7 Ways to Purify and Filter River Water (and Some That Won’t Work)

If you find yourself in the wild, be it on a hike or a hunting trip, it’s always smart to bring at least one water purification system with you. You never know when disaster will strike and you’ll have to drink river water.

To avoid getting sick, you should always purify river water before you drink it. These seven methods are the best methods of river water purification.

1. Water Filters

A water filter (also known as a water purifier) is the most effective way to purify water, provided you buy a high-quality filter.

These handy devices are designed to remove bacteria, viruses, and chemical impurities from water, leaving you with clean drinking water.

Survival water filters are easy to come by, they don’t take too much room in the pack, and you can always rely on them to get the job done.

One thing people don’t like about water filters is that the good ones can come at quite a high price, while the cheap ones aren’t good enough. Personally, I’d pay a hefty price if that guarantees I’ll have drinkable water in the wild.


  • Safest way to purify river water
  • Ideal for large groups because of the large filter capacity
  • Removes all bacteria, viruses, and chemical impurities


  • More expensive than any other method

2. Boiling Water

The second-best method of water purification, endorsed by the US National Park Service, is boiling water. This will kill parasites, bacteria, and viruses.

Before you boil your water, however, you should filter it. If you don’t have a filter with you, you’ll have to improvise one.

A good sediment filter will catch sand, tiny rocks, or wood and leaf debris. These impurities are too large for boiling water to affect them, which is why you have to get rid of them before you boil water.

Boiling time depends on your elevation. If it’s below 6500 feet, boil your water for one minute. If it’s above 6500 feet, boil the water for at least three minutes.

In case you’re not sure about your elevation, boil the water for three minutes just to make sure it’s clean.

There are two downsides to boiling water. First of all, this won’t remove chemical impurities. If the water source is contaminated, boiling the water won’t make it safe to drink.

Second, boiling water over a campfire can take a lot of time, especially if you’re boiling water for an entire group. You also need to let it cool down before you can safely drink it.

Speaking from personal experience, it takes an eternity to boil water, and it takes just a few minutes for a group of thirsty people to empty the pot!


  • Kills all bacteria, parasites, and viruses
  • Cheap, requires minimal equipment
  • Very easy


  • Takes a lot of time (depending on the amount of water)
  • Doesn’t remove chemical impurities
  • Doesn’t remove large impurities, such as rocks or sand

3. DIY Activated Charcoal/Carbon Filter

DIY charcoal water filter
water filter” (CC BY 2.0) by ryochiji

Maybe you didn’t know this, but household water filters often use activated carbon (also known as activated charcoal) to purify water. You can do the same with river water. In fact, in the army, we were actually given activated carbon before every field task, and we were taught how to use it to make a water filter during our survival training.

Activated carbon draws in viruses, parasites, and bacteria, but it isn’t as effective as boiling, which is why I recommend you boil the water after filtering it. That way, you can be 100% certain the water is clean.

An upside of activated-carbon filtering is the removal of some toxic products. Tiny carbon particles can decompose toxic compounds, such as pesticides, into non-toxic products. However, water filtered through activated carbon needs to be used as soon as it’s done filtering because it will immediately start collecting impurities.

Making an activated carbon filtration system doesn’t require special equipment. All you need is a water bottle, some cloth, and activated charcoal. However, building this system isn’t as easy as boiling water, and you need to learn how to do it beforehand.

Note that this method is even slower than boiling water, and since you’ll be boiling the filtered water afterward, you’re in for quite the wait.


  • Removes almost all bacteria, viruses, and parasites
  • Removes some toxins, including pesticides
  • Completely purifies water in combination with boiling


  • Complicated setup
  • Slow filtration

4. Bleach (Chemical Disinfection)

Bleach is just one of the many compounds that can purify river water. Other compounds include chlorine dioxide and hydrogen peroxide, but they’re more difficult to get your hands on.

Before we move on with this topic, I need to point out three things:

  1. Bleach can kill you in large quantities. Be very, very careful if you’re purifying water with bleach.
  2. The method linked below does not apply to chlorine dioxide and hydrogen peroxide.
  3. If you’re purifying river water with bleach and you think you messed up, throw it all away and start from scratch.

Bleach purifies water through the use of sodium hypochlorite, which is a chlorine solution often used by big water systems for purification. Once you mix bleach with water, acid and oxygen will form. The oxygen will purify water.

This will remove all parasites, bacteria, and viruses from the water, but it won’t remove toxic chemicals. You’ll also have to wait a while before you can actually use the water!

You can find a step-by-step explanation here.


  • Just as effective as boiling
  • Purifies a lot of water with very little bleach


  • Very dangerous in large quantities (especially if you don’t know what you’re doing)
  • Takes at least half an hour
  • Doesn’t remove toxic chemical compounds

5. Disinfection Tablets

Also known as water purification tablets, these tablets are an easy way to purify river water. They can kill viruses, bacteria, and parasites (although that can vary from one tablet to another).

You don’t have to boil the water afterward, although I recommend it.

Disinfection tablets use chlorine or silver ions as the active ingredient. Silver ion tablets are particularly powerful, but they can take up to four hours to purify water, and long-term use can lead to the development of argyria. Argyria is a medical condition caused by the buildup of silver compounds, and it can result in permanent disfigurement.

They’re definitely a good option, but I wouldn’t rely on them for too long.


  • Quick and easy to use
  • Effective against viruses, bacteria, and parasites


  • Ineffective against toxic chemical compounds
  • Not safe long-term

6. UV Light Wands

A UV light wand is essentially a small water purifier. It purifies water by damaging the DNA of bacteria, viruses, and parasites in the water, making them as good as dead.

The good thing about this method is that it really works and it’s fairly quick in comparison to other methods.

The bad news? It doesn’t give you a whole lot of water because the wands themselves are small and it’s very expensive.

In my opinion, they’re too expensive for the amount of purified water they provide, and I’d rather buy a good water filter. Nonetheless, this is a valid water purification method in a pinch, and it deserves a mention.


  • Quick and easy
  • Works on bacteria, parasites, and viruses


  • Doesn’t work on toxic chemicals
  • Very expensive
  • Provides very little clean water

7. Filter Straws

Filter straws are relatively new products, and they’re similar to UV light wands, but they’re a better option if you ask me.

LifeStraw is one of the most popular filter straws, and it’s proven to work.

These straws eliminate almost all microbes from the water through their incredibly dense filters, which let water through and keep all microbes in the filter.

Filter straws are a great choice for one or two people but not for large groups of people. The filters have their limitations (1000 gallons for LifeStraw) and if a large group uses the same straw, they’ll use up the filter quickly.

Aside from that, however, filter straws are amazing devices for purifying river water.


  • Cheap
  • Very effective against microbes, dirt, and microplastics
  • Long lasting


  • Not intended for large groups
  • Ineffective against toxic chemical compounds

Effective Methods That Deserve a Mention

I’d like to mention four more methods of river water purification:

  • Ion exchange
  • Distillation
  • Reverse osmosis
  • Solar water purification

While these four methods are all very effective at purifying river water (especially reverse osmosis, which is listed by the CDC as the most effective water filtration method), they’re not really applicable in the wild.

All these methods require large, bulky systems that aren’t something you can just keep in your backpack. Some even require electricity. Because of this, I don’t think they’re good choices for purifying river water in the wild.

However, if you have a cabin in the woods and you’d like to try using the water from the river, I’d definitely recommend considering one of these four methods.

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