Water Filters for the Backcountry Our water was long gone as we stared glumly at what the folks who organized the Utah Eco-Challenge adventure race defined as a spring: an oil-slicked, mosquito-infested sludge pond containing a few odd tires, tons of cattle excrement, and one dead and bloated rat... yummy. Armed with filters and iodine tablets, we managed to procure one gallon of potable water. Although the lack of purity of this water source was obvious, determining what is safe to drink isn't always so easy. Microvermin such as Giardia and cryptosporidium potentially lurk under the surface of the most crystal-clear, seemingly pure water. To drink directly from any natural water source is to risk a bout of nausea, diarrhea, vomiting or worse. Which is why water filters, which continue to get lighter, smaller, and more convenient to use, are essential to have. With a filter, you just pump and drink. Filtering strains out microscopic contaminants, rendering the water clear and somewhat pure. How pure? That depends on the size of the filter's pores (what manufacturers call pore size efficiency). It's a fairly technical matter, but the upshot is that any filter with a pore size efficiency of two microns or smaller will remove such protozoa as Giardia and cryptosporidium, as well as parasitic eggs and larva, but it takes a pore size efficiency of less than 0.4 microns to remove bacteria. All but one of the filters here take care of bacteria. As for viruses, a concern in Third World countries or places where water may be contaminated by sewage, only one field device I tested that relies exclusively on filtration is claiming 100 percent virus removal. Since zapping viruses requires chemical assistance in most cases, some of the filters here turn to iodine disinfection, either as an integral part of the system or by suggesting the addition of Potable Aqua tablets to the purification mix. Iodine tastes awful and it a possible health risk to some people, so many filters employ a carbon-element (activated charcoal) to remove the iodine when its job is done and to get rid of pesticides, herbicides, heavy metals and chlorine. Be warned though: Once the carbon element has reached its limit for absorbing a particular chemical, the bad stuff can then sneak through undetected. You must replace the filter according to the manufacturer's recommended schedule. One additional caveat: The carbon that removes the iodine may, in fact, be removing additional protection you need to ensure a good "kill" of little microbial nasties. Some studies have shown that the quick pass-through of heavily contaminated water through an iodine-resin impregnated filter may not achieve a 100% neutralization of viruses and that it is only because of the trace amounts of iodine that remain in the filtered water that microbes get completely nuked. What's a person to do? I would recommend that if you are in areas where the risk of pesticides, herbicides or heavy metals in the water source are greater than the risk of encountering sewage and viruses, you opt for the carbon element, otherwise, leave the carbon at home. If you really can't handle the taste of iodine, then add a little Vitamin C (ascorbic acid) to the water 15 to 20 minutes after you filter. A good all-around filter should be compact, lightweight (forget anything over 20 ounces), simple to use, and easy to clean and maintain. For the best protection, you'll want to buy a filter that will remove protozoa and bacteria. A number of value-oriented, pocket-size filters remove only Giardia and cryptosporidium, and that, in my book, is risking your health to save money. Consider the flow rate too: A liter per minute is OK; less, and your lips will pucker waiting for the water. All filters will eventually clog; it's a sign that they've been doing their job. If you force water through a filter that's becoming difficult to pump, you risk injecting a load of microbial nasties into your bottle. Some models can be backwashed, brushed or, as with ceramic cartridges, scrubbed to extend their useful life. Because ceramic can be cleaned with a brush or scrubber, they appear to be more expensive but in reality are far more cost effective for the long haul if you're planning on pumping loads of water. If the filter has a prefilter to screen out the big stuff, use it; it will extend the filter's life dramatically (although I've yet to find any pre-filter that will work on the ultra-fine sediment common in southwestern U.S. rivers. For that, you'll need a bucket to hold the water to allow the sediment to settle before filtering.) Typically, filters have a useful life of up to 100 gallons if they are not ceramic, and hundreds more gallons if they are. The bottom line is that no matter what the manufacturer claims on the package, they are dreaming of best-case scenario water which I have never been able to find from any backwoods water source. Expect to realistically achieve only 75% of what a manufacturer claims, and then only if you are very careful. Any of the filters reviewed here will serve very nicely on a backcountry outing -- providing you always follow the manufacturer's instructions and replacement schedules. Basic Designs Ceramic The Basic Designs Ceramic Filter Pump ($32) weighs seven ounces and is as stripped-down a filter as you'll find. The pump is simple, easy to use, and quite reliable. The ceramic filter effectively removes protozoa, making it ideal and cost-effective for backpacking, but it won't deal with bacteria or viruses. Also, the filter element is too bulbous to work directly from a shallow water source, so you'll have to contaminate a pot or bottle to transfer your unfiltered water. It's a great buy, though, for anyone worried only about Giardia and cryptosporidium. Sweetwater Guardian New last year, the Guardian ($50) weighs a scant 11 ounces, and its fingertip-light pump action is the smoothest of all the filters reviewed here, although following an extensive test in Utah, it also seemed to clog more readily than either the PUR or the MSR. After a year, it's proved to be quite durable, although one tester did experience some lever breakage problems. It'll remove protozoa, bacteria and chemicals (activated carbon is in the filter element); add the Viral Guard cartridge ($25 plus four more ounces) and it'll kill viruses too�making the Guardian a suitable choice for international travel. Sweetwater Walkabout New for 1996 and an attempt by Sweetwater to gain acceptance by those who obsess over ounces and prone to counting pennies, the Walkabout ($35) weighs just eight ounces. The filter removes both protozoa and bacteria and is easily cleaned in the field. Water delivery is a tad slow at just under a liter per minute. Although it is lighter (just) and more compact (barely) than it's cousin the Guardian, I think the Guardian is a much better machine and value since it works in all water conditions and its cartridges last longer. First Need Deluxe The 15-ounce First Need Deluxe ($70) from General Ecology is a time-proven filter that pumps easily enough, delivering pure water at just over one pint per minute -- a bit slow for my tastes. However, it just leapfrogged up in value without the company having to lift a finger. Why? Because tests show it removes viruses through filtration with no iodine assistance, in addition to protozoa and bacteria. Still, there is a remote possibility that if the cartridge gets dropped it can crack without you knowing which lets in all the little nasties. Is that a real problem? Well, General Ecology includes instructions on using a bottle of blue dye to test for cracks, the only way to see if the cartridge is damaged since it's sealed in an opaque blue plastic housing. My advise is, carry an extra cartridge with you anytime you are heading miles away from civilization. Katadyn Mini Filter The Mini-Filter ($140) is a much more compact version of Katadyn's venerable Pocket Filter. This one weighs just eight ounces, ideal for the minimalist backcountry traveler, It effectively removes protozoa and bacteria, though its long-lasting ceramic filter element is small, and therefore requires frequent cleaning. I also found it challenging to put any kind of power behind the pump's small handle, and the filtered water is delivered at a paltry half-liter per minute. Still, for saving space and weight, you just can't beat the sleek, palm-of-the-hand packaging, though you do have to pay dearly for it. A 1996 option, although not available for testing as this went on-line, replaces the ceramic element in the Mini with a carbon element to lower cost ($99) and give an improved flow rate and easier pumping. The carbon is intended for those who limit their outdoor experience to clear mountain streams and is not intended for those who head out on more than two or three weekend trips a year or those who will be filtering seriously contaminated water such as that found in Third World sewers or cow pastures, for that you must use the ceramic. PUR Explorer The PUR Explorer ($130), from Recovery Engineering, offers protection from all the bad guys -- viruses as well as protozoa and bacteria -- by incorporating a virus-killing iodine matrix in the filtration process. An optional Carbon Cartridge ($20) neutralizes the iodine's noxious taste. The pumping action is smooth, and with a quick twist the device switches from filtering mode to self-cleaning mode -- a welcome innovation. It's a tad on the heavy side (20 ounces) and somewhat pricey, but it's easy to use and works very well on iffy water anywhere. MSR Waterworks II Ceramic At 17.5 ounces, it isn't light, but for the same price as the Katadyn Mini Filter ($140) you get great flow rate of just over one liter per minute, a long lasting ceramic cartridge, easy fingertip pumping, and best of all, no more clogging problems attributed to a vapor lock in their earlier and now obsolete model (all the new components will fit in the old unit's housing for a less expensive upgrade). MSR has a philosophy of making all of their products fully field-maintainable, which means you can take this baby completely apart, repair or replace anything that stops working, and put it back together, anywhere, anytime, although it's a fair bet to say that if you aren't mechanically inclined, you're going to get frustrated. The filter, removes protozoa, bacteria and chemicals such as herbicides and pesticides, but not viruses. MSR MiniWorks It seems as if every company is trying to field a price-sensitive filter, and MSR is no exception with their new 1996 introduction, the 14 ounce MiniWorks Filter ($59). By all appearances it's the Waterworks II hit with a shrink ray. What's different is that the Mini eliminates the membrane cartridge and its housing which means it can't offer quite the same workhorse attitude of its brother, the Waterworks II. Although the flow rate isn't ideal, the Mini delivers what is arguably the most functionally compact and easy-to-use ceramic filter on the market without breaking the bank, one liter every 90 seconds, which is fine for weekend warriors who aren't planning to hydrate an army. The filter removes protozoa, bacteria, and chemicals such as herbicides and pesticides, but not viruses. PentaPure Oasis The PentaPure Oasis Portable Purification System, from WTC ($30), offers pure water with a twist: You squeeze and sip instead of pump. Weighing six and a half ounces, the system packages a three-stage filter inside a 21-ounce capacity sport bottle with an angled drinking nozzle ideal for mountain bikers. The filter removes and / or kills protozoa, bacteria, and viruses, so it's also suitable for world travel. It's certainly convenient: You just fill the bottle with untreated natural or tap water, screw on the cap, firmly squeeze, and sip -- don't expect the easy flow of a sport bottle. Like the Basic Designs, the Oasis runs into trouble if the water source is shallow, you'll need a cup for scooping. — Michael Hodgson Michael Hodgson's Editorial Field Camp 36 Norton Ave. San Jose, CA 95126 phone: (408) 993-1531 fax: (408) 993-0254 email: [email protected]