Over the last week or two, I’ve come across a number of articles and videos on-line, discussing the latest, greatest sponsored products for water filtration and/or purification. In far too many of them, I’ve seen zero discussion about HOW and WHY filtration and/or purification systems work, and why they don’t. In order to address some of those issues, before folks go out and start buying suboptimal (for their area and regional environments), I figured I’d go ahead and share a portion of my most recent book, discussing not just a few favorite water filtration options, but also why some of them are less than optimal, depending on your regional requirements. (TLDR: If you live in an urban or heavily industrialized agricultural area, boiling is a TERRIBLE method for water purification. Suck it up and read on to discover why…) Water Sources In assessing the safety of any water source—even in the remotest backcountry regions of North America, let alone in an urban or suburban stream or rivulet—the only safe rule is: “Treat it as tainted.” In my youth, and even in some of my early backpacking adventures as a young soldier and NCO, I regularly drank from creeks without worry about filtration or treatment, if I was sufficiently remote from civilization to feel reasonably safe. Today, between having children, and being more circumspect about my previously cavalier attitude towards my own safety, welfare, and survival, I’m much more responsible. Even when high in the alpine fastnesses of the legally-designated and protected Wilderness, I filter or purify my water. The sad reality is, absent absolute necessity, the days of drinking directly from streams is over unless you’re a complete fool. It can be challenging, standing next to an apparently pristine mountain stream, with a torrent of cold, clear, glacier fed water flowing past, to believe that it is almost certainly polluted, but chances are, it is. The potential danger can arise from any of numerous infectious organisms, but the majority—probably 90% or more, most transmitted by feces—account for most of the potential trouble. If you don’t think that the problem will be even worse, in a grid-down type emergency, with people defecating wherever they feel the urge, while lacking enough sense to properly dispose of their own wastes, remember that previous fact: most transmitted by feces. In much of the US, the most common of these is going to be Giardia. Giardia lamblia is most most often passed from organism to organism in the form of a microscopic oval cyst roughly 10-20 microns in size, although they may be as small as seven microns1. One stool from an infected mammal can produce about 300 million of these cysts, and it only takes about 10 of them to effectively infect you. The cysts are swallowed, most often in water that the feces has polluted, and reach the small intestine. Once they reach the small intestine, they hatch into active, wineskin-shaped trophozoites, then divide and multiply, and soon establish a ravenous colony. Of the tens of millions of Americans now likely infected with giardisis, or “backpacker’s disease,” many are only carriers, remaining apparently perfectly healthy, with no signs or symptoms manifesting, but they can excrete live cysts for weeks, months, or even years, post-infection. Those unlucky who do manifest symptoms though, find it onerous, at best. After an incubation period of one to two weeks, you will suffer diarrhea, cramps, visible bloating and explosive gasiness. Weight loss, both from the direct actions of dehydration and due to loss of appetite, soon follow. Unfortunately, humans are only the initial vector in many places. Other animals that act as both carriers and sufferers include cattle and horses, dogs and cats, rabbits, coyotes, and beavers, hence the other common sobriquet, “beaver fever.” All of these are of course, much less fastidious about the location of their toilets than even the most careless humans, outside of urban ghettos, are. These wildlife carriers make it so that, once a watershed is infected, there’s little chances of ever eradicating Giardia in that area. In addition to biological contaminants like Giardia, Cryptosporidium, various bacteria, and even viruses, there is the risk of other, non-biological contaminants in water that needs to be considered, especially in urban and other well-populated areas. While generally safe from Giardia and Cryptosporidium, mineral springs, especially in the desert, can be toxic. One common culprit in the western US deserts is arsenic. What you do if you suspect an unposted, bitter tasting spring is laced with arsenic I’m not sure. I suppose if you’re in immediate danger of dying from dehydration, you take a drink anyway, and hope for the best. If you’re not in immediate danger of dying, you stand around debating the merits of drinking it, versus being thirsty for awhile, then you shrug your shoulders and walk away2. On the other hand, I’ve known more than a few vile looking springs, both in the West and the Southeastern US, that were regularly utilized by some tougher than boiled boot leather old timer, “with nary a ill effect!” Another common source of toxicity in standing water sources in the Western US is selenium. In trace quantities, selenium is a necessary micronutrient for mammals, thus the presence of selenium salt blocks for livestock. Standing surface water though can contain deadly amounts. The water itself may bear no visible signs, but from my personally limited experience with known deposits of selenium in ponds, there’s a slight garlic smell to it. Allegedly, the presence of the plant called “Princess Plume” is also a good indicator of high levels of selenium. A distinctively visible sign of potential danger is what used to be referred to as “alkali water.” This will be noticeable as a whitish crust around the edges of the water hole, indicating high levels of dissolved salts in the water. If it’s not toxic, it will—at the very least—be extremely laxative in effect, with the same dehydration dangers as giardisis. Again, if you’re dying, it might be worth it to take the risk, but…probably not. Dying is bad enough. Dying with Montezuma’s Revenge would be humiliating. In “civilized” areas, where mining, farming, ranching, or other industry has taken place upstream, heavy metals, nitrates, phosphates, herbicides, and pesticides can all be found, and not all filters will remove chemical compounds from waters. In winter, in some places, snow will be the surest, and often only, source of water. I’ve spent so many years in the northern Rockies that I no longer view snow as some sort of implacable winter foe, but as an old—if temperamental—friend and confidant. For every commonly voiced complaint about snow, in the North country, there are 2-3 corresponding benefits; it just takes experience and exposure and mental adjustment to discover the wonders3. The real hurdle in getting potable water from snow is not the moisture content, but the state change from solid to liquid. Pushing solid water—ice–the last one degree of temperature to a liquid state, requires an extremely expensive 80 calories per gram. This is why putting a water bottle full of snow inside your clothes or sleeping bag to thaw, is a terrible idea. It’s going to suck your body heat away, and drive you straight to hypothermia. Even in the depths of winter, whenever remotely possible, it is important to strive to find open water for use. While snow-covered streams promise unreliable footing, and often requires lowering water containers via a rope or string, it’s still a net saver of both time and fuel. The surest way to reliably get adequate water from snow is to concentrate the water content. Once you’ve eaten for the evening, had water hot/warm drinks you’re going to consume, and cleaned up after yourself, let your fire die down, or turn the stove off, and set a pan of snow on it, with just a swallow or two of water included. Let the residual heat melt the snow—instead of burning the snow with direct heat. In the morning, the refrozen ice melts more quickly, and produces more water than the same pan full of fluffy snow. When you wake, take a couple of healthy swallows of cold water to refresh yourself and get your bodily systems working, ignite the fire or stove, and pour the rest of the water into the ice-filled pot to aid in the melting process, and soon you’ll have another pot of potable water. Water Purification Even the coolest, cleanest looking stream in the most remote corner of the Bob Marshall Wilderness will yield an unhealthy army, poised to bring you to your knees. Fortunately, from the wonders of modern manufacturing comes several potential solutions, almost none of them as effective as promised by the marketing gurus and Internet experts. Lo these many years ago, in the dim recesses of ancient time, in 1996, Backpacker magazine published one of the single most useful articles that much lamented journal4 ever produced. A special report by author Mark Jenkins, it was what still stands as one of the most understandable treatments of water filters and purifiers for the backcountry written. In companion with the 1998 book Purification of Wilderness Waters by David Cooney, you have a graduate level education in the “icky” in wilderness water, and how to remove it. Cooney’s book, has not only detailed explanations of various contaminants, but includes a thorough look at the different chemical treatments and the most common water filters on the market at the time. While twenty five years might seem like a long time ago, when it comes to water filter technology, the explanations Cooney—a chemical engineer by training and profession—provides about why the various filters work or don’t, is useful when comparing to more modern iterations. Most gastrointestinal distress from “polluted” water involves three different types of microorganisms that spend at least a portion of their life cycle inside your digestive tract. Protozoa are simple one-celled beasts that for shelled oocysts, from 4-20 microns in size. Bacteria tend to be about 1/10th that size, from 0.3 micron to 2 micron. Bacteria come in three basic shapes: spherical, identified with the prefix cocci-, rods, known as baccilli, and spirals, recognized by the prefix spirillia-. While many bacteria naturally reside in your gut, including benign strains of E. coli, where they are essential for digestive processes and general good health, in water we need to drink, these tend to indicate contamination by other disease-causing organisms. Viruses are subcellular masses of nucleic acid coated with proteins, ranging in size from 0.02 to 0.1 micron. A disturbingly astounding 97% of 10,000 water samples tested in one study showed positive for one of the three. The tested samples were “from streams all across America, Alaska to Arizona, and we didn’t find one without Giardia.” Despite all this infestation, there is still a significant portion of long-time outdoorsmen—including myself—who have drank freely of wild surface waters without getting sick, more often than not5. One likely reason for this is simple luck. Low concentrations of the organisms may simply be too thin numerically, to successfully colonize the digestive system of a person with a functioning immune system. A second reason is simply that some people have better resistance. The very young, very old, or those with compromised immune systems will suffer more than those in robust, good, physical health. A third is the most common: some of us just end up as carriers. Post-illness, no matter how mild the symptoms, we walk around for months or years with the little buggers in our bellies, but suffer no apparent symptoms. There is also the simple probability rule. Whether protozoans, bacteria, or viruses, the consensus of the experts—and common sense—agrees that the numbers will be much more highly concentrated within the host and their waste products, than when dispersed into the volume of water in even a relatively small alpine lake or southern swamp or bayou. Your chances of contracting Montezuma’s Revenge from a digestive tract infection are much greater from the direct contamination of food, unwashed hands, or shared utensils, than they are from consuming untreated water in the outdoors. Apparently, the freedom of the Apocalypse doesn’t include the freedom to not wash your hands. Another major factor however, is temperature, and it’s one that can be useful. The dormant, shelled oocysts of protozoa are extremely tough little things. In water near freezing, Giardia cysts can survive for close to 90 days. Shigella bacteria can survive indefinitely in ice, and so can viruses, in simple dormant states. Boiling, on the other hand, kills them all, without prejudice. The thermal death point (TDP) is the temperature at which an organism cannot survive longer than five minutes. In his book, Cooney cited a TDP for Giardia of 147F, while other protozoa have TDP ranging from 147-169F. In other words, sustaining a water temperature of at least 170F, for a couple of minutes will inarguably slaughter them all. Unfortunately, while boiling is a standard trope for water purification, it has some potentially severe drawbacks. First, boiling consumes time and fuel, and may be impossible, due to security concerns surrounding using fire or stove in a given place at a given time. If hostile actors are in close proximity, the smell and visual signature of a fire—even of a camp stove—may be prohibitively dangerous. Cooling the water back to a drinkable temperature takes more time. Boiled water also tastes atrocious, unless you dump it back and forth between containers for a few minutes to aerate it, although tea or drink mixes can mask this to an extent. Worst—and most important for those surviving in or near inhabited or densely built-up areas—boiling will not remove non-volatile chemicals and heavy metals that are commonly found in surface water in those areas, such as arsenic. If you’re in a relatively wild, rural area, with little or no agricultural production or old mining sites upstream of your location, boiling may be sufficient, and it’s something I use religiously for water purification in wintertime here, but if you’re in a built-up area, you need to look at other options, except in the most dire straits. Chemical Treatments There are two primary, common chemical treatments for questionable or known polluted water. Chlorine, or bleach is the first. The amount of chlorine is most municipal water supplies is approximately 0.5g per liter. That is not enough of a concentration to kill either Giardia or Cryptosporidium cysts. Even in higher doses, chlorine is not particularly effective. Chlorine also loses most of its effectiveness in cold or heavily alkaline water6. It also doesn’t work well with water that has a high organic content in the form of silt, algae, or dead leaf matter. It does though, react strongly to this organic matter in water, producing carcinogenic chloromines and trihalomethanes. All that having been said, if you’re treating apparently clear, clean water, from a running stream, chlorine may be sufficient7. For this, the recommended dose of liquid chlorine bleach8 is 0.2 milliliters per quart of water, with a 30-minute contact time. That means, after adding the bleach to the water, you need to wait an absolute minimum of 30 minutes for the chlorine to kill the microorganisms. You should not use powdered laundry bleach, or anything with additives of any sort. The traditional chlorine treatment for military and recreational outdoorsmen, were Halazone tablets. It took five tablets to treat one quart of water, and that lost 75 percent of its chlorine within two days after being exposed to air, which of course, happened every time you opened the package to treat water. More modern treatments include the ever popular prepper standby Aqua Mira. It treats up to 115 liters of water using a chlorine dioxide and phosphoric acid combination. These are mixed, seven drops each, and allowed to stand for five minutes, before adding to the water bottle to be treated. It still requires a 20-minute wait for treatment to take effect. If you are treating with bleach, the smell and taste can still be gag-inducing, and there are some concerns with the idea of drinking bleach, even in small quantities. Adding a small amount of absorbic acid9 will help mask the taste, and will react with the hypochlorite, reducing it to colorless, odorless chloride, which is harmless. What chloride won’t do though, is have any effect at all on the microorganisms in the water, so it is essential to wait the full treatment time before adding it. Most drink mixes contain some amount of absorbic acid, and I’ve had good luck in the past just dropping a couple of Vitamin C supplement tablets into the water. Iodine is cheap, lightweight, and has long been favored by both mass market outdoor programs, such as NOLS and Outward Bound, as well as the US military. This extremely broad range of users has brought some significant issues to light, over the decades though. First of all, a rather significant number of people turn out to be rather significantly allergic to iodine. If you’re allergic to shellfish, you may actually be allergic to iodine, and suffer the same ill effects from using iodine as you get from consuming shellfish. This is obviously something you should determine prior to investing a lot of money and time into planning to use iodine for water treatment under survival conditions. Dying of anaphylactic shock would be a bad end to your survival planning. This can be achieved through your doctor’s assistance, or by at-home testing. Buy a case of bottled water and “treat” it with the planned dose of iodine. Drink the treated water and nothing else for a day or two and see how your body responds. If you do have allergic reactions, medical assistance is reasonably close by under the circumstances. For the majority of people who are not apparently allergic to iodine, according to the US military, it is perfectly harmless to use iodine, although some other respectable studies indicate that it builds up in your body over time, to toxic levels, so you should not be using it continuously for weeks or months at a time. A second major issue with iodine is that it doesn’t kill Cryptosporidium. While Cryptosporidium doesn’t get the popular press scare mongering that Giardia does, it has similar ill-effects, and is actually probably the most common waterborne pathogen in the world, including in the United States. While iodine has an even worse—subjective, admittedly—gag inducing flavor than chlorine, absorbic acid will have the same effect on that as chlorine, reducing it to an iodide. The most popular currently available iodine tablets seem to be Potable Aqua. These were what we were being issued, even when I was a young Ranger private. The tablets are only for treating water. If you swallow them, you’re going to get messed up, because they are concentrated to a toxic level. They also must be protected from UV light and moisture in the air, which is why they come in a dark brown bottle. If exposed to air, they’ll lose about 1/3 of their effectiveness within a few days. Don’t try to go all ultralight backpacker by repacking them in a Ziplock bag. Keep them in the original bottle, and make sure it is always recapped tightly. A yellow tinge to the tablets is a sign of deterioration, as is crust building up around the threads of the bottle’s neck, indicating it’s time to replace the unused portion remaining. Iodine can kill some protozoans, such as Giardia. A 1989 test though, published in the American Journal of Public Health, 10 used clear, cold water11 and showed that after 30 minutes, almost every commercially available iodine treatments left behind enough live Giardia cysts to make a person sick, with some taking up to eight hours to finally kill of all the cysts. The same test found that not a single chlorine treatment was able to achieve a 100% kill rate against Giardia. An additional weakness of iodine is that, water with a high tannin content, from leaves and other organic substances in the water, will react with the iodine, transforming it into the useless iodide ions. Since it also still doesn’t kill Cryptosporidium, every commercial iodine water treatment product I’ve ever seen strongly urged the use of a filter after treatment. The popular prepper water treatment plan of using regular pharmacy tincture of iodine may work in water at 68F and above, but it needs to be measured out. Dr. Cooney suggested the small plastic bottle intended for eye drops. Carefully and thoroughly washed out, and clearly labeled IODINE in indelible ink, you can use five drops per quart of water as a starting point. Regardless of which chemical treatment you choose to utilize, there are some universals to consider: turbid water should be settled well to allow sediment and other large pollutants to separate, or should be filtered through something like a tight weave bandanna or a coffee filter prior to treatment. After you add the water treatment, shaking speeds up the process, and it is absolutely critical to loosen the cap slightly and slosh some of the treated water to rinse the lips and threads of the container. For many preppers and outdoorsmen, the small size of the containers and the apparent convenience of just putting a couple tablets of something into the water and forgetting about it make chemical treatment a primary option. Combined with the fact that so many of us were issued iodine treatments in the military—even if they were rarely actually used—this provides a degree of peace of mind about using chemical treatments in lieu of drinking potentially polluted water. Unfortunately, as we’ve seen, these have some serious drawbacks, making them, while potentially feasible under the direst of straits, no more ideal than boiling water for most preppers’ imagined scenarios. That leaves us with option of using filters and/or purifiers. Water Filter Systems Whether labeled as a filter or a purifier, these Rude Goldberg contraptions share the same essential purpose: to clean up your drinking water. Despite this, there are significant, potentially important differences between the two, based on how they work. After having had published standards for water purifiers for decades, around 1998, the US EPA finally published standards guidelines for water filtration systems. Devices that pass the tests and meet these standards will have a product registration number clearly displayed, making it apparently easy to select a functional product. However, it’s important to understand the basics, in order to know what you’re actually getting. A filter works by passing water through the device, but trapping microorganisms and particles. The vital metric in these devices in pore size. Pore size can be stated in two ways: nominal or absolute. A nominal pore size is an average, meaning there are going to be pores both smaller and larger than the stated size. In other words, a nominal 5 micron pore size might actually have enough larger pores to allow Giardia to pass through. An absolute 5-micron filter though, will mean that no pore in the filter device is larger than 5 microns, which will be sufficient to trap and hold Giardia cysts. Many filter makers will claim that their products will meet two of the three standards set by the EPA for purifiers, but no mechanical filter device will offer a small enough pore size to remove viruses, which is the third part of that standard. As defined by the EPA, a water purifier is able to “remove, kill, or inactivate all types of disease-causing microorganisms from the water, including bacteria, viruses, and protozoa cysts.12” It must be verified to remove 99.9% of protozoa, 99.9999% of bacteria, and be able to inactivate 99.99% of viruses, which are simply too small to filter out13. In order to manage this, the typical purifier will combined a physical filter with chemical action: most have some sort of resin-based matrix that releases iodine to inactivate bacteria and viruses. Another common method is to use a bed of activated charcoal or silver-impregnated elements. Silver is utilized to inhibit bacteria growth in the filter itself, although the benefit to the water passing through is open to debate. Activated charcoal works by absorbing chemicals via the process of adsorption, meaning the molecules adhere to the carbon particles. This will remove pesticides, herbicides, chlorine, and iodine, and some studies suggest it will also remove heavy metals from the water. For this reason, activated charcoal is commonly available as part of the filter element, or as an add-on cartridge to the unit. Filters for backpacking are made of various materials. These include ceramic, activated charcoal/carbon, various fibers, and plastic mesh matrices, as well as combinations of these. Due to the small pore size needed to filter out protozoan cysts, the filter can tend to clog up very fast when plastered with algae, silt, or other larger pollutants. For this reason, many filters use metallic or fiber pre-filters to catch the coarser material where it can be more easily cleaned out. For filters that don’t feature these—or if the filter is insufficient for some reason—it is a simple and trusted method to strain water through a piece of fabric, ranging from a simple cotton bandanna or piece of a t-shirt, to using coffee filters. For simple filters, the filter element can typically be cleaned via scrubbing, rinsing, or backwashing with clean water. For those filters that offer activated charcoal purifiers built into the filter though, this component will require somewhat frequent replacement, because the charcoal absorbs the chemicals, bonding with them at the molecular level. If you have a filter that facilitates cleaning, it is essential that you not only know how to clean or replace the element, but that you have the means to do so. The rightly famous Sawyer Mini filters, for example, come packaged with a medium sized syringe that is specifically there for backwashing the filter device with clean water to push out any residual crud that has built up with use. I’ve seen a large number of people though, including some self-professed experts on social media, who simply discard that syringe, or leave it in the package, not recognizing its use. Choosing a Filter/Purifier While the simplicity and weight reductions of boiling and chemical treatments for survival water treatment are appealing on their face, in reality, the drawbacks of these methods really make them next-to-last resorts14 for survivors who know what they’re doing, except under limited circumstances. A filter, purifier, or combination device is far preferable, even if somewhat more inconvenient due to complication and heavier weight and bulk, due to greater reliability. Over the years, I’ve used a variety of different filters and purifiers, but have owned only three varieties, of which I feel qualified to speak with any authority. MSR made a beast of a solid little filter called the Miniworks, back in the 1990s15, which was the first filter I owned and used regularly. I bought it for backpacking, and it quickly found a place in my ruck during military deployments as well. I think I paid around $60 for it back then, and replacement filters were about half that price. While stout, at nearly a pound, it repaid its weight with some distinct advantages compared to other filters available at the time. Like most filters, it had a pump handle, but in the Miniworks, this was a plunger rather than a lever, making it easy to hold and requiring only moderate force to pump. The plunger and O-ring enjoyed a clear plastic housing, so you could see if a problem was developing inside. Inside the black plastic body was a 0.3 micron absolute, ceramic element with an activated charcoal core. The ceramic pad could be cleaned with a simple green scouring pad. I don’t recall the expected published life cycle of the filter, but over the course of a decade, I think I only replaced the filter three times, and two of those were because I’d just returned from deployments where the filter had seen a lot of use in very questionable waters. In neither case was the built-in gauge indicating that the filter was worn beyond use, but I wasn’t sure how much JP-8, diesel, kerosone, and other assorted chemicals the charcoal had absorbed by that point. The second filter I’ve owned is still my major water filter, and I’ve had it for close to a decade as well. That is the Katadyn Vario. In many ways, it is almost identical to the Miniworks. It’s roughly the same size, although it feels lighter than I remember the Miniworks, and the pump handle is a lever rather than the convenient piston. Like the Miniworks, it has a ceramic filter with an activated charcoal element, but the Vario has a sort of fiber filter element as well that cannot be easily cleaned. I suspect the filter element is improved over the Miniworks, given the twenty-five plus years between when I purchased the Miniworks and today, but I do know I end up replacing the filter in the Vario every year. This is not due to a flaw in the Vario, or the filter element, but because I tend to use it throughout elk season in the mountains, and by the end of that, temperatures have dropped enough that I’m concerned the water residing in the filter will have frozen and cracked the element. This is a shortcoming common to all ceramic filter elements. The general consensus on preventing it is to keep the filter inside your jacket during the day, and in your sleeping bag at night. Unfortunately, the Vario is simply too big for me to do this comfortably, so I don’t. Like the MSR filter, the Vario has a spring weight over a plastic capsule with foam inside to act as a pre-filter. It’s simple enough to remove and clean, but it’s also small enough to lose easily, especially in reduced lighting conditions, or under stress in a survival situation. It works well enough in most water, but I’ve had it clog pretty badly in a couple cases where there was a lot of moss or other partially rotten organic material in the water. There is also a small section of foam around the end of the inlet hose that acts as a float, intended to keep the hose inlet off the bottom of a water source. This adjusts easily by sliding, and works reasonably well. The interesting part of the Vario is something it also shared with the Miniworks, although in both cases, I didn’t realize it until after I’d purchased the filters and someone else pointed it out to me. That is, the outlet has a nipple onto which another hose fits, allowing you to filter water into any number of different water containers, but there is also wide flange with threads that will fit a wide-mouth Nalgene bottle, or similar sized containers with the matching thread patterns. I don’t recall the exact flow rate of either filter, but have never felt I had reason to complain about either one16. The third filter I’ve used is one I’ve owned for the better part of a decade, scattered across numerous packs, bags, and load-bearing equipment setups, but have only begun using recently. That is the Sawyer Squeeze. I had some serious doubts about this perennial prepper favorite. While the tiny size is convenient, as is the method of operation—just squeeze the feeder bag—and the fact you can use it to filter water into a container or just drink it directly from the filter, the lack of chemical remediation was concerning when we lived back East, with the amount of industry and industrial agriculture in our area. Sawyer claims that the hollow fiber filter removes Bacteria, protozoa, E. coli, Giardia, vibrio cholorea, Salmonells typhi, and microplastics. For my use in Wilderness areas, with no motorized transport or industry upstream of the alpine streams and lakes I utilize, it is probably amply sufficient. In a rural area with lots of industrial agriculture, and the resulting pesticides and herbicides, I’d be hesitant to rely on it. In urban and suburban areas, with the prevalence of even more hazardous chemicals and heavy metals in the soil and water, I would not rely on it, or recommend it, despite my respect for the company and it’s stated mission, according to the founder and president. In general, ceramic filters are going to be harder to pump water through, and will have lower flow rates, while clogging more quickly. They will also absolutely be damaged/destroyed by freezing. On the other hand, they’re easy to clean and maintain, and as such enjoy a usefully long life, when properly cared for and maintained, in the context of maybe not being able to later procure replacement parts. Fiber filters, like the Sawyer, will have higher flow rates, and higher maintenance costs, since you can’t clean them very well, except by occasional backwashing. While a powerful pump and subsequent high flow rate might seem to be the ultimate goal, it is important to consider that some of the microorganisms you are working to exclude may be squishy enough to slim down to ooze through smaller pores, and pressurization may actually force them through in this manner. In the field, pump slow and steady. While microfilters with an absolute pore size of less than 1 micron have been the rage in backpacking circles for well over two decades now, EPA certified purifiers add protection against viruses which may be a major concern in a grid-down environment. Of course, as we’ve seen, the only reliable way to remove dissolved chemicals in your water is through the use of an activated charcoal element. For this reason, both generally, and specifically in industrialized or heavily populated areas, a filter or purifier with an activated charcoal element is all that can, in good conscience, be recommended. A relatively recent trend is the use of micro, or minifilters that fit into the neck of a bottle or plug into the tube of a water bladder, like the archetypal Camelback. This seems like a phenomenal idea, but it comes with a host of unique problems. Usually these, of which the Sawyer Mini is one version, screws to the top of a basic small mouth soda or water bottle, or slips into the hose section of the bladder, just below the bite valve/mouthpiece. A strong squeeze and more than a little patience, is required to get a mouthful of water. This can be extraordinarily frustrating when you’re thirsty, and can be infuriating when you have to miss a step or three, because you’re fighting with the filter. Since many of the brand specific bladder filters are constructed of clear plastic, they can also let in light that allows algae to grow within the filter itself as well. Despite these, the small size, extreme light weight, and adaptability of the products like the Sawyer Mini can make them extraordinarily attractive. 1A micron is one-millionth of a kilometer. If my math is correct, that is 0.001 millimeter. 2A lack of insects around and in the water is a good clue that it’s not life-supporting water. 3Long time readers will have noticed an increased mention in snow and winter conditions concerns over the last several years. This is entirely due to our return to the Northern Rockies, and the central importance of snow in the outdoors life here. It can snow in any month of the year, and even at relatively low elevations. The important aspect of snow though, is the moisture content. For our Rocky Mountain powder, that is generally less than 10%, whereas for maritime and “lake effect” influenced snow, it will run 50% or more. Glacial ice, on the other hand, has been so compressed that, depending on the presence of trapped air bubbles, can be 95% or more water. 4Seriously. I miss it. I got my first subscription as a gift from my mother, when I was about 11 years old. I maintained that subscription until the magazine stopped producing a paper hard copy. I hate the Internet. 5While I have contracted Giardisis in the past, presumably more than once, I’ve only been symptomatic once, although that once lasted a long time. This was also after several decades of drinking untreated creek water as a youth and young adult. 6Alkaline water is that with a pH above 7.5, and is generally found in lakes or ponds with limestone or dolomite bedrock, and in many—most–desert “sinks” that have no outlet. 7I used chlorine drops for years with no ill effect. On the other hand, the one time I displayed symptoms of Giardia, was after spending a couple weeks in the Utah desert, where my primary water sources were cattle tanks put out and maintained by local ranchers. I treated that water with a pre-filter through a shemagh scarf, and then with chlorine drops. 85% sodium hypochlorite 9Vitamin C 10Ongerth, J.E.; “Backcountry Water Treatment to Prevent Giardisis” 1150F 12US EPA “Guide Standard and Protocol for Testing Microbiological Water Purifiers,” 1987. Test organisms used were Crytposporidium, klebsiella bacteria, and poliovirus and rotovirus.) 13I have heard at least one filter manufacturer claim—with some plausibility—that despite their small size, viruses don’t actually travel unless bonded to something larger, meaning that many filters might actually do a better job of removing viruses than the EPA gives credit for. Whether that claim is something to rely on is up to the reader to decide for themselves and their family. 14The last resort, of course, being drinking untreated water, because of necessity and proximity to death from dehydration. 15The current iteration is called the Miniworks EX, and as far as I can tell, the only major difference is the move from a plunger handle to a lever handle. 16Katadyn’s website claims 1L/minute in “longer life” mode, and 2L/minute in “faster flow” mode. That seems about right. It also claims a water capacity of 2000 liters, “depending on the water quality.” https://www.patreon.com/posts/some-...paign=postshare_creator&utm_content=join_link Continue reading...
