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)
Some considerations when looking for a water source while backpacking.
- Flowing water is usually less contaminated and is almost always a better choice.
- 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.
- 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.
- Beaver ponds can act as a source for Giardia and should be avoided.
- 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.
- Many fields where crops are being grown or have grown can contain pesticides or fertilizers. Water sources in these areas should be avoided.
- 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.
- 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
- MSR Guardian Purifier – 0.02 micron Advanced Hollow Fibers , 18 ounces
- MSR MiniWorks EX Microfilter – 0.2 micron Ceramic with Carbon Core, 15 ounces
Gravity-type, Squeeze, and Straw Filters:
- Sawyer Mini – 0.1 micron Hollow-Fiber Membrane, 2 ounces
- Sawyer Squeeze – 0.1 micron Hollow-Fiber Membrane, 3 ounces
- Lifestraw – 0.2 micron Hollow-Fiber Membrane, 2 ounces, $20
- Lifestraw Go Water Bottle – 0.2 micron Hollow Fiber Membrane with Activated Carbon, 8 ounces
- Katadyn Gravity Camp 6L – 0.2 micron Pleated Glass Fiber with Carbon Core and Filter Protector, 13 ounces
- Platypus GravityWorks Filter System – 0.2 micron Hollow fiber, 10 ounces
Purification Tablets or Drops:
30 Pack: 0.9 ounces
Ultra Violet (UV) Light Treatment:
- Steripen Adventurer Opti – Two disposable CR123 batteries, 4 ounces
- Steripen Ultra – Rechargeable, Up to 50 treatments per charge, 5 ounces