Your #1 source for kayaking and canoeing information.               FREE Newsletter!
my Profile
Paddling Articles In the Same Boat

Returning to the Well

A Second Look at Water Treatment Options
Part 2—The State of the Mart

By Farwell Forrest

August 13, 2002

Need a drink? You're not alone, apparently. Tamia's piece on the perils of drinking "found" water provoked more comment than any other recent column. Last week I addressed concerns voiced by a reader in the "Wait Just a Second!" camp. This week, it's time to hear from the "Yes, But…" division. So here goes.

Kirk writes:

I read your water filtering article and though good you miss a lot by not talking about the newer purifications systems out there…. You mention filters, but purifiers are VERY different from simple filters…. Purifiers must meet EPA regulations to even be advertised as being a purifier and most nowadays exceed EPA regulations. Some of these purifiers are the ones like you mentioned in the later part of your article about an iodine impregnated solution, while others like the SweetWater® purification system use a chlorine-based solution in a little bottle after the water has been filtered, so people with iodine problems can use the latter…. [There are even] newfangled ones that use UV light to purify water….

Most backpackers I know have shifted away from using iodine pills as their primary method to clean water and moved to a purifier…. They simply taste better, are faster to produce clean water and actually remove particulate matter from the water. No offense intended, but I think you are doing your readers a bit of a disservice by not covered this topic in more depth and laying out all the options available to them.

Fair enough, and no offense taken. Tamia's original article wasn't intended as a marketplace survey, but Kirk raises several important points, nonetheless. I won't attempt a definitive examination of all available options—my own experience with portable water-treatment systems is limited to chemical germicides and first-generation microfilters, and I've never felt the need for anything more—but I will take a closer look at the state of the mart. Since I don't have an analytical lab at my disposal, I'll have to rely mostly on manufacturers' claims and whatever documentation is available on-line. Still, I think the exercise will be worthwhile. If nothing else, I'll have an excuse to bring my slide-rule out of retirement. (For those born in the last quarter-century, a slide-rule is a primitive, pre-electronic calculating device. It won't give you ten-place accuracy, but at least it doesn't need batteries—and there's no better tool for solving proportions.)

First, though, let's take a look at EPA certification and its limitations. The test protocol used in evaluating water purifiers is laid out in the "Pesticide Program Guide Standard and Protocol for Microbiological Water Purifiers" (Federal Register, Vol. 51, No. 133, Thursday, May 26, 1987). The EPA does not consider most microfilters to be "purifiers." Microfilters do not, therefore, require registration under the provisions of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). As Kirk notes, however, a filter can become a purifier with the addition of any system intended to deliver a chemical germicide. Such devices must then be registered.

The EPA protocol appears to be well thought out, but it has two apparent deficiencies: (1) the pH (a measure of acidity) of test water samples is permitted to be neutral or even slightly acidic, and (2) viral challenges are limited to strains of poliovirus and simian rotavirus.

Why is this important? To begin with, certain chemical germicides suffer a marked loss of efficacy in alkaline water. (This is true of chlorine-releasing compounds, for example.) A certification protocol which does not ensure that water samples reflect a representative range of pHs—both acid and alkaline—may therefore not adequately test all germicides.

The limitation on viral challenges also poses difficulties. The restrictions are, of course, understandable. Viruses are difficult to culture, and many strains pose obvious risks to investigators. Still, viruses are extraordinarily diverse, and relying on only two viruses as proxies for the entire spectrum of viral pathogens makes the certification process more-or-less conditional. So EPA registration, even though a requirement of law and a valuable indication of a purifier's relative efficacy under test conditions, cannot be taken as an iron-clad guarantee that the same purifier will always perform satisfactorily in the field. The world outside the laboratory is a messy and complicated place, after all.

These cautionary comments aside—as always, "When in doubt, doubt" remains the only certain rule—let's take a look at a representative sample of what the water-treatment marketplace has to offer.


Balancing cost, fussiness, and efficacy, most paddlers will find only one germicide worth considering: iodine. While elemental iodine can be used to disinfect water—the so-called Kahn-Visscher method—tetraglycine hydroperiodide (TGHPI) "emergency drinking water purification tablets" are much more convenient. Potable Aqua® and Coghlan's are two widely-distributed brands.

When used according to package directions, fresh TGHPI tablets will reduce the numbers of bacteria, viruses, and some protozoan pathogens to acceptable levels even in "grossly polluted water." The treatment protocol is simple and easy: just add one tablet to each quart of clear water, shake, and then wait ten minutes before drinking. (Double the dose or contact time if the water is turbid—cloudy—or cold.) Cost is moderately high: around US$0.40 a US gallon, though at least the up-front investment is limited to the price of a bottle of tablets (about US$5.00). The cost can be further reduced by employing a "low-dose" regime of the sort that Tamia and I use, but it must always be remembered that this practice invariably impairs antimicrobial efficacy. Prudent paddlers will follow the label directions exactly.

Cautions are few but important. People with thyroid disease or iodine allergy should not use TGHPI tablets. Moreover, TGHPI probably cannot be relied upon to kill Cryptosporidium parvum, a common protozoan parasite. Individuals whose immune systems aren't up to par should therefore look for another treatment method. TGHPI tablets also lose potency with time. They should be kept in a tightly-capped glass bottle, and any unused tablets should be discarded at the end of the paddling season.

Minor gripes: Iodine-treated water has a distinctive—some would say unpleasant—taste, and it stains plastic water bottles brown. The taste can be removed by subsequent treatment with sodium thiosulfate or citric acid, but this increases cost and fussiness.

Recommendations: TGHPI is hard to fault. It's the plain brown wrapper approach to water treatment—time-tested, reliable (when used according to package directions and with an understanding of its limitations), and easy to use. It's got my vote.

Filters—more properly, microfilters—have also been around a long time. Katadyn®, PUR®, and Sweetwater® are among the most widely-advertised brands. The idea is simple: pump water through a filter whose pores are too small for the bugs to negotiate. Dirty water goes in. Clean water comes out. Voilà! The implementation of this attractive idea, however, is somewhat problematic. With one possible exception (see below), microfilters—most of which have pores in the 0.2µm range—cannot hope to trap the great majority of viruses. If this troubles you, and it probably should, you'll also have to employ a supplementary germicide like iodine.

Moreover, filters aren't cheap. Up-front costs range from US$45 (Sweetwater® WalkAbout™) to the venerable Katadyn® Pocket Filter's US$200. Operating costs—that is, the cost of replacement filter-elements—will add another US$0.20 a gallon or so in most instances, though with an advertised life of 13,000 gallons, the Katadyn® should only cost around US$0.01 per gallon. (By this measure, the expensive Katadyn® turns out to be an economy champ. Just don't drop the ceramic filter-element on a rock. A replacement will set you back US$165!)

Caution! Don't rely on a microfilter alone to make your drinking water safe. They're best used in conjunction with a chemical germicide. Many manufacturers formerly employed iodine-impregnated filter-elements to remove viruses, and some still do. Cascade Designs, however, has now discontinued its SweetWater® ViralGuard cartridge, citing evidence developed in its own lab that its "portable iodine resin bead technology…does not meet the EPA standard for purifiers."

Any minor gripes? Yes. Pumping a gallon of water through a filter will take most people three to six minutes, and if you don't have calluses on your hands in the right places you may get a blister. Filters must also be meticulously maintained, and the filter-element periodically replaced. And not all filters will survive exposure to freezing temperatures.

Recommendations: If protozoan parasites (e.g., Cryptosporidium, Giardia) worry you, and you don't mind a little fuss and bother, a filter is a great investment in peace of mind. Just remember to treat your water with a germicide, as well. This belt-and-suspenders approach is as close to bombproof as any field treatment method can ever hope to be.

And now,


One microfilter stands apart from the pack: General Ecology's First Need® Deluxe Water Purifier, the "only chemical-free portable system independently certified to EPA Guide Standard for Microbiological Purifiers." And General Ecology present the summary data to back up their claim. They're understandably reticent about revealing just how they've accomplished this small miracle, however. The published specifications reveal only that the Deluxe is a microfilter with a nominal pore size of 0.1µm, not enough in itself to trap any but the largest viruses.

At US$85, up-front cost is high, but not as high as the Katadyn® filter. Operating cost is moderately high, too: US$0.30 a gallon (under "average" conditions).

Cautions? Beyond the uncertainties inherent in the limitations of the EPA test protocol that I've already noted, none. Belt-and-suspenders types may still wish to treat "purified" water with a germicide.

Minor gripes? Pumping a gallon of water through the Deluxe will take 2-3 minutes, so you'll have to earn your clean water with the sweat of your brow. (Even this nuisance can be eliminated with the "Gravity Assist Kit," however.) You'll also need to protect the filter cartridge from freezing.

Recommendation: The Deluxe should suit almost any paddler with US$85 to spare, though some of us will still want the added security provided by a chemical germicide.

Have you ever longed to own a light-saber? Well, now you can. Like the First Need® Deluxe, Hydro-Photon's Steri-Pen®, "a small and highly sophisticated battery-powered water purification system," claims to meet the criteria "set forth in the U.S. EPA Guide Standard and Protocol for Testing Microbiological Water Purifiers" without using "toxic chemicals." (All germicides are toxic—to germs, of course, and to people, too, if they consume too much of them. The doses used to treat water pose little threat to most of us, though.) And like First Need's General Ecology, Hydro-Photon have the data to back up their claim. In fact, they go General Ecology one better, putting all their consultants' test reports (and their owner's manual!) on their website as PDF files. Reading these is an eye-opening educational experience. Hydro-Photon are to be commended for going the extra mile.

Just how does the Steri-Pen® work its wonders? By zapping bugs with ultraviolet (UV) light. It employs no germicide and requires no pumping. Just switch it on, stir (the Steri-Pen® actually looks more like a hi-tech swizzle stick than a light-saber), and drink. Couldn't be simpler. Still, the devil's in the details, and the details warrant close attention. Arming yourself to go bug-hunting with a Steri-Pen® won't be cheap: it costs US$199. And the operating expense is also high. If you use alkaline batteries (an 8-pack costs US$6 in northern New York stores), and if you get the maximum claimed battery life (chilly weather reduces battery performance), you'll pay another US$0.60 for each gallon of water that you purify.

But you won't be able to purify water by the gallon. A single "treatment" is limited to a maximum of one US pint. If you need a gallon of water at one time (to fill your water-sack for the day, say), you'll be swirling your swizzle stick for 5-6 minutes. (Up to 8 minutes if the water is cold.) That's not very long, admittedly, but it's still more hands-on time than all but the slowest filters.

OK. Are there any cautions? Yes, but not too many. Don't drop the exposed UV lamp on a rock. It will probably break—and release a little mercury into the environment, too. And don't plan on using the Steri-Pen® in turbid or "discolored" water. You can pre-filter turbid water before treating, of course, but I don't know what you can do with the tannin-stained waters of the Adirondacks and the Canadian Shield.

Minor gripes? You'll need plenty of spare batteries. Bring them. If this doesn't appeal, you'll have to spend more money for rechargeable cells and a solar charger.

Recommendation: The Steri-Pen® is an ingenious device, with excellent documentation. It's perhaps better suited to inn-to-inn tours and short trips than to extended expeditions, however. And unless you can be sure that the waters will always run clear, don't forget to bring a filter, too.

That's it. Thanks to Harlan and Kirk—and to all the other readers who wrote in response to Tamia's original article—for their help in exploring the wonderful world of 21st-century water treatment. It's obvious that we've come a long way from the little brown pills that give water a funny taste. Today there's a method to suit every paddler. It doesn't matter which you use, of course, so long as you use something that works for you. And don't forget to bring a back-up system with you on extended trips. As I'm sure you'll agree, the taiga two-step is a mighty poor paddling companion, and thirst is always a dangerous thing!

Speaking of the infamous two-step: Bears do it, bees do it, even educated fleas do it. So do paddlers. Want to know more? Then watch for When you gotta go…, the next in Farwell's series of gutsy, in-depth reports on fundamental topics in back-country health and hygiene. It's coming to a computer screen near you soon.

Copyright 2002 by Verloren Hoop Productions. All rights reserved.

Sponsored Ad:
Follow us on:
Free Newsletter | About Us | Site Map | Advertising Info | Contact Us


©2015 Inc.