Jim:
In the interest of accuracy, I would like to clarify a couple of statements made by Kevin K. in his response to “The Water Filter Quest” submission. Kevin states: “Another problem with only using mechanical filtration is some viruses are physically impossible to filter out of water (i.e. rotavirus)” …. ” I know of at least one mechanical filter on the market that does in-fact filter out all known viruses and is used extensively in Third World missionary operations . Here is an excerpt from the filter manufacturer’s web site:
“The Sawyer 4 Liter 0.02 Micron Complete Water Purification System is critical to having adequate drinkable water when a crisis occurs… The 0.02 Micron Absolute inline water filter removes 99.99999% of all bacteria such as salmonella, cholera, E.coli, typhoid, amoebic dysentery, and streptococcus, and others, and also removes 99.9999% of all protozoa and cysts such as Giardia, Cryptosporidium, Cyclopora, and 99.9997% of viruses such as hepatitis A, hepatitis E, poliovirus, rotavirus, adenovirus and SARS (corona virus). These levels exceed the EPA guidelines by far, and equals or exceeds competitive options. If you are traveling internationally this filter is essential. Unlike other filtration systems, Sawyer offers a 1 Million Gallon Guarantee!! No more replacing the filter unit every few hundred gallons, just clean it and continue filtering. Whenever the flow rate slows, just back-wash the filter with clean water. Note that the filter does not remove minerals, metals, petroleum products or pesticides.”
It was also stated that: “As far as I understand it, carbon filters remove viruses as well, but the problem is you never really know when the carbon is “fullmaterial.” Carbon filters cannot filter out disease causing viruses or bacteria. Both are too small for the pores in the carbon and pass through without effect. However, carbon filters are excellent at filtering out some organic compounds, gases, odors, and bad tastes.
I have no financial interest in the Sawyer company and I own a number of other filters, but I can say hands-down that the Sawyer is the best gravity flow filter I have ever used. I can use it as both as a portable/ backpacking/ bugout/ unit or at a permanent location using two 5 gallon food grade buckets. Depending on the source water quality, I sometimes attach an in-line carbon filter after the Sawyer filter so I can get that “Evian” drinking water experience while roughing it. Best Regards, – Ron H.