Backpacking Water Treatment Options

Stopping at a stream to filter some water.


 Recently, while hiking on the Appalachian Trail, my wife and I stopped at a river crossing to refill our water containers.  Another couple who we had run into on several occasions in the past few days had also stopped to do the same.  We noticed that they weren’t just filtering their water, but boiling it too.  They said that one of the AT shelter caretakers had told them that some cases of an unknown virus had made some hikers sick in the area and they should not only filter, but also boil the water they got anywhere in the following twenty miles or so.  Well, it was too late.  We had already started drinking the water.  Luckily, we didn’t get sick and were able to complete our section hike in good health.  I was not so lucky about 16 years ago while living in southern Mexico.  I picked up an amoeba and lived with amoebic dysentery off and on for about six months.  After dropping 50 lbs and taking countless deparasiting treatments, I was finally cured.  I don’t recommend it to anyone.


Most water filters that backpackers use these days are capable of removing many of the common waterborne microbes and parasites, depending on the filter.  When buying a water filter, it’s important to check the pore size of the filter.  Common sizes you will find range from 0.1 to 3 microns (micrometers) depending on the filter.  Also, check to see if it has a rating of absolute or nominal.  If a filter has a 0.2 micron size with an absolute rating, then it should filter any microbe 0.2 microns or above because all its’ pores are consistently 0.2 microns.  Another filter that has a 0.2 micron pore size with a nominal rating only has an average pour size of 0.2 microns and therefore, may allow some 0.2 micron organisms to pass through.  Below are some microbes that you may encounter on the trail and their size ranges.


Protozoa: Amoeba, Cryptosporidium, Giardia (1 – 15 microns)

Bacteria: E-coli, Cholera, Salmonella (0.2 – 5 microns)

Viruses: Hepatitis A, Norwalk Virus, Rota Virus (0.02 – 0.2 microns)

Filtering some water from a trickle out of a rock on the mountain side.


Some considerations when looking for a water source while backpacking.

  1. Flowing water is usually less contaminated and is almost always a better choice.


  1. Avoid small pools or puddles. If not possible, then draw water from below the surface in the cooler part of the puddle, but away from the bottom.  The mud or soil at the bottom is an excellent source of nutrients and provides nourishment to the microbes, aiding in their multiplication.


  1. Microbes tend to grow and proliferate in warm stagnant pools of water. If you know that stagnant water will be your only choice, then take a filter and purification tablets or a UV light.  After filtering your water, add purification tablets and allow enough time for them to work, or use your UV light.


  1. Beaver ponds can act as a source for Giardia and should be avoided.


  1. Avoid water by pastures with cattle, horses, or other livestock. Cryptosporidium and E. coli bacteria can be found on animal manure which can wash down into the water source.


  1. Many fields where crops are being grown or have grown can contain pesticides or fertilizers. Water sources in these areas should be avoided.


  1. Streams or rivers downstream or near mining areas, and large construction projects should be avoided. Mining run-off can transport heavy metals and acidic waste into water sources.  Very few practical water filters are effective against heavy metals.


Note: If you suspect that a virus is found in your water source and you don’t have tablets or a UV light, then boil the water 1 – 3 minutes, depending on your elevation.  The higher the elevation the longer the boil time.


Here are some of the best water filters and purification options available.


Pump-Type Filters:

  • Katadyn Hiker – Pleated 0.2 micron Glass fiber with Carbon Core, 11 ounces

  • Katadyn Hiker Pro – Pleated 0.2 micron Glass fiber with Carbon Core and Filter Protector, 11 ounces

  • Katadyn Vario – Pleated 0.2 micron Glass fiber and Ceramic Filter, 15 ounces

  • Katadyn Pocket – 0.2 micron Silver-impregnated Ceramic Element, 20 ounces



From right to left: Katadyn Vario Pump Filter, Sawyer Squeeze with pouch, and Katadyn Hiker Pump Filter


Gravity-type, Squeeze, and Straw Filters:

  • Sawyer Mini – 0.1 micron Hollow-Fiber Membrane, 2 ounces

  • Lifestraw – 0.2 micron Hollow-Fiber Membrane, 2 ounces, $20


Purification Tablets or Drops:

30 Pack:  0.9 ounces


Ultra Violet (UV) Light Treatment:

  • Steripen Ultra – Rechargeable, Up to 50 treatments per charge, 5 ounces


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One comment

  1. Thanks, great article.

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