Water Purification: Survival Filtration

Some day, you may find yourself out camping or in the wilderness without any modern forms of water filtration and treatment. This does not mean you have to remain dehydrated. A survivalist water filter will clean the water sufficiently for short-term consumption. However, it is still possible that a few pathogens or bacteria will remain in the water after using these survivalist techniques, which is why you should only attempt them in a true  emergency.

In general, you have two options for purifying water in survivalist situations- boiling and making your own water filter. A combination of the two methods will produce the cleanest water.

Look for pure water sources

Before you filter or boil water, look for a pure source. Look for water features, such as:

  • Running water from a river or stream
  • Clear water
  • Sources away from roads, farms, cities, and other man-made locations
  • Water free of animal waste, dead plant debris, and dead animals

Building your own survivalist filter

Since it is nearly impossible to find fresh drinkable water in the United States, you will probably have to build a filter to strain out mud, tree branches, and other particles from the water. The easiest way to do this is with a sand filter.

If you have a plastic bottle or metal can handy, you can use that as the container for the filter. Otherwise, you will have to fashion a cone shape from bark or large leaves. Birch bark is ideal. Punch holes in the bottom of the plastic or metal container.

Fill the very bottom of the container with a 1-2 inch layer of small pebbles. You can also use non-poisonous grass or moss. Place a 3-5 inch layer of gravel over the pebbles. Fill the rest of the container with sand. If you have any charcoal leftover from a fire, place a 1-inch layer between the gravel and sand. Another filter recipe alternates layers of grass, sand, and charcoal. Use what you have on hand.

Pour water through the container and allow it to drip into another container. Keep filtering the water until it comes out completely clear on the other side. After filtering the water, boil it for safety. Boil the water for at least 10 minutes to remove as many pathogens, bacteria, and viruses from the water as possible.

Filtering water survivalist-style is not ideal. It is still possible to develop health issues from impure water using this filtering and purification method. However, a survivalist filter will produce cleaner water than simply drinking from a natural source, and you will have a much lower chance of injuring your body from impure water or dehydration.

What kinds of survivalist filters have you tried?


Water Purification: Sanitizing

If you remember, from part 1 of this series, the CDC recommends both filtering and sanitizing water to remove the highest number of contaminants, bacteria, and viruses from the water.

If you do not choose to filter the water before sanitizing it, the source of the water that you choose is extremely important. Look for clear water sources free of mud, contaminants, and visible signs of problems. A running water source is best.

Water far away from roads, fields, and other marks of civilization will contain the least amount of pathogens and chemicals.

Choosing the Right Sanitizer

When it comes to water sanitizers, there are a variety of options. In general, you can choose between UV filters, chlorine, and iodine. All of these sanitizers are effective at removing bacteria, but not all of them can remove viruses from the water.

UV filters

SteriPEN SidewinderUV filters only work well with pre-filtered water. UV filters are effective at killing pathogens from back country water. Most UV systems work by sanitizing and killing bacteria through focused UV lights, much like UV filters kill unwanted bacteria in homes and hospitals. SteriPEN®, produced by Hydro-Photon, Inc., is the most recognizable brand. They have several models — most battery operated — but the Sidewinder is especially interesting since it’s crank operated so no worries about those long expeditions.

Chlorine Tablets or Drops

Chlorine tablets or drops are effective at killing most bacteria present in water. If the water source is clear, there is less need for pre-filtering. Adding 16 drops of bleach or one tablet to a gallon of water will kill most of the bacteria in the water. Allow the mixture to stand for at least 30 minutes before drinking. If using tablets check the manufacture’s directions for treatment time. The problem with bleach is that it cannot remove chemical impurities from water.

Iodine Tablets or Drops

Iodine tablets are an inexpensive and lightweight method of water purification. Just like bleach, the mixture must sit at least 30 minutes before the water is safe to drink. Check the directions included with the tablets to be certain of treatment time. Iodine kills most organisms present in back country water. However, some protozoa are resistant to iodine, and iodine can often add an unpleasant taste to the water. Some tablets will be sold with a companion tablet which can be added after treatment to remove the Iodine taste. Follow the manufacture’s timing instructions to the letter as treating with the second tablet to soon can make the Iodine treatment in-effective.

Boiling Water

Camp Fire

The most old-fashioned form of water sanitation is boiling. Surprisingly, boiling water is one of the most effective sanitation methods. All pathogens will die through boiling, including viruses. The water must boil for at least a full minute at sea level — altitudes can affect this time though so boil for at least 3 minutes to be safe. Unfortunately, boiling water is extremely time consuming, requires  fuel to bring the water to the necessary temperature, and a container capable of withstanding high heat. Boiling water usually works well at base camp, but can prove a big pain while on the trail.

Many adventurers decide not to worry about viruses, especially if in the USA, and focus mostly on filtration methods to knock out any bacterial or protozoa. But to be certain you’ve covered all the possible contaminants use a multi-step approach of filtration and sanitizers.

Next time, we’ll discuss filtering water in survival situations without the help of modern filters and sanitizers.

What techniques do you use for sanitizing water while camping?

MSR MiniWorks EX Microfilter

I’m doing some research on micro filters in preparation for some hiking / camping trips planed for 2013. If funds allow, the MSR® MiniWorks® EX is one I intended to pickup and field test — I’ll update this post with my experiences. In the mean time, here are some reviews that have convinced me this model is one to try. If you’ve used the MiniWorks EX, please share your thoughts in the comments section below.

Made in the USAThe founders of Cascade Designs® setup shop in 1972 to produce Therm-A-Rest® sleeping pads. By 1991 they had released the first MSR® water filter, the WaterWorks®. Today we’re looking at the WaterWorks grandkid, the MiniWorks® EX Microfilter.


Weight 1 lb / 456 g
Width 2.75 in / 7 cm
Length 7.5 in / 19 cm
Filter media Ceramic Plus Carbon
Filter pore size 0.2 microns
Flow (L/min) 1 liters per min
Flow (strokes per liter) 85
Cartridge life ~2000 liters
Cartridge replacement indicator Yes

More Info


Worth every penny!

November 8, 2009 By R. Zamudio from Amazon.com

[editor’s note: Corrected some spelling errors. Possibly the best review I’ve ever seen on Amazon and a major factor in my decision to try this filter.]

I researched filtration systems for almost a month before settling on the MSR miniworks. I figured I could just go pick one up at the local Cabela’s or REI, but BOTH retail stores were sold out of these, while there was still a good supply of the other MSR and Katadyn filter systems on the shelf. I took this as a sign that this is the filter to have and ordered it from Amazon, and it has been worth every penny. Read on….


MSR MiniWorks EX


In Camp:
The filter is very simple to use and has a good output-per-pump ratio. You never really feel like you are doing more work than you should for the amount of water you are pushing through, especially if you take into account the fact that every pump is worth about one gulp of nasty water that you WON’T have to drink. If you do see a diminished output, simply unscrew the filter housing and give the element a light scrubbing. We were taking water from a brown lake that is loaded with tannins and we would get about 2 liters through (about 2 full-size nalgene bottles worth) before we noticed the filter could use a cleaning. Tannin-loaded water is supposedly some of the worst for clogging these ceramic filters, so if you have cleaner water sources at your site than we do, your element-cleaning cycles should be farther apart. The water came out crystal-clear and almost tasteless. It didn’t taste like Dasani bottled water, but it definitely didn’t taste like tea-colored lake water either. Pretty much neutral. More importantly, it tasted CLEAN and nobody got sick. Also, the MSR Miniworks requires no chemical additives but still claims to filter everything but viruses. The chance of contracting a waterborne virus from a U.S. lake or stream (think Polio, Hep-A, SARS, and a few others which you have probably had vaccinations for) is far lower than getting sick from bacteria or parasites. If this still bothers you, you can still boil your clear, clean-tasting water just to be sure.

Out of Camp:
The maintenance on this filter is very simple. The unit breaks down into 4 major parts, and the wrist pins on the pump assembly are quick-release squeeze-and-push types. You can literally have this thing stripped down and cleaned completely in about 5 minutes, and that includes the sterilization of the filter element. A couple dabs of silicone grease or chap stick is all you need to lube it up when you are reassembling the unit.

The Hidden Bonus:
$80 may seem like a lot for a water filter, but the MSR miniworks pays you back exponentially…
Prior to buying a filtration system, everyone in our backpacking party hauled their own water needed for the entire trip. We would calculate what we needed for hydration and cooking each day, plus a bit more just in case, and we strictly stuck to these rations. We would have enough water, but never enough to truly quench one’s thirst. Having this filter in our party allowed us to drop about 15 lbs carried, per person! Plus, we didn’t have to pack out a bunch of empty water bottles anymore. One filter supports 4 of us and we now drink as much as we want. When you think about how important hydration is to your body’s systems (Read Cody Lundin’s “98.6 Degrees” book and you will know more about the subject than you ever wanted to), shelling out $80 to have clean, safe water on-demand anywhere you can find a water source is a small price to pay.

-Put a coffee filter over the hose inlet and secure it with a twist-tie, rubber band, or fishing line. This will make your MSR filter pump more efficiently for longer without as-frequent element cleaning. Every time you clean the element, you are scrubbing away some of the element’s overall diameter. When it gets too thin, you have to get a new element. Fewer cleaning cycles = prolonged filter life and more money remains in your pocket. Filter element, $40. Coffee filter, 3 to 4 cents.

-Bring a spare filter element if you are going on an extended trip or are going to be absolutely dependent on this filter for your drinking water while you are out! Meaning: hiking back to your vehicle and driving like a madman to the nearest 7-11 for a drink before you go into a coma from dehydration is not going to be an option! The word is, these ceramic elements are fragile. Finding this out at the wrong time and being caught without a spare would be a very bad thing. If you spent the cash for the filter and other people in your party use it, have them pony up the $40 and buy the spare element for you. It’s only fair…. right?

-USE A NALGENE BOTTLE WITH THIS UNIT (or other similar one that will attach to the adapter). The motion created while you are pumping is far too violent for precision-aiming the output stream into any loose container, except for a bucket. You can also attach another length of rubber hose to the outlet and run that to your container, but we have not tried this yet. The Nalgene bottle seemed like the simple solution to use with the filter and we filled our other containers from this bottle.

{Product use update} – Our party of 3 did a 4-day back country hike in the Grand Canyon (search: Tanner Trail) this past winter. This is definitely NOT a tourist trail, and the first 2000-3000 ft of elevation is not much a trail at all. The noted only water source along this entire route is at the very bottom of the canyon, the Colorado River. We were able to augment our hike-in water supply by searching for pools of water trapped in depressions of the rocks near the places where we made camp, and pumping water from them using the MSR Miniworks. I don’t even want to think of what was in those water pools, but what came through the filter was clean and refreshing. We made notes of the larger water pools, which allowed us to lighten our water load on the hike-out and stop by the pools for a top-off when we needed it.