pore field carbon weight pump L/min pumps filter
cost size clean? ? (oz)
force flow perL life
(micron)
(lbs) rate (gal) Pur Pioneer
$ 30 .5 no no
8.4 2 1.0 59
20
SwtWtr Walkabout $ 35 .2
yes yes 8.5
? .7 ? 100
Pur Hiker $ 55
.3 no yes 11.0
8 1.2 48 200
SwtWtr Guardian $ 60 .2
yes yes 11.0 2
1.0 60 200
MSR Miniworks $ 65 .3
yes yes 14.3 8.5
.6 100 1000
1st Need Deluxe $ 70 .1
no lots 15.0 6
1.7 45 100
Pur Voyageur $ 70 .3 + I
no yes 11.0 10
1.1 53 100
Pur Scout $ 80
1 + I yes option 12.0 11
1.0 60 200
SwtWtr Guardian+ $ 80 .2 + I yes
yes 15.0 3
.9 60 200,90
MSR Waterworks 2 $125 .2
yes yes 16.6 12
.8 76 1000
Pur Explorer $130 1 +
I self option 24.8 5
1.4 43 400
Katadyn Mini $139
.2 yes no
8.2 13 .5 120
1000
Katadyn Combi $185 .2 + I yes
yes 29.2 ?
1.2 50 14000,60
Katadyn PF $295
.2 yes no 22.7
20 .7 82 15000
Notes:
cost reflects lower of Campmor or REI retail price pore size must be < .3 micron to filter out small bacteria pumping force can increase considerably as filter clogs output rate can decrease substantially as filter clogs capacity as rated by manufacturer, might not be accurate models labeled "+I" use iodine to neutralize viruses and bacteria under filter life, numbers after comma indicate iodine longevity with silty water First Need clogs more rapidly than Pur Hiker MSR filters do not include cost of handy stainless steel screen Katadyn Mini requires frequent cleaning because of small size a huge pocket is required to hold Katadyn PF (pocket filter) only Explorer is self cleaning-- others require disassembly. Unpurified drinking water may contain four things that pose health risks: protozoan parasites (e.g. giardia), toxic bacteria, harmful viruses, and poisonous chemicals. Of the methods available in the field, only boiling and iodine are entirely effective against the first three, and only charcoal filtration is effective against the fourth. Because boiling and iodination take time, some folks prefer water filters, despite their weight. The Pur Explorer is recommended for large groups, and the Pur Scout for small groups. As of this writing, Pur filters are the only ones on the market that combine a filter (for giardia) with an iodine resin matrix (for bacteria and viruses). The Explorer ($130) is self-cleaning and very fast, while the Scout ($60) must be taken apart for cleaning, and is only half as fast. The MSR filter ($140) is also recommended, if viruses are not a concern. So far viruses are not a problem in most wilderness areas of the US, but they are a problem in the Himalayas and elsewhere. MSR filters are very convenient, since they can be screwed onto the top of your water bottle. The MSR's .1 micron final filter is small enough to remove bacteria, but if you travel abroad (to Nepal for example), you risk viral infections such as Hepatitis A and C, among others. The Katadyn water filter is expensive (over $240), and really has little to recommend it over the Pur or MSR filters. It must be taken apart for cleaning, like the Pur Scout. Its ceramic filter is subject to cracking if it freezes when wet. Perhaps its sole advantage is that you can scrub it almost forever, until the ceramic wears out, so it is favored by desert river runners. The Katadyn is effective at removing smaller bacteria such as E. coli, but its .2 micron filter is not effective against viruses. The First Need water filter is cheap ($40), but is not recommended, since some people have reported E. coli infections after using it. Its .4 micron filter pores are smaller than giardia cysts at 3.5 microns, but larger than some bacteria, such as E. coli at .3 to .9 microns. Optional charcoal filters are available for the Pur filters. For a limited time, they may help remove some poisonous chemicals, so they may be of use in agricultural areas. However, the charcoal also removes residual iodine, which may be needed to finish killing off high concentrations of waterborne bacteria and viruses. So use these charcoal filters sparingly. Some folks don't like carrying filters, and still don't mind boiling their water. To be entirely safe, water should be boiled at least five minutes. Giardia is killed in less than a minute at 176 F (80 C), well under the boiling point. Bacteria and viruses last longer, but are probably killed in less than five minutes at 190 F (88 C). Some types of virus may last longer; nobody knows for sure. At 10,000 feet water boils at 194 F (90 C); above this altitude boil water about an extra minute for each 1000 feet. Note that it's safe to make pasta using untreated water. If you have neither the time, nor the fuel, nor the inclination to boil, iodine is equally effective. After 15 minutes (30 minutes for cold water), a sufficient dose of iodine kills all bacteria and viruses. Some protozoa take longer to kill; studies have shown giardia lasting for several hours. Shaking your water bottle may help, but it's always best to wait longer. One readily-available choice is Potable-Aqua tablets. Dissolve one tablet per liter of water (two tablets for cloudy water) and wait. The problem with iodine tablets is that they degrade upon contact with moisture, so keep that bottle dry, and discard it upon returning home. Another choice is a bottle of PolarPure (elemental iodine). Add the number of capfulls recommended by the thermometer on the bottle. For travel in wet or humid areas, PolarPure is a better choice than Potable-Aqua. Avoid halazone and Clorox, because chlorine is volatile, slow to disinfect, and works differently against protozoa and viruses at various pH levels. It also reacts with organic compounds to form carcinogenic chloramines. Iodine is not highly toxic, and in fact is an essential ingredient of human nutrition. However, continuous ingestion of large doses may cause health problems, particularly for people with thyroid problems. The accepted concentration for iodine disinfection is 8 milligrams per liter, but this is mostly to get rid of protozoan parasites. A good way to reduce overall iodine consumption and minimize that iodine flavor is to filter first, then use a low concentration of iodine to get rid of bacteria and viruses. For this, a concentration of .5 mg/L is deemed adequate, so one capful of PolarPure or one Potable-Aqua tablet should disinfect around 16 liters of lightly filtered water. Various inexpensive ceramic filters with 1 micron pores are fine for removing protozoa. Giardia has become a well-known, almost fashionable, outdoor hazard. Many people who experience gastro-intestinal problems after drinking bad water think they have contracted giardia. In many cases they have contracted something else. Since the only FDA-approved treatment for giardia (Flagyl) is very nasty, it's wise to make sure you really have giardia before treatment. Most low-grade bacterial infections go away on their own, and Flagyl is ineffective against viral infections. One alternative to Flagyl is quinacrine. In many parts of the world (Asia for example) Tinidazole is also available, and is preferable to Flagyl since it is less toxic and quicker acting. [This information based on "Medicine for Mountaineering", various research articles, owner's pamphlets, and personal experience.] Addendum, info packet from manufacturer of Pur filters
"Three identical [Pur Traveller water filters] were evaluated for their
ability to inactivate/remove Klebsiella terrigena, poliovirus type1, rotavirus
SA-11, and Giardia lamblia cysts. The units were operated according
to the manufacturer's instructions until the designed lifetime of 100 gallons
(378 liters) passed through. The units were challenged with [the
micro-organisms mentioned above] after a passage of 0, 50, 75 and 100 gallons.
At the 75% lifetime challenge, 'worst case' water quality of 1500 mg/l
dissolved solids, 10 mg/l organic matter, 4 degrees C, with a turbidity
of 30 NTU and a pH of 9 was used. For the 100% lifetime test the
worst case water quality at pH 5 was used. The units were also tested
after stagnation for 48 hours at the 50%, 75%, and 100% [stages]. "At 0
and 50% lifetime test points, > 99.9999% of the bacteria, > 99.9% of the
Giardia cysts, and > 99.99% of the test viruses were removed. With
worst case water two passages of the test water through the units was required
to achieve these same removals. These units would comply with criteria
guidelines suggested by the US EPA... "One passage of the pH 9 worst case
water was not sufficient to remove the Klebsiella terrigena and poliovirus
type1 to the required reduction. However, the required reduction
[was] achieved by passage of the test water through the units a second
time... Holding the water for 5 to 10 minutes after it had passed
through the units also resulted in a further reduction of test bacteria
and viruses." Klebsiella terrigena is a bacteria that causes "stomach flu",
as can rotavirus SA-11. Here is the residual iodine after treatment:
cup1
cup2 cup3
0% .7 .7
.7 (ppm)
50% .6 .5
.6
75% .6 .6
.7
100% .7 .6
.8
This indicates that the filter still had plenty of life at 100 gallons. It also indicates that there is enough residual iodine to kill off all viruses and bacteria overnight (ppm = mg/L).