Water Purification: Particle Filters

The modern camper has a wealth of resources for staying healthy while anywhere in the world. Water is an essential part of camping, and if you do not want to lug heavy bottles of water around, you must invest in some type of  water filtration or sanitation system while camping. According to the Center for Disease Control, boiling is the best option. However, a combination of filtration and sanitization is the second best form of water purification.

When choosing water to use for drinking, the source is important. Look for running water, such as from a stream or river. Avoid water with algae or in stagnant ponds and lakes. Stay away from water found near roads or agricultural fields. This water can have harmful pesticides or chemicals and contaminants like tar.

The modern camper has many choices when it comes to water purification.

  • Boiling
  • Filtration
  • Sanitization


Done correctly, boiling kills off Protozoa and viruses and will always be the safest method of purifying your water. To properly boil water bring it to a rolling boil for one minute. Remember, at altitudes greater than 6,562 feet (greater than 2,000 meters), you should boil water for 3 minutes. I usually play it safe and boil for three minutes no mater where I’m located.

But, boiling isn’t always convenient. That’s why human kind has invented the portable water filter.

Camping with Filters

MSR MiniWorks EXFilters are mechanical purifiers, removing particles and contaminants from water by forcing the liquid through a porous material, physically blocking the contaminates. Filter material can be glass, ceramic and charcoal; many filter units use a combination.

Which type of filter you choose depends on the type of bug you want to remove. Bacteria can be filtered with a particle size of 0.4 microns or less. While a filter with a one micron rating will remove protozoa, like Cryptosporidium or Giardia, eggs, and larvae as well.  So rule of thumb, purchase a filter with the smallest micron rating you can afford. Check out the MiniWorks® EX from MSR®, it’s one of our favorites.

Viruses on the other had can’t be filtered and must be handled with a chemical disinfectant. More on those in our second post in this series.

Look for a model that weighs less than 20 ounces, is easy to use, and simple to clean. Units that offer a warning sign when the filter is at capacity can also help keep you safe while camping. A filter that is at full capacity can leech unwanted bacteria and contaminants into the water, risking your health. Depending on how many people are camping, the flow rate of the filter is also important. An average flow rate of one liter per minute is enough for a few campers, but if you have a larger group, you will want a greater flow-rate. Large gravity filters are ideal for larger groups.

Filtration pros: Effective at removing common water contaminants, lightweight,
inexpensive, and easy to use.

Filtration cons: Can be hard to locate new filters, may not eliminate all bacteria and
viruses, can clog and fail.

Look for part two in the water purification series soon!

What filter is currently in your pack?

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?

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?