The Truth About Water Purification In a Survival Situation

This post may contain affiliate links so I get a commission if you purchase through the link.Thank you! Please read the disclosure for more info.


You can’t drink that crystal clear water! I know we’ve all hiked by a pristine lake, river, or stream and thought, “Boy, that water looks pure! I bet it tastes great!”

That water may have a couple really nasty micro-organisms that will make you very sick.

Those organisms may be:

  • Protozoa like Cryptosporidium or Giardia.
  • Bacteria like E. coli.
  • Viruses like Hepatitis A, rotavirus, enterovirus, norovirus.

The symptoms can be debilitating when you are in a survival situation. The symptoms vary but generally you can expect:

  • Diarrhea
  • Vomiting
  • Gas
  • Intestinal discomfort
  • Even death in some cases

If you are just out camping and will be going home, then the whole experience can be embarrassing, inconvenient, and expensive.

That water is crystal clear but you should think twice before drinking it.

However, if you are in a survival situation and can’t get to an ER, doctor, or hospital, then the impact can be very severe. The situation can get bad very quickly and you may find yourself extremely weak. It is likely that dehydration will follow – making you even more thirsty.

One thing to note: The symptoms often show up after several days up to a few weeks. So if you are very thirsty and know that you MUST drink water to survive then you should do it. You will have to understand the consequences and weigh the risks.

There are four main ways to purify water so you can drink it from the wilderness.


This is a simple method – just bring the water to a rolling boil for a one minute. If you are at a high altitude, the boiling temperature is lower so you should boil the water longer.


  • Boiling does not change the flavor.
  • If you are camping or have the gear to cook then you should have the right gear to boil.


  • Boiling uses fuel.
  • You can’t boil water on the move.
  • You have to wait for the water to cool.
  • You can only boil small batches.

Water Purification with Filters
Check out the Katadyn Vario Dual Technology MicroFilter at Amazon.

Filters are highly effective and now that big outdoor stores carry so many options, they are economic too. They work by literally filtering out the micro-organisms. Nearly all filters will remove giardia and cryptosporidium, and parasitic eggs and larvae, but it takes a pore-size of less than 0.4 microns to filter the bacteria.


  • Can filter bacteria.
  • Does not impact the flavor.
  • Will normally filter from 200 to 1000 gallons depending on the model and filter.
  • Cloudy and murky water can be treated.


  • Few filters can filter out viruses.
  • The filter cartridges need to be replaced periodically.
  • Filters are mechanical and are subject to failure.
  • Maintenance is required to keep the filter in good working order.


Water Purification with Chemicals

Check out the Potable Aqua Water Purification Treatment (50 Tablets) at Amazon.

Two primary chemicals are used: Chlorine dioxide and Iodine. Both come in tablet form commonly and the iodine may come in crystal form also. Both take about 15 minutes to treat the water at normal temperatures. If the water is very cold, it may take up to 4 hours to treat the water.


  • Light and easy to carry.
  • Easy to use.


  • The taste is greatly impacted.
  • Pregnant women and people with thyroid conditions should not use iodine.
  • It can take a long time to treat the water if it is very cold.

UV Treatment

Water Purification with UV TreatmentsCheck out the SteriPEN Water Purification System at Amazon.

UV treatment is a new-comer to the water purifying game. It takes about 90 seconds per 32 ounces to treat the water. The UV devices work best with clear water – if the water is cloudy or murky, then experts advise you to double the exposure.


  • It is a relatively fast way to treat the water, about 90 seconds.
  • The flavor of the water is not impacted.


  • Batteries are required.
  • The devices are more fragile than the other ways.


What method is the best to purify your water? Only you can decide…

You should think about each of the methods and the advantages and disadvantages. When you are faced with a challenging situation where you need to treat your water, you decrease your chances of getting sick.

Personally, I have multiple options since you need to be flexible in a survival situation. You might need to treat murky, almost muddy water, so the filtering system may be the best option especially over the UV treatment wand. Sometimes boiling will be the better option when you have a fire burning and plenty of fuel.

The Boy Scouts have it right, Be Prepared.


Here is a good video outlining backcountry and wilderness water and hydration. And, REI has a great resource page too.

Photo credit: Gordon B.

Meet the Author

'Mountain Man' John

'Mountain Man' John is a Survival and Preparedness enthusiast who loves everything outdoors. He has a passion for learning anything and everything to help sustain his and his families way of life post SHTF. He frequently shares his knowledge on a variety of topics from his hands on DIY projects, learning new skills such as hunting and trapping along with reviews on his Survival related purchases - Prepping has been in his family for generations, it's in his blood.