These Colors Don't Run - Remember 9.11.2001 Equipped To Survive
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Water and Food Group
Water Storage Containers Water Procurement Water Purification
Water Filters Hyperbole Real World Experience
Katadyn General Ecology Recovery Engineering - PUR
Mountain Safety Research SweetWater Relags
The Rest Sea Water Into Fresh Water Rations and Such

Water and Food Group

I cannot possibly over emphasize THE CRITICAL IMPORTANCE OF CARRYING ADEQUATE SUPPLIES OF WATER. It may weigh a lot (2.08 lbs/quart plus container), but nothing is more vital for your body. Generally speaking, you can survive for weeks without food, but only days, or less in some circumstances, without water. Water is essential for your body and mind to function properly. You need both working as well as possible. The adverse effects of dehydration on your mental faculties, even mild dehydration, as little as 5% to 10%, are insidious and extremely dangerous in a survival situation.

The more arid the region you live in, travel through or fly over, the more water you should carry. The only reliable source of water in the desert, particularly in the summer months, is what you bring along! During the summer months in my desert area I carry a minimum of an extra gallon of water per person. Two extra gallons wouldn't be unreasonable. Minimum recommended for most climates is one quart per person and you should carry more, if possible. Always carry some water with you. In an emergency, for immediate medical or other uses, you may not have time to procure it, even in areas where it is readily available.

Packaged waterYou can use prepackaged water in 125 ml flexible pouches, "flex-paks," (4.227 fl. oz./ 1/8 qt.) (S.O.S. Food Labs and Mainstay are two of the most commonly available brands, but there are dozens worldwide that package this way), 250 ml "Aqua Blox" aseptic packages identical in concept to the boxes juice and other drinks are packaged in, including a little straw attached to each box, (8.45 fl. oz. / 1/4 qt.) or bottled water off the grocery store shelf in plastic bottles.

One disadvantage to the flex-paks and the Aqua Blox, is they have a tendency to leak when squeezed or crushed, as might occur when tightly packed in a survival kit. This is particularly a problem with the flex-paks. Best to vacuum pack them or place them inside a Zip-Lock style plastic bag. The flex-paks are also very easily punctured, so be careful how you pack and handle them. Finally, once opened, the flex-paks must be consumed or the water stored in another container because they cannot be resealed. One option is to pack the flex-packs inside a large mouth water bottle for protection, which also gives you a suitable water container with little wasted space.

TAqua Bloxhe Aqua Blox have sturdier packaging than even the conventional aseptic boxed liquids and thus stand up to abuse far better than the flex-packs. Their boxed shape makes them much easier to pack in most kits. The included straw makes is far less likely that any precious water will be wasted. While they cannot technically be resealed, we have found that a piece of duct tape does a fair improvised job of resealing the package. For most uses, we prefer the Aqua Blox to the flex-paks, but they do generally cost a bit more.

Both the flex-paks and Aqua Blox are USCG Approved with five year shelf lives.

Alternatively, you can use canteens or similar containers. These can be filled at home. Tap water or purified "bottled" water is generally good for six months to a year's storage if kept away from the light. Or, you can sterilize the water and storage containers like done for home canning, assuming they will hold a vacuum, and it will last for years, just as the prepackaged water will.

An easier way to sanitize the containers is to use an Iodophor solution. Iodophor solutions are iodine based sanitizers commonly used in the food and beverage industry and a typical 4 oz. bottle will be more than enough and it is inexpensive. Almost any supplier of home brewing equipment and supplies will have it in stock and will be able to offer tips on proper dilution of the concentrate and contact time, which generally only takes a few minutes.

Water Storage Containers

When selecting water containers, note that wide mouth designs are sometimes easier to fill in the wilderness, though they are also somewhat more prone to water loss while drinking. The wide mouth designs will also mate directly to many water filters. Square or rectangular designs are much more space efficient in the survival kit than conventional canteen styles.

If you use the pre-packaged flex-paks or Aqua Blox, it is still a good idea to also include a canteen or similar water storage container or a water bag or two which can serve for storage of procured water.

Water storage bags come in a variety of styles. Zipper lock style plastic bags from the grocery store are a poor choice. They are not necessarily 100% watertight, are thin and relatively easily punctured and, most worrisome, can easily come open at the most inopportune moment, losing vital water.

Commercially available water storage bags can be divided into two types, thin bladders and heavier duty bladders. The thin bladder style are comprised of a very thin lightweight plastic inner bladder with an integral spout at the bottom which is fitted into a nylon cloth carrying bag, usually open at the top with two handles. The bag serves as the primary protection for the thin bladder. Despite the protective bag, it can easily be punctured by needle like objects.

Another product in this style is the military style 5 qt. bladder canteen. It is made of thicker and tougher material and has a traditional canteen style cap on the top which is much easier to work with. It doesn't pack down as small as the others however.

Flexible water bags and bottles of heavier duty flexible plastic material are now available in a variety of styles from a number of manufacturers. Some come with wide mouths and most have the ability to include a water tube so you can drink directly from the bladder or bottle held in a backpack or similar container. The flexible bottles also usually have available a self-sealing spout style cap. The first on the market with this sort of product was FastTrak Systems' with their well regarded "CamelBak Hydration Systems." The first to market the flexible bottles was Cascade Designs with their excellent "Platypus" brand. We have used both with good results.

They are still subject to damage due to sharp objects, but the material is inherently more puncture resistant than the thinner bladders. They are also more easily repaired and repair kits are available, which should be included if you are going to rely on these water storage products..

The MSR "Dromedary" bag is a very heavy duty rubberized woven material which is more resistant to puncture. It incorporates a standard wide mouth bottle filler cap. These are an excellent water storage bag, but they are expensive and relatively bulky and heavy compared to the others.

Every kit should include a water bag or some other water container to hold water, either for treatment or for storage. For the smallest personal kits, condoms (dry, not lubricated) will work, though they are not easy to use. You must be very careful handling them and setting them down when filled is almost guaranteed to cause a leak as they are easily punctured when filled with water. A sock can be used to protect them, if need be. Be sure to rinse the powdered release compound from the condom before using. Zip Lock bags or plain plastic bags will also work, but they won't pack down quite so small. Obviously, purpose made water bags, canteens or water bottles are the best choice, if there is room.

For more information, read an archived in-depth discussion from The Survival Forum on the subject of Condoms and Alternative Water Containers for Mini-Kits

Water Procurement

Survival manuals present many methods of procuring water in the wilderness. By and large, most of them will work for you, but with varying degrees of success. Most methods require little in the way of special equipment. A shovel or trowel to dig a seep hole is usually the biggest help. A handy technique for procuring water from small rock seeps is use of a plastic drinking straw or a short length of small diameter surgical rubber tubing. Both are light and easily packed.

Solar stills, a traditional inclusion in almost all survival manuals and some commercial survival kits, are marginally effective at best. The idea is to dig a hole a few feet in diameter and a foot or two deep, cover it with *clear* plastic and collect the water that condenses on the plastic and drips into a container at the bottom of the hole. A rubber tube (typically surgical rubber tubing) allows you to suck the water out without disturbing the solar still. Production is increased by urinating and placing vegetation in the hole.

They really only work well if the soil is already moist enough that other procurement methods would probably work better. Water lost digging (sweat and respiration) and preparing one generally cannot be recouped by its output. In all but the softest or sandy soil, it is all but impossible to dig a decent sized hole. We're talking last resort here. If you must make one, try to do the work in the cool evening or at night. On the other hand, they aren't a complete waste. Both the plastic sheeting and rubber tubing have other uses.

A better method, in my opinion, is use of "transpiration bags." Quick and easy, they work anywhere there is green "leafed" vegetation (bushes, scrub, trees). Bright sun improves their output significantly. Wrapping clear or semi-clear (opaque won't work) plastic or plastic bags around green foliage and tying it tight traps the moisture given up naturally by transpiration and increases output because of the trapped solar heat. A rock in the bag or tying a corner down makes a low point for the water to collect. You should carry three or four bags per person. These can be light weight semi-transparent garbage bags, but they do tend to tear easily on rough vegetation, so heavier weight bags tend to perform better.

The best transpiration bags I found were offered by Global Survival, packed three to a package with instructions. They were made of some special plastic, so I was told, and were much more difficult to puncture than regular trash bags, as well as being larger. Unfortunately, they are no longer available.

Obviously, these bags have multiple uses, so they are not a bad idea to have in the kit in any case. You can even use them as a solar still of sorts by placing mashed cactus and the like in the sealed bag. Transpiration bags are a good choice for desert use, but again, they should only serve as a backup to your own water supplies.

Water Purification

You should always carry the means to purify water you may find or procure. With the exception of rain water, dew, melted *clean* snow, water produced by distillation (solar still or transpiration bags) or the like, you should avoid drinking water from any natural source without treatment, unless there is no other choice. Having said that, however, don't be so afraid of the water that you avoid drinking because you have no way whatsoever to purify it. Dehydration is guaranteed to cause you serious problems, while the risk of contracting something from untreated water is much less certain. Much better to risk a bout of Giardiasis, for example, which can take a week or more to develop, by which time you can hope to be rescued, than to perish from dehydration, a particularly unpleasant and agonizing way to die.


Most commercial kits include chemical water treatments, as opposed to mechanical water filters. Chlorine formulations, generally in the form of "Halazone" tablets, was a popular personal water disinfectant in the past, but has lost favor in North America for the most part in recent decades, though other chlorine treatments remain popular outside the U.S. and for disinfecting large quantities of water for communities and large camps in disaster areas. The EPA, FEMA and Red Cross all suggest using household chlorine bleach for emergency treatment of water and most major cities rely upon chlorine it for their potable water treatment.

From the available literature, chlorine appears to be more sensitive to the issue of organic contamination and its ability to hide the nasty bugs from the treatment process. It also has the down side of outgassing rapidly from open containers and appears to be more adversely affected by colder water temperatures. When chlorine is used, it is important to eliminate organic material as much as possible, either by straining, filtering or some other means, and to ensure the water container is kept closed for the duration of the treatment.

One chlorine based personal water treatment that has been accepted in the U.S. and by the U.S. military is Chlor-Floc. Produced in South Africa by Control Chemicals, it is distributed in the U.S. by HQ Company. Each "600 milligram tablet provides 1.4% available chlorine (from sodium dichloro-s-triazinetrione) and enough flocculating agent for the clarification and disinfection of 1 liter (1.1 quarts) of water from polluted sources at temperatures of 77 degrees farenheit (25 degrees C). At 41 degrees F (5 degrees C) two 600 milligram tablets will provide 2.8% available chlorine for the same purpose" to quote from the supplied instructions.

These tablets are fairly large and are strip packed 2 x 2 in strips of 10 (2.375 x 6 x 0.187 inches), so they are not particularly compact for use in a personal survival kit. The flocculation action helps deal with the issue of organics in the water.

The most popular of the chlorine products overseas are all similar: Galpharm International's Aquaclear, DermaTech Laboratory's Puritabs and Medentech Ltd.'s Aquatabs. These personal size tablets of sodium dchloroisocyanurate are small and a 2 x 2 strip of ten is very compact (1.562 x 4.15 x .093 inches for the Aquatabs, for example), perfect for pocket size survival kits. In fact, BCB Survival, Penrith Survival Equipment and Bob Cooper all use these products in their pocket size survival kits (see Pocket Size Survival Kit Reviews). Reports from those who have used these products have been positive.

These chlorine tablets typically have a five year expiration.


We are often asked about the use of household bleach for water disinfection. It isn't our recommended treatment, but having said that, for emergencies, 6 "drops" or 1/4 teaspoon of bleach (5 1/4% sodium hypochlorite) per gallon of water is the generally recommended dosage. The chlorine should be given at least 30 minutes to react, at normal room temperatures, double that or more if colder. If the water is "dirty," a double dose should be used and the water should be agitated at regular intervals (dirty water can shield bacteria from chlorine, so more chlorine and/or more contact time is needed).


Iodine based treatments remain the most popular disinfection method in the U.S. these days.

Note: Neither iodine nor chlorine are effective against Cryptosporidium. This protozoa is still fairly rare, but if you are concerned about it, then you need to either boil your water, filter it with an effective water filter, or use Katadyn's Micropur MP1 or the MSR MIOX device (see below).

The most practical commercial iodine products are either "Polar Pure" iodine crystals/saturated iodine-water solution by Polar Equipment or "Potable Aqua" tablets (Globuline-Tetraglycine Hydroperiodide) by WPC Brands (FKA Wisconsin Pharmacal. The former is a much better choice if minimum size isn't a criteria, the latter is what is most commonly found in commercial kits. It's smaller and less expensive, but has its disadvantages.

A bottle of Polar Pure will be good for 1,000 to 2,000 qts of water, depending upon clarity of the water. The 50 tablet bottle of Potable Aqua will only disinfect 25-50 quarts of water, depending upon how clear it is. Cloudy water requires two tablets per quart and they now recommend two tablets to ensure killing off Giardia cysts as well, so keep that in mind when deciding how much you should carry. While it is the smaller and cheaper package of the two products, by a significant margin, in the long run the Polar Pure is a much better value. The Potable Aqua tablets have a useful life of about 5-6 years and once the bottle is opened, should be used within 6-12 months because the tablets lose potency after prolonged exposure to fresh air. The iodine crystals in Polar Pure will last indefinitely.

Potable Aqua is now available packaged with a same size bottle of "P.A. Plus" tablets which are used after the water has been treated to eliminate the iodine and iodine taste. They work, but I can't say the iodine tastes all that bad to me. If it bothers you, the additional cost and weight is pretty insignificant. For those using iodine crystals, such as Polar Pure, you can always buy a small amount of sodium thiosulfate at your local chemical supply house and put it into a small waterproof container. A pinch or so per quart will have the same effect. Easier perhaps, Ascorbic Acid (Vitamin C) is also effective for eliminating the iodine taste, but some tablets can take a while to dissolve.

For use in small personal size kits, you may need to re-package the Potable Aqua tablets to fit inside the selected container (such as a tobacco tin, hollow handle survival knife, etc.). However, Iodine is extremely corrosive to almost all metals and also affects almost all common plastics, so neither a plastic bag or plastic vial will work. After years of searching we finally found a solution that's easy, effective, and affordable!

Katadyn Micropur MP1Katadyn in 2003 introduced a new tablet water purification product, the "Micropur  MP1" ($14), which uses chlorine dioxide to eliminate all the nasties. Unlike iodine or other available chlorine products, it will reliably kill Cryptosporidium cysts (actually, chlorine dioxide doesn't contain chlorine, but that's a distinction that would require more technical details than we need to get into here).  They claim this is the only chemical water disinfection product registered with the EPA as a "purifier."  Chlorine dioxide leaves virtually no taste when used according to instructions and does not discolor the water.

NOTE: The other chlorine dioxide product on the market, the two-part liquid "Aquamira" ("Pristine" in Canada) by McNett, is not EPA registered. Knowledgable sources tell us its concentration level when used according to directions is not enough to do the job under all conditions. In response to our queries, McNett note that they "do not yet make specific purification claims for Aquamira in the USA," which would come as a surprise if you read their materials, but that's also a subject for another day. In any case, they have declined to answer pointed questions about their product and their claims, to provide requested results of any testing or to provide requested specifics or documentation about their claims to be "approved as a drinking water purifier in other countries."

The tablets are packaged in strips of 10 tablets (2 x 5), three strips per package, enough to treat 30 quarts/liters.  Each strip is about 6 x 2.625 x 0.125 inches. It has a three-year storage life, shorter than other treatment options.

The EPA has also required that the instructions allow four hours for treatment.  We inquired about this, since it seems awfully long for such a treatment in most cases, based on our research into chlorine dioxide water treatment. Katadyn responded that their test results verified full virus and bacteria removal (in room temperature and in cold water) in 15 minutes and elimination of cryptosporidium and giardia in 30 minutes at room temperature.  He explained that, it does take four hours for full crypto kill in very cold, very dirty water.

Katadyn MP1 Treatment Time ChartThus, it appears to us that the EPA required the simplistic four-hour treatment regime instructions since they figure we are incapable of determining whether water is cold or dirty.  Excuse me while I rant a bit.  It is always nice to know your government considers you an incompetent dolt incapable of understanding some simple instructions and seeks to protect you from yourself, even when it penalizes the vast majority.  It would be simple enough to provide some variable specificity of treatment depending upon water temperature or turbidity.  Polar Pure manages to do exactly that for water temperature with a little thermometer to measure water temps. It is also worth noting that were the EPA to require iodine treatments to meet the same standards, they were approved many years ago to lesser standards, that the instructions for same would also require an extended treatment regime.

Why do I give a hoot?  Because some people are going to read those instructions, decide four hours is too long, and then either use something less effective or go without, or they'll drink it sooner and then worry, possibly with unnecessary adverse psychological effects. That's human nature. Ignoring human nature when developing methodology is rarely a good idea. Give us the facts and let the majority of us capable of doing so use products intelligently. Eventually, the EPA allowed Katadyn to provide the chart pictured above to be placed on the packaging, so at least someone who takes the time can see the actual test results.

Based on our research into the matter and review of the Katadyn test data, our opinion is that we'd be comfortable with 30 minutes in all but the coldest and dirtiest water. Of course, water with high visible contamination concentrations should be filtered first in any case, even if just to remove the largest contaminants with some cloth or a coffee filter. 

We also inquired about the safety of using the tablet at higher concentrations, in other words, in less than a liter/quart of water, as might be the situation with an improvised water container in a survival situation.  We were told that this could be acceptable for short term use. A higher concentration (less water) may result in unpleasant taste or odor.  If someone has an adverse reaction to chlorine dioxide in general (which is a rare condition), this risk would increase (similar to the case with those having adverse iodine reactions).  However, in an emergency situation, no negative health issues would be expected.

Katdyn's MP1 has become my preferred method of compact chemical treatment and is what I now recommend. As I go through my personal kits to replace dated items, I am replacing the iodine treatments with MP1.

MSR MIOX Purifier

MSR MIOX Purifier deviceIn 2003 MSR introduced the MIOX purifier. Developed originally by MIOX Corp. of Albuquerque, New Mexico, with a grant from DARPA (Defense Advanced Research Projects Agency, the U.S. military's primary advanced research and development organization), the aim was to produce a compact portable version of the large water purification systems MIOX produces for the military and municipal markets. The process uses electricity to covert a simple brine solution into a concentrated unidentified "mixed-oxidant solution" that is added to water supply, killing off all the bad bugs. The MIOX Purifier is EPA registered, meaning it's passed the gold standard in water purification. Unlike iodine or conventional chlorine treatments, it kills cryprosporidium. The only other field treatment meeting this standard is Katadyn's Micropur MP-1 tablets (above).

Typical use requires a 30-minute treatment regime for giardia, twice as long as the MP1 tabs, but to kill crypto the EPA registration requires 4 hours, same as the MP1. As with the MP1 tablets, we feel that is really ultraconservative and worst case with very dirty and cold water. MSR claims there is no "unpalatable" taste; field reports suggest there is a detectable scent and noticeable taste difference compared to pure water.

To use the MIOX, you first load a small amount of salt into the device. This could be in any form; pellet, rock or just plain old inexpensive table salt. With the salt in place, it is ready whenever you are. One charge of salt will treat approximately 50 liters. When ready to disinfect some water, a very small amount of water, less than a thimbleful, is then added. There is an adjustment that allows you to set the amount of water to be treated, from 1/2 to 4 liters. This is simply a function of time, longer makes a more concetrated treatment solution. For larger quantities you would just produce multiple treatment doses. With the water added and the dose set, you activate the device and you can watch the solution bubble as the electrolysis occurs, converting the salt solution to the "mixed-oxidant solution." Once done, which takes just a minute or so, you poor the dose into the water and let it sit for the requisite time. That's it. No pumping or cleaning required. Place the cap on the MIOX and put it back until needed again.

Obviously, like any chemical water purifier, this only treats the water; it does nothing to remove debris or chemical contaminants.

The MIOX comes with a set of strips that you can use to test the water. After you pour the mixed oxidant solution in your water the chlorine that is part of the "mixed oxidant solution" reacts with what's in the water (microorganisms, silt, algae, etc.) and gets "used up." After 30 minutes, you take one of the strips and swish it around in your water for 15 seconds, take it out, and measure it against a color chart on the side of the canister. (This is similar to the strips used to test pool water.) The strips measure free chlorine in the water. MSR claims that if you have a 4 ppm of free chlorine, than you can be assured you've gotten the kill rates you need to make the water safe.

The unit is 7 inches long and an inch in diameter, weighing in at 3.5 ounces. A pair of 3-volt lithium 123-cell batteries powers it. Battery life is given in terms of gallons of water that can be purified, 200 gallons in this case. It comes with 1 ounce of salt to treat approximately 200 liters of water, 2 CR123 batteries, 50 test strips, instruction booklet, quick reference card and a storage bag. Suggested retail price is $125. That sounds expensive until you do the math. For an occasional user, it may not make much sense, but for a regular user who must purify fairly large volumes of water, whether at one time or over time, it could be cost effective. If you consider the MP1 tablets to be equivalent in efficacy, at an approximate retail cost of $0.45 per liter/quart, 200 gallons would cost $360 to treat, nearly triple the cost. The salt to feed the MIOX is virtually free. Unlike the MP1 tablets, there's no expiration date, though the batteries have a 10-year shelf life. This may also be an ideal solution for disaster use where water may well be available, but its purity is questionable.

MSR promised a unit to evaluate, but to date we have not recieved it.

You do not need to rely on chemical means alone to safely purify water. However, every kit should have a chemical treatment as back-up or adjutant to a water filter, if that is your choice for water purification. For small personal size kits and where size and weight are a concern, chemicals are the only practical solution. When using chemical treatments, you must give the chemicals time to work. Read the instructions and follow them, but consider the times recommended as the minimum required. It is best to allow double the recommended times, if at all possible. Some studies have suggested that it takes longer to kill some of the most hardy cysts, so it pays to be conservative.

Water Filters

Water filters offer the quickest method to ensure pure water. They have their drawbacks, size and weight and maintenance, but if you have room, they offer a lot of advantages, chief among them, speed. Chemicals take time while filters produce copious amounts of clean water almost instantly. That's another advantage, it is clean. Chemicals will, generally, kill all the nasty bugs, but they won't clean up the water. If you are careful how you use filters, they will perform well, but care must be taken to keep them operating properly.

All water filters aren't created equal, but most full size filters will do what they are designed to do, clean the water of dangerous microscopic critters. Recently a lot of smaller filters and mini-filters have come on the market. While many of these work fine, the capacity constraints or basic design of some tend to make them a poor choice for a survival kit.

Water filters can be divided into a few basic categories. First there are those which have a cleanable filter element. These can be subdivided into filters with cleanable semi-permanent ceramic filter elements and those with replaceable disposable elements which can only be cleaned a few times before they need replacement. The ability to clean a filter can be important because it allows you to continue to use the filter after it clogs. In some conditions filters can become clogged pretty easily, despite the user's best efforts to avoid this problem.

The major disadvantage of most of the cleanable designs, as well as the replaceable ones to a lesser extent, is that extreme care must be taken not to become contaminated while cleaning the filter or all that effort to filter the water will be for naught. There is also always the possibility that an internal seal will be damaged in the process of removing and replacing the filter, letting the contaminated water through. The alternatives are designs that use a self-contained disposable filter. Use until clogged, then toss and replace with a new one, no cleaning at all. The obvious disadvantage here is that if it clogs, the only way to continue using it is to have a spare on hand.

Some filters work by gravity, but we will stick with those that use a pump to force water through the filter element. The gravity systems, while effective, can take too long in some situations and aren't as versatile as the pumps, which can suck water from even small sources.

Filters, by themselves, will generally get all of the larger water borne bad guys, micro-organisms, cysts, most bacteria and the like (Giardia, Cryptoporidia, E.Coli, etc.), but must rely on other methods to kill viruses which are too small (.004 - .1 microns) to filter out. Some filters have a form of iodine built into the filter matrix and it is claimed this kills these small pests on contact. Some filters rely on this for control of some smaller bacteria as well. Note that, by and large, bacteria and viruses are attracted to larger particles in the water and cling to these. Removing the larger particles removes the smaller stuff attached to them. This is probably the reason why even those filters which don't filter down as small as some of the finest filtering designs, still seem to be effective.

For those without the built in iodine feature, a two part treatment using iodine to treat the water before or after filtering must be used to assure catching viruses, and in the case of at least a couple filters, small bacteria as well. From the standpoint of reliability, this is probably the surest method because there is no doubt about the treatment being effective, assuming you follow the directions. The disadvantage is that this requires time, negating one of the major advantages of using a filter in the first place. The good news is that waterborne viruses are not much of a worry in North America, though they are not unknown. However, they are a potentially very serious problem elsewhere in the world. In general, few people worry about virus treatment in North America.

A word about filter ratings. These are presented in microns. It is supposed to represent the size of the smallest organism that can be filtered out. If it were only that simple. Bacteria are the real concern here, the other organisms are considerably larger than the typical ratings of these filters, so even the worst will get these bugs. Most bacteria are larger than 0.5 microns in diameter, but some are as small as 0.2, though the ones most likely to cause problems tend towards the larger size.

However there's microns and then there's MICRONS. These ratings are published by the manufacturers variously as "nominal," "absolute" and "average" or often, with no explanation. "Nominal" is the confusing one. To keep it simple, consider that this refers to the size of the largest pore in the filtering medium. However, organisms larger than this size will make it through the filter because they are not hard or rigid like ball bearings or needles, but rather can, and do, deform like gelatin or a sponge to get through. This leads to the "absolute" rating which means exactly what it says, it is absolutely the biggest critter that can pass through, period. This is the most accurate type of rating because there is no ambiguity. "Average" means that some organisms smaller than that won't pass, but some larger than that will and you have no idea what the limits are. Bear in mind that this is only part of the story since some filters utilize other methods to interdict and destroy smaller pathogens.


The various filter manufacturers are a very competitive lot. Their literature is filled with laboratory test results all ostensibly proving their product is the best. It helps to read the fine print of the test results. There is no national standard for testing these devices, though the EPA does provide guidelines. Each includes a long list of various expeditions which have selected and relied upon their filter, usually provided free of charge and sometimes even including sponsorship money, and copies of many testimonials. Their brochures generally suggest all others perform unsatisfactorily, in some manner or other. To say the presentations are somewhat biased would be an understatement, but what else is new? The points made often have some validity, but they are also often picking nits.

Many manufacturers use scare tactics to hammer home the need for their filter vs. others. In fact the whole concept of filtering water is based, in part, on efforts by these companies to instill fear about the safety of the water and the need to get every last bad sounding organism out of it. Not that there isn't a lot of validity to this, but they often go overboard, just a bit, to their advantage.

Real World Experience

My personal experience, and that of the many experts in wilderness travel that I've talked to, is that all the major brands of filters, as reviewed here, get the job done in the field as far as keeping the user healthy. No one I or these experts know who has used any of the better quality filters, as reviewed here, has gotten ill from waterborne contaminants when they are used properly. All the designs have advantages and disadvantages, but most seem to work adequately. There are some, though, which seem to be easier to use and maintain than others. There are only a few totally unacceptable ones in the lot. Beyond that, you must decide what design appeals to you, feature wise, and which fits your requirements and budget.

The claimed filtering capacity (amount of water that can be purified) of these filters should be viewed with considerable skepticism and used only as a guide for rough comparison purposes. A lot like the EPA miles per gallon ratings for cars, somewhat useful to compare, but not likely achievable in the real world. If anything, the manufacturers claimed filtering capacities are further off than the EPA estimates. In the field, capacity is generally quite a bit less, especially if you are not, or cannot be, selective about where and how you obtain the raw water supply. A conservative, but not unrealistic approach would be to figure you will only get a third to half what they claim, at best, and plan from that figure. Note also that the filtering capacity, except for the disposables, doesn't relate to how quickly the filter will clog, just the total amount of water that might be expected to be filtered before it can be of no further use or effectiveness, even if cleaning is attempted.

Use of a prefilter will extend the life of the primary filter a great deal. It is always a good idea to use a prefilter, but especially so with designs that have disposable or replaceable filters. The pre-filter is placed in the inlet line between the pickup and the pump and will stop all the larger crud that gets by the pick-up screen before it clogs the fine filter, or harms the pump, for that matter. This will save you a lot of grief. Once the prefilter clogs, it can be easily backwashed to clear it for continued use. The best I've used is by General Ecology, the "First Need Prefilter" ($8). Note that a prefilter is not the foam, perforated steel or mesh pickup filter included with most filters. This only keeps out the very largest particles and dirt. Some people use a disposible coffee filter as a re-filter, with reportedly good results. Use once and throw away.


The best known water filter is probably the Katadyn "Pocket Filter," imported from Switzerland. The ergonomics of the original Pocket Filter suffer in comparison to more modern designs, but you cannot argue with its success over decades of use throughout the world. When it comes to filtering water, the bottom line is, it works. The tough aluminum housing holds a ceramic filter which can be cleaned as needed. Each time it is cleaned, with the included cleaning brush, a small amount of ceramic material is removed, leaving a completely fresh filter surface. Even so, it is estimated that the filter will last through 15,000 or more liters. The filter is rated at 0.2 microns average. Its biggest drawback is the cost, about $250. Not so bad if you are planning on using it regularly, but steep for just sitting in a survival kit. Another liability, from our perspective, is weight. It's the heaviest filter at 23 oz.

A very annoying design "feature" is the lack of an output hose. All that is provided is a very stubby spout with which you must direct the filtered water stream into the container. This is a lot more difficult than it sounds. It can really be a pain in the you know what. Katadyn says they don't include an outlet hose because it can be a source of contamination. Perhaps, but no one else seems to have any problem with it. Some have found you can attach, just barely, a length of surgical tubing. This is easier if you take a small fine metal file and round off the edges of the square shaped spout. If you don't use an outlet hose, be sure you have a container with a wide opening to make it easier to get the stream of clean water into the container.

A final drawback is that the ceramic filter is also somewhat fragile, being particularly susceptible to breakage if dropped when out of the housing to be cleaned, a potential liability. For virus protection you must use a chemical treatment.

The Katadyn "Mini Filter" is less expensive than its bigger sibling, but still costs a whopping $150. For this you get an 8 oz. ceramic filter with much the same advantages and drawbacks as the Pocket Filter, including the lack of an output hose. It only pumps about 1/2 the rate of the larger filter. The plastic housing incorporates a built in diameter gauge (to check if the filter is worn down too far) and cleaning "brush," which is really a device with a small curved surface incorporating some very rough sandpaper like material. The inlet hose stores in the bottom of the filter housing. This filter is a bit awkward to pump and tends to clog much quicker than the Pocket Filter, due, no doubt, to the much smaller filter. If you like the Pocket Filter but want something lighter, this may be just the ticket, albeit an expensive one.

General Ecology

General Ecology's "First Need" filter has also been around for years. Over the years they've made numerous detail improvements and it has become reliable, reasonably sturdy and virtually foolproof. This year they introduced a gravity feed option, "Matrix Pumping System" (who comes up with these names, anyway?), a very nice option to the pump, when you have the time and appropriate water source. The carry bag converts for use with the gravity system, utilizing plastic bag liners and a special fitting attachment. The pump is now field serviceable, an important improvement as that has been a weak point in the past. Using the First Need can be aggravating for some. It is a bit cumbersome and awkward to use compared to other filters with better ergonomics, but it isn't so bad as to make it unacceptable.

First Need claims the smallest "absolute" filtering capability, 0.4 microns, 0.1 nominal. It also has a charcoal filter which will capture many chemicals, including any iodine you might use to pre-treat the water for viruses.

At the other end of the price spectrum from the Katadyn, it is about $69 for the "Deluxe" version, often deeply discounted. Its disposable filter cartridge ($29) is both its greatest advantage and biggest disadvantage. It cannot be easily cleaned once it is clogged from use. It can be backwashed, but the procedure is something of a pain in the you know what and you must remember to pack a small amount of chlorine bleach and have appropriate containers, a poor solution for survival kit use.

The First Need's rated capacity (300 - 400 liters) is about half that claimed by others, but still adequate for most survival uses, especially since that is sans cleaning. A prefilter is an absolute necessity or it won't be filtering for long. A spare cartridge would be a good idea to have along, a necessity in a kit that might serve a large party, but this also adds more weight and bulk. The new Matrix Pumping System will work with a filter which is otherwise too clogged to use, a nice back-up feature.

There are plenty of advantages to the disposable First Need filter. Since it is self contained, there is much less danger of personal contamination as can easily occur with most of the cleanable and all the other replaceable filters. Since it is a depth filter in a sealed container, the possibility it would be damaged or develop an internal leak is virtually nil. Once it is clogged, you know it has reached its limit. The First Need isn't the lightest (14.4 oz.) and isn't quite as compact or easily packed as some others, a disadvantage if space is a concern. Add a spare cartridge and it is even bulkier and heavier.

I carried a First Need in my Primary Kit for years. I still believe it is a good value for survival use. It's simple and absolutely reliable, two very important attributes for a filter. General Ecology also markets the "First Need Original" which lacks some of the bells and whistles of the Deluxe, the most noteworthy being the pump is not attached to the filter making the awkward ergonomics much worse. It also lacks the gravity bag option, all for a savings of $5. Stick with the Deluxe.

General Ecology's new "Microlite" is a lot smaller than the First Need and quite compact (5 1/2 x 2 3/4 in.), weighs less, only 7 oz., but that's not quite the whole story. The disposable filter has much less capacity, a lower flow rate, and larger rating (0.8 microns absolute, 0.5 nominal). It is also even less expensive, about $39 including one replacement cartridge. You'll need the replacement cartridge, and an additional set or two would be a good idea ($12.95 for a pair), because its rated capacity is only about 50 quarts, one sixth of its bigger brother. The good news is that the replacement cartridges don't weigh much, only 35 grams (1.2 oz) each, so it's not a great burden to carry a supply of them, but you can see how that will negate some of the weight and cost savings.

The Microlite doesn't have an outlet hose. You either screw it onto a wide mouth bottle (make sure you have at least one in the kit) or use a so called "spout" which directs a stream of water to the side which can be caught in a small container like a cup or mug. To use the unit comfortably, it must rest on the ground, or be screwed onto a bottle resting on the ground. Because its absolute rating is only 0.8 microns, not small enough to get all bacteria, it is virtually a requirement to use a chemical pre-treatment, defeating a major advantage of using a filter. A bottle of Potable Aqua is even supplied. The filter will remove the iodine taste since it also filters chemicals with an activated carbon filter like its larger sibling. Regardless, the need to pre-treat for even assured bacteria protection is a serious drawback. The Microlite is a bit disappointing. Both the lack of a proper outlet hose and the need to pre-treat are significant failings. The even smaller General Ecology "Trav-L-Pure" is not appropriate for survival use at all.

Recovery Engineering - PUR

(Update: 08/2003 Katadyn purchased PUR in 2002 and their filters are now sold under the Katadyn name.)

The full size "Guide" ($80) is Katadyn's follow-on PUR's popular mid-szed "Scout" and offers a good combination of ease of use and filtering/purifying capability. It is one of the easiest pumping and pumps about a liter per 35 strokes, more or less, among the tops in volume per stroke. The Scout weighs in at 14 oz. The disposable membrane filter cartridges (0.3 microns nominal) can be cleaned a few times in the field, if necessary, before needing replacement ($45 / $40) and is rated at about 800 gallons. It includes a granular activated carbon core to filter out most organic chemical compounds and the like.

The iodine matrix that was reputed to kill all viruses and which was a hallmark of the PUR line has been discontinued. Viral protection will require chemical treatment.

The Katdayn "Hiker" is their offering in the less expensive ($60) filter sweepstakes. At 11 ounces it doesn't save much weight over the Guide and is not a whole lot smaller. It filters down to 0.3 and doesn't flow as much water as the Guide.

Its replaceable filter element ($25), is rated for 800 qts., and is only somewhat cleanable. By that I mean you can't brush it, rather you must swish it around in water, any water, not necessarily clean water. The obvious problem with this is that you must have a reasonably large water supply, something that isn't guaranteed. This also only removes a small portion of the contaminants as compared with brushing. It too includes a granular activated carbon core. Aside from being a few bucks cheaper, I can't see any significant advantage of the Hiker over the Scout other than that it is a bit more compact.

Mountain Safety Research

The original MSR (Mountain Safety Research) "WaterWorks" filter had its share of problems. Some great design features, but functionally, it was just a bit of a pain in the you know what to maintain in the field with the main filter element being the primary culprit. It clogged very easily or allowed so much through that the secondary membrane filter was clogged. Their latest version integrates a number of improvements, the most important being a ceramic primary filter, remedying the worst problem and creating the current version, the WaterWorks Ceramic. A lever action pump handle makes pumping almost effortless initially and still pretty easy as the filter gets more severely clogged. It is easily the best of all the filters in this respect.

The WaterWorks employs a three stage filter process, with replaceable ceramic (0.3 microns) and carbon block primary filters and an even finer replaceable membrane filter (0.2) after those. MSR's test results indicate little difference in water quality if the membrane filter is removed. If that is true, it provides a certain amount of redundancy that would be quite comforting. The ceramic filter is cleanable with an included "Scotchbrite" pad, abrading the ceramic surface as with the Katadyn. The difference is that the WaterWorks ceramic is a shell and wears out much sooner, though it still lasts quite a long time, significantly longer than all except the Katadyn. You'd still need to pre-treat the water if viruses are a concern for you.

The pump and filter are field serviceable and a maintenance kit is available that includes some spare o-rings, lubricant and foam for the inlet strainer. It's a sophisticated and somewhat complicated piece of equipment. Complexity is often a weakness, yet reports indicate the filter is reliable and when pump problems did occur, they could virtually always be rectified right then and there. That speaks highly for the basic design. You would, however, want to safeguard the disassembly/assembly instructions. I'd treat them with some Map Seal or equivalent to protect them from destruction, if they get wet.

The WaterWorks attaches to a wide mouth bottle or you can use the supplied outlet hose. This filter has received excellent reviews from those who have used it in the field. Its chief drawbacks are that it is not inexpensive ($140), it isn't the most compact filter, among the largest available, and it isn't all that light, weighing in at just over 17 ounces, but that's not quite as bad as one would expect from its size. If these are not problems for you, it is a good choice.


SweetWater's "Guardian" filter is the lightest of the full size filters (11 oz.). It is also the least expensive ($50) and filters to 0.3 microns nominal. The lever style pump is among the easiest to operate initially, but reports indicate that after a few strokes it quickly becomes hard to pump, which was my experience as well. The disposable pleated paper and granular activated carbon cartridge ($20) is cleanable and rated at about 750 liters. It filters from the inside out, so you do not handle the surface with all the loathsome organisms you've been removing from the water, a nice feature which makes this chore much less onerous. There have been reported problems with it quickly clogging. My evaluation unit would only filter about 14 quarts before clogging, in water the other pumps were having few problems with.

For virus protection, SweetWater sells a chlorine-based solution called ViralStop that comes in a small plastic bottle. You add 5 drops of ViralStop to each liter of filtered water, mix for at least 10 seconds, then wait 5 minutes. The cost is $8 per bottle.

The price and performance would seem to make a reasonable compromise, but I wouldn't consider this filter without using their "Silt Stopper" 0.4 micron prefilter to reduce the clogging problem. That changes the price picture and makes it less of a bargain. Its biggest virtue is that it is so light.


The Relags "Travel Filter" is a less expensive ($150) alternative to the Katadyn Pocket Filter, to which it compares favorably. Rated at 0.5 microns absolute, it uses a cleanable ceramic filter ($75), similar to the Katadyn's. It is rated at somewhat the same life, 14,000 to 20,000 quarts. Ever so slightly bulkier than the Katadyn, it weighs in the same, 21 hefty ounces. The body is a high strength "resin." Unlike the Katadyn, an output hose is included. If the Katadyn appeals to you, but its price or lack of an output hose doesn't, this is the solution.

The Rest

Both the Basic Designs "Ceramic Filter Pump" and Timberline "Complete Filter" are poor designs because they require you to place the filter element itself into the water source. That presents all sorts of problems. Forget about these two.

Avoid, also, straw style filters through which you literally suck the water. Though the concept is appealing, especially for weight conscious survival use, they don't filter very well in the first place and clog very quickly and are then useless. In fact, the EPA forced them off the market a while back, but you still see them around, or you may even have one, in which case, you ought to ditch it.

Sea Water Into Fresh Water

"Water, water everywhere, nor any drop to drink" (Samuel Coleridge, The Ancient Mariner, 1798). This refrain has been true for centuries. Never, ever, drink sea water! All that you will accomplish is to hasten your death. The filters described thus far are designed for use with fresh water only. Never use them with salt water. They will not desalinate sea water.

Until fairly recently your options were very limited. Traditional chemical desalinating kits have very limited capacity and are really inadequate, to say nothing about the terrible taste of the water produced. Solar stills are reasonably effective, though slow, but are unreliable because you cannot choose your weather and they need sunshine to work well.

The only practical choice for desalinating sea water is Katadyn's PUR "Survivor" series of hand operated reverse osmosis units (or "MROD" - Manual Reverse Osmosis Desalinator). Developed originally for the military in the late 1980s, these pumps literally remove the salt from sea water, leaving fresh drinking water. Every life raft should be equipped with one of these watermakers. (They are not designed for use on fresh water and their high cost and low output would make that a poor choice in any case.)

PUR 06 watermakerThe smallest unit (Survivor 06), appropriate for small to medium size life raft use, weighs only 2 1/2 lbs. and is designed to fit in the space required by two chemical desalter kits. It has virtually unlimited capacity at the rate of just over a liter per hour. However, it takes considerable effort, a lot of steady pumping at a pretty rapid rate (40 strokes per minute), to turn that salt water to fresh and output is very slow, frustratingly so at times for the effort expended. If you are using it for any length of time, you are guaranteed to have strong arm muscles. But, you will be alive to tell the tale.

A better solution is the "military" version of this model, the Survivor 06-LL. This model is much easier to pump because it has an extension for the pump handle, giving additional leverage and an extension for the pump body with a Velcro strap to secure it to your leg while pumping, so you don't have to use both hands. Together these two additions make a huge difference in ease of use. The down side is that it costs nearly half again more than the standard unit and is very difficult to nearly impossible to obtain these days as they have quit selling them to consumers. Unless a few extra ounces would be a burden, the 06-LL is the best choice, by a large margin. Personally, I wouldn't care to fly over the ocean or put to sea without one in the life raft or ditch kit/grab bag.

There is also a larger model, the "Survivor 34" which will produce nearly 1.5 gallons of fresh water per hour. This is the unit that was used by Bill and Simone Butler during their 66 day marine survival ordeal. This unit is 22 inches long and weighs in at 7 lbs. It is far easier to pump, and obviously puts out lots more water with each stroke, but its size and weight make it best suited to larger capacity rafts where weight is less of an issue and water requirements are greater. On a boat, where it may well be used for normal fresh water production, this is less of a problem.

Rations and Such

While food is generally not nearly as important as water, it can make a survival situation considerably more bearable. You can survive without food for weeks without permanent side effects, though your ability to function and affect the outcome of your survival situation will be impaired. After the first day or two, which can be difficult psychologically and physically as your mind tries to "encourage" you to eat, your body and mind adjust and it is more easily tolerated.

On the other hand, food can be a tremendous asset. Food will help keep you alert and in a much better state of mind to deal with your predicament. In cold weather, survival rations become much more important because your body needs those extra calories to stay warm.

A caution - IF YOU HAVE LITTLE OR NO WATER, DON'T EAT! It takes water for your body to digest and metabolize food. Therefor, generally you don't want to eat unless you have two or more quarts of water per day available. There are exceptions to this rule, for example, a marine survival situation and when the food you have available contains a high percentage of water, such as some fruits.

When selecting food for a survival kit, bear in mind that the ideal survival food is long on complex carbohydrates and fats and short on simple sugars and protein. Complex carbohydrates and fats provide a readily digestible and sustained energy source which will see you through. Hard candy, a common survival kit inclusion, is great for a quick energy burst, but doesn't help in the long run and can actually be counterproductive if you cannot follow it with something more substantial. Foods like jerky (dried meat) and other high protein snacks are too high in protein, useful for building muscle, but not easily used for near or medium term energy requirements. They are also more difficult to digest and require more water to metabolize.

I pack two man-days' survival rations per person. Highly concentrated survival rations provide substantially more nourishment, in the area of 2000 kcal per pound, than the typical granola or chocolate bars some kits contain for the same weight. They are also better balanced nutritionally for survival purposes and designed for easy digestion with minimal water requirements. My current choice of those available are "Mainstay" (by Survivor Industries), "S.O.S. Food Lab" or Mayday brand rations. The Mainstay and Mayday have a texture somewhat similar to a shortcake cookie and a mild flavor. The S.O.S. is more like a heavy bran cookie in texture with a "cookie" sort of taste. Both come in various size packages. The S.O.S. is available in a myriad of packaged configurations to better fit different kit packing requirements.

U.S. Military MREs (Meals Ready to Eat) are an excellent, completely balanced food, if weight and space are not a big concern. It is best to test these beforehand. Some are actually quite good, other at least acceptable, but some are very unappetizing fare to most people. It is worth buying a few different ones first and tasting them to find out which ones you prefer.

Electrolyte replacement drink mix, bullion, coffee, tea, hard candy, etc. are nice to have, but are not absolutely necessary and certainly are no substitute for real rations. Salt, pepper or similar spices can help a lot to improve the taste of many foodstuffs procured from the wild. One person I know includes a mini-bottle of Tabasco Sauce. Anything tastes good with that on it, he tells me.

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