

Protects against: Bacteria, Viruses, Cryptosporidium, Giardia

A strong and trusted option, each Aquamira tablet purifies up to one liter of water and is registered with the EPA as being a safe solution in water purification. The tablets come in a small resealable foil pouch that weighs .7 oz. When you first open the pouch, you’ll notice a chemical smell, but this tones down in the water after some time and it doesn’t leave a lingering chemical aftertaste. Being a chlorine-dioxide based tablet they protect against Cryptosporidium and Giardia, which is said to lead to upwards of 80% of waterborne illnesses.

Potable

Cost: $10

Amount: 30 tablets for cholrine dioxide, 50 tablets for iodine

Time: 30 mins for iodine tablets, 4 hours for chlorine dioxide tablets

Type: Tetraglycine Hydroperiodide, Chlorine Dioxide option available (which treats Cryptosporidium)

Protects against: Bacteria, Viruses, Giardia Lamblia

Potable is a trusted brand that’s used by the military and worldwide emergency organizations like the WHO (World Health Organization). When using the Chlorine Dioxide tablets, which protect against Cryptosporidium, one pill purifies one liter of water. Potable also offers a 30-minute iodine-based tablet that comes in either a single bottle purification option or a two-bottle pack. The two-bottle pack includes a water treatment pill and a PA+Plus neutralizing tablet to improve the iodine’s taste and color. The Chlorine option comes in a foil pouch, while the Iodine tablets are in small glass bottles. Unopened, they have a shelf-life of around five years.

Katadyn Micropur MP1

Cost: $12.50

Amount: 20 tablets per pack

Time: 15-min for bacteria/viruses, 30-min for Giardia, 4 hours for Cryptosporidium

Type: Chlorine-dioxide

Protects against: Viruses, bacteria, Giardia, and Cryptosporidium

A powerful tablet made from one of America’s leading water-filter companies, this is a proven reliable option for water treatment. A single tablet will purify up to one liter of water, no matter the water’s condition. There’s not a lingering aftertaste and the tablets will improve any funky odors too, making Katadyn one of the best tasting brands on our list. The tablets are also EPA registered in meeting the standard of safe microbiological water purifiers. Each pill comes in individual foil packaging and has a 5-year shelf-life.

Coghlan’s Germicidal Tablets

Cost: $12

Amount: 50 tablets per bottle

Time: 30 minutes

Type: Iodine-based

Protects against: Bacteria, Viruses, Giardia

Coghlan’s, a camping, RV, and outdoor accessory company created this water purification pill for short-term emergency use only. It takes two pills to treat up to one quart of water, making the entire bottle capable of providing 25 quarts of total drinkable water. For being an iodine-based option, there’s still not much of a lingering aftertaste. The tablets have a four-year shelf life, but be sure to keep the bottle sealed when not in use, as exposure to moisture or humidity can alter the tablets’ effectiveness. This option does not protect against Cryptosporidium cysts.

Aquatabs

Cost: $10

Amount: 30 pills per pack

Time: 30-40 minutes

Type: Sodium Dichloroisocyanurate (a form of chlorine)

Protects against: Bacteria, Viruses, Protozoa, Giardia cysts

Trusted by Aid Agencies around the world, a single tablet can treat up to two quarts of water if it’s relatively clean, .8 quarts if less so. Each tablet is individually packaged and Aquatabs offers a variety of sizes that are suitable for treating various amounts of water. Taste-wise, they leave a faint hint of a chlorine aftertaste and smell. Each pack has a shelf life of five years, and Aquatabs claims their pills are safe for long-term use. The product’s minimal packaging is a bit of a bust, lacking in-depth instructions and details about the tablets, but their website provides more headway information-wise (read up before your trip!) They do not protect against Cryptosporidium.

FAQ

Are water purification tablets safe?

When used properly, tablets are generally safe. They should be used sparingly, however, and not as the main source of acquiring clean water for months on end. Iodine pills can be especially dangerous when used for long periods, and they shouldn’t be taken by women who are pregnant or anyone with iodine sensitivities or thyroid issues.

What are the risks?

As long as you’re buying from a reputable company and the pills are taken properly and in small amounts, you’ll be good. The pills should never be swallowed whole, and they should be handled with care when being used, as the chemical residue left on hands can irritate eyes and skin causing a burning or itching sensation.

Lastly, if you’ve never used tablets before, the chemicals in them may cause mild stomach, mouth, and throat irritation upon the first few uses, although, this doesn’t happen for everyone. 

What do water purification tablets taste like?

Water purification tablets will vary in taste depending on the type of chemical used.

Iodine, for example, gives off a more metallic flavor, and it can even turn your water (and your water bottle) a rusty hue.

Chlorine can have a strong chemical flavor and give off an unpleasant bleach smell. This can be reduced by letting the water ventilate for a while.

Chlorine Dioxide is a chemical that remains rather flavorless. Some users even say they think it improves the taste of water.

Do water purification tablets expire?

Most tablets have a long shelf life, lasting months or even years depending on the brand and packaging.

To ensure this long shelf, it’s best to store them in a safe, dry place when not in use, and when using a bottle be sure to recap the bottle tightly. Naturally, individually wrapped tablets will have a longer expiration date compared to a bottle once it’s been opened.

Once a bottle has been opened it’s recommended the pills be used within three months.