Protozoa, such as cryptosporidium and Giardia, are relatively large and easy to filter out. They are thick shelled and hard to kill.

Bacteria, such as salmonella and cholera, are smaller than protozoa and harder to remove.

Viruses, such as hepatitis A and B, are the tiniest of all. Until now only boiling or chemicals could neutralize viruses. The Sawyer® Water Purifier will trap viruses without adding harmful chemicals to the water. Note: For viruses to be present at least one of the following conditions is usually present in the water:

1. Human or animal waste in the water 2. Dead animals in the water 3. Slow or stagnant water 4. Water temperatures above 50 degrees F If possible you should check with local authorities as to the water quality in the area to which you are traveling.

Filters and Purifiers
Filters trap protozoa and bacteria and prevent them passing through to you. Purifiers handle viruses which are too tiny for most filters. The Sawyer® Water Purifier is the only filter to trap viruses as well as protozoa and bacteria.

Ultraviolet Light
Rather than filtering, an ultraviolet light source is used to irradiate the water, which will neutralize pathogens of all sizes. Disadvantages include the need to carry extra batteries, dwell/wait times, and it’s ineffectiveness in water that contains any particulate. Unless the pathogen is in direct contact with the UV it will not neutralize it.

Oxidant Purifiers
This method requires a shorter contact time than iodine and works against cryptosporidium, as well as bacteria and viruses. The disadvantages include cost, replacement batteries, long wait/dwell times before you can drink the water, and the ingestion of chemicals into your body.

Boiling
Very effective, but you have to bring extra fuel and use your stove to prepare drinking water. There is also the waiting time for the water to boil and then cool enough to drink.

Chemical Treatments
Iodine and chlorine are lightweight ways to treat bacteria and viruses, but are not very effective against cryptosporidium. They add taste to the water and there are health risks with ingesting these chemicals. Long dwell/wait times are needed for this method to be effective. The colder the water, the longer it will take to work.

Ceramic
Can be brushed clean many times. Disadvantages include very expensive, can break easily—leaving you with no safe filtration, and relatively small surface requires frequent cleaning which requires disassembly of the unit-very time consuming.

Glass-Fiber
These non-woven surfaces are effective for Protozoa and Bacteria, but are too porous for viruses. Disadvantages include small surface area, and the inability to clean. So they clog quickly and then are useless.

Structured Matrix
This relies on static charge to get parasite to “cling” to surface area. Disadvantages include not knowing when all sites are “blinded” and harmful organisms are getting through.

Iodinated Resin
When used in main filter will kill organisms if ample dwell time is allowed. If water is drunk directly from the bottle then not enough time is present to neutralize viruses or other pathogens. The iodine is absorbed into the body and the pathogens remain viable. No indication when iodine resin is used up or is no longer effective.

Carbon
Used to remove organic chemicals such as chlorine. Will remove herbicides and pesticides if ample dwell time is given. It is most effective used to remove chlorine in household applications.

Hollow Fiber Membrane (HFM)
Very thin hollow porous tubes with uniform pore sizes. They offer a very large surface area in a very small volume. The pore size can be controlled to the extent that virus removal is possible. Due to the very large surface it will not foul quickly and gives ample warning before it plugs. It will not fail and will not allow pathogens to pass through.


The Sawyer® filter is the only filter on the market that effectively removes viruses without adding harmful chemicals to the water. Additionally, the Sawyer® HFM filter can be back-washed to greatly extend its life using the Sawyer® Faucet Adapter or a soft canteen if you need to back-wash in the field.

How does the Sawyer Water Filter compare to other methods?
Unlike oxidant purifiers the Sawyer® filter adds no chemical to the water, there is no waiting before you can drink the water, there are no batteries to replace and no spare batteries to carry, and the filter weighs a fraction of the weight of the oxidant purifiers.

Unlike the boiling method, the Sawyer® filter gives instant pure water without the wait for the water to boil or the expenditure of fuel required to boil the water. The Sawyer® filter weighs about the same amount as the fuel required to boil much less than 1 gallon of water.

Unlike chemical treatments, the Sawyer® filter gives instant pure water and does not add harmful chemicals to the water. Iodine is believed to be associated with thyroid problems and chlorine is associated with cancer risk. Iodine and chlorine also require long dwell times—up to four hours.

Unlike Ultraviolet light, the Sawyer® filter can give you pathogen free water regardless of the turbidity of the water. If they ‘hide” behind turbidity in the water they will not be neutralized.

How does the Sawyer Water Filter compare to other filter media?
It is lighter than ceramic filters, will not clog as quickly, is not fragile, and water flows more quickly through it.

It will last far longer than glass-fiber filter and is a fraction of its weight.

It is lighter than structure matrix filters and never leaves a question on whether the filter has expired.

It does not add harmful chemicals to the water which are absorbed by your body, like the iodinated resins do.

It has a uniform pore size that can reach the sub micron level unlike the carbon filters.