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Public Domain Sketch from Wikipedia |
Water Purification: Filters, Pills, UV and Common Sense |
CDC Filter Standards Look for one of the following on the filter package to be sure of adequate protection against cryptosporidium: Reverse Osmosis Filtration Absolute Pore Size 1 Micron or less Tested and Certified by NSF and meets Standard 53 or 58 for cyst removal or cyst reduction Filters effective against Giardia may not screen out Crypto. Nominal pore size of 1 micron could mean many pores exceed 1 micron in diameter. |
Finding or Making Clean Water Scroll down for info on carbon filtration, ceramic filtration, UV sterilizers, purification tablets, and primitive fall-back tips. In the 70's I wouldn't have considered a water filter as anything more than a piece of gear city people would carry on a visit to the country. I carried water purification tablets but seldom used them, and I took few precautions beyond boiling water as I cooked and brewed my tea. People were concerned about Beaver Fever even then, but I spent most of my hiking time in the higher parts of the mountains where the water certainly seemed pure and clean. I never came down with any illness from it. Today I carry a filter, and even in the high mountains I'd be inclined to use it. There might be a few places where I'd decide it was unnecessary, but I haven't been to them lately. Back country trails have become small towns様ong thin chains of people passing through, who have to stop here and there to use the bathroom. There usually isn't any bathroom, and not many of those visitors have good sanitary habits. It's likely that somebody upstream from you just peed in the water, even if the water comes out of a hole in the mountain. Whether it's true that all water sources in North America are now unsafe to drink without treatment, I can't say. I doubt that it's true, or that all water sources have been tested. I used to drink from lakes where beavers swam and didn't suffer from it. If the contamination level is low, you may not. The real problem is people. Assume that people have camped upstream, and that they use streams as a toilet. I've been doing what the CDC recommends. I use a filter as a pre-cleaner. I sanitize the filtered water before I drink it. The best disinfectant is boiling. My purifier is a Svea 123 and a pot. The CDC says boil for a minute, or three minutes at high altitudes. Be careful of untreated water remaining in storage containers and droplets on the rim of the pot. The only time I've ever been sick from back country water, the cause was cross contamination. |
Of the two big names in the back country water filter industry I prefer Katadyn. With good choices for both hikers and third world travelers, Katadyn offers a full range of products based on activated charcoal filtration, ceramic filtration or both. Katadyn claims that even their ordinary hiker/backpacker models filter down to 0.3 microns and remove 99.9 percent of giardia and cryptosporidium organisms. I'll still boil the water. Hiker and Hiker Pro from Katadyn are in essence the same water filter. Hiker Pro includes an extra connection method which lets you fill a hydration bladder through the sip tube葉his way you avoid having to take the bladder out of the hydration pack or backpack compartment. Filtering capability for both is exactly the same. One minor problem with the Hiker Pro won't be a problem if you know about it beforehand預n extra fitting at the bottom snaps off easily if you put pressure on it while pumping. Be aware. A more serious issue is that without disinfection at home between trips, the filter could actually grow the things you don't want to drink. Pump some chorinated water through before putting it away. The output flow rate of one liter per minute is plenty to supply two people. The pre-filter helps keep large debris out of the pump and extends filter life. In reasonable conditions the replaceable filter should last for 750 liters. Weight is about 11 ounces葉rade that off against having to carry extra water and it's a weight savings. The carbon filtration removes dangerous chemicals and yields water with good flavor. |
Ultraviolet Sterilization--the SteriPEN There's a very interesting idea at work in the SteriPEN葉hat you can take water that looks clean, insert this very portable and convenient device in a full container of untreated water, and pressing a button makes the water safe. The concentrated UV light kills bacteria, protozoa and viruses. Swish the protected bulb around until the PEN signals you're done, and you can drink the water right then. People use the SteriPEN and have good luck with it. It's a great idea. In the real world there are of course problems. The SteriPEN has little effect on chemical pollution. In cloudy or muddy water the UV light will not completely penetrate the container. Only small volumes of water can be effectively treated with the tiny portable SteriPEN's. If debris shields micro-organisms from the light幼lumps of dirt, floating vegetable matter, or other disgusting things葉he UV has no effect. Water must be clear before treatment really works. SteriPEN does offer some attachments with this in mind用refilters clean up what goes into the bottle. Filtering with the tiny prep system SteriPEN offers only works if you're patient. A far better idea is to use the SteriPEN in conjunction with a good micro-filter. The Hiker Pro, for instance, provides a large amount of clear filtered water very quickly. Viruses and a few other critters might sail on through it. Using a SteriPEN finishes the job. Anything battery powered is marginally trustworthy--batteries go dead and connections fail. The original SteriPEN used four AA's預 lot of weight to put in your pack. Newer ultralight versions use two CR123A's. Total weight of the kit drops to four ounces. SteriPEN even offers a solar panel travel pack for recharging the tiny power cells, if you aren't sure how often you'll find CR123 disposables. How well that works will depend on how long you can hold still. Perfect weather and continuous direct sunlight will be required, and the process will take many hours. Taking along extra batteries makes much better sense. With a normal workload and good luck, you won't need them. |
I'm not against MSR filters but I haven't used them myself. I haven't used them because after doing what research I could I decided I liked Katadyn better. MSR's do have the advantage of being ceramic filter based from the start. Buy a cheap MSR and you still get ceramic filtering. The lightest models really are light. But, people have problems with them. If you have an issue with an MSR filter, the first thing to do is take the ceramic filter out and clean it. The wafer design is very fragile. People have broken them by simply trying to take them out for cleaning. Considering that and the bulky pump handle design, I decided I'd rather go with a carbon filter from Katadyn. I'm not willing to trust my health to the output of any filtration system. If I have to carry one, I want one that's tough. If you like the look of MSR, go for it. This is a new industry and MSR competes by fixing problems. They may eventually thrash out the better idea, but I don't feel they are quite there yet. |
Katadyn Vario Switch prefilter to ceramic for murky water, to glass for clear water. Better flow rates with the glass/carbon combo. Better filtration and longer life with the ceramic/carbon filter. Heavy. Weighs about a pound. |
CDC Articles on Water Quality A Guide to Drinking Water Treatment and Sanitation for Backcountry & Travel Use A Guide to Water Filters Emergency Water Treatment |
Water Purification Tablets Let's return to where I began in the 70's, when to be sure I wouldn't get the squats I just dropped a couple of iodine tabs in my canteen and shook it up. I didn't know that it isn't always effective and I didn't wait the required amount of time for proper sterilization. I didn't get sick. Maybe water was cleaner back then. It sure did look cleaner. Iodine and chlorine are just emergency measures now, things to do when it's the best you have. Now we know that they have limited effectiveness--in fact you can read whatever you want to believe, written by people who seem to be experts, and the verdict will change from article to article. Don't double up and use the shotgun chemical approach. Instead, use chlorine dioxide. By itself it's an imperfect method, but in combination with filtration, chlorine dioxide provides safe water. Or maybe safer water--you still have to follow directions, wait the required period of time, and treat water that's relatively clean already. Filter first. Disinfect later. If all you can get is iodine, use it, but use it carefully. Iodine is poison. Ingesting too much could be deadly. See the CDC links I've posted for precise instructions. |
The problems with the Hiker models are common for filtration systems in general. You might get a filter that works fine or you might get a filter that clogs after pumping three gallons of pristine stream water. No product is as yet immune to these issues. Hikers understandably get very angry about things they buy to depend upon, only to find out immediately that they can't. The usual solution is to buy a different product from the competition when you get home. That won't always eliminate the problem. Filters are getting better and both Katadyn and MSR work to resolve these issues. What can you do to avoid trouble? You could carry an extra filter cartridge. You could be prepared with a backup system like boiling or disinfecting. If the filter does clog, don't force it. You could break the pump. Use your alternate method and deal with the filter at home. Katadyn's ceramic filter systems outperform the carbon filter Hiker and Hiker Pro in some important ways. Total output significantly increases compared to the carbon versions and filtration is more reliable. Particle removal down to 0.2 microns means no giardia nor crytosporidium gets through. Silver coating on the filter prevents buildup of contaminants between uses. The Katadyn Mini Ceramic Microfilter could be the ultimate best choice for backpacking. Total weight of only eight ounces makes it very tempting. The flow rate drops to half a liter per minute, enough for one person and even two if you have patience. Total output in the ceramic filter's lifetime jumps up to 2,000 gallons葉en times the output of one Hiker Pro filter. Drawbacks? Ceramic filters break. Don't drop the Mini. Some people don't like the flat taste of water that's run through a ceramic filter, and ceramics don't remove chemicals as carbon filters do. Willing to carry more weight? Then step up to the Katadyn Combi. The Combi's ceramic filter yields up to 13,000 gallons of clean water and a flow rate twice that of the Mini. A replaceable carbon filter can double up the protection, removing those pesky pesticides. The carbon filter is optional. Leave it home if you want to save a little weight. Weight and size are an issue葉his twelve inch tall pump weighs 21 ounces including all the accessories. Think bulletproof, and you get the Katadyn Pocket Microfilter. Output and flow rate match the Combi's but without the optional carbon filtration. In spite of the shift to machined aluminum parts, weight drops to 20 ounces. The critical ceramic filter core receives more impact protection and there's less chance of deformation of the housing--something that could cause leaks in the plastic body builds. The International Red Cross provides the Katadyn Pocket filter to all its field workers葉here's no better recommendation than knowing professionals use the same machine. |
Primitive Water Filters Having been through military survival training I recognize the filtration system shown in the sketch below. It's a fine example of something designed by somebody sitting behind a desk in the Pentagon. Actually |
most of what I was taught in Army survival training turned out to be pretty impractical, and fortunately I didn't have reason to use it while in the military. After my discharge I tested some of it and found a lot that doesn't work. So let me point out some real world concerns regarding the three tier water filter shown below. First, it's a pain to put together. There's a lot of weight involved and it will probably just fall over when you have to leave it for five minutes and do something else. Throwing a loop around the feet of the tripod will help stop them from spreading, but the end result isn't worth the trouble. The grass filter does nothing. The cloth does all the filtering and the grass just floats there. The sand filter might work but if you pour too much water it just flows past the sand. Same problem with the charcoal, to really pass the water through the charcoal instead of around it, the charcoal needs to be compacted and the system needs rigid containment. So what you'll probably get from this is dirty water with sand, grass and charcoal in it. Before you started, you just had dirty water. What the heck, boil it and you'll be ok. |
If you want a gravity filter that works, you need a big filter in a solid container. An old five gallon bucket with a hole punched in the bottom serves; a clean 55 gallon drum is a lot better. Line the bottom with cloth if you have it, otherwise the filtering materials will come out with the water. A layer of finely crunched charcoal won't hurt, but you'll get nasty looking water for awhile. Cover that with clean sand, and for a coarse upper filter use pea gravel. Stay away from the grass unless you've got nothing else. The only thing it'll filter out is sticks or dead bugs, the big stuff you could actually scoop out with your fingers. Leave a couple of inches of empty space at the top so you can fill that with water and let it drain. Don't expect anything really clean to come out the bottom. Although this will actually do some filtering, you'll probably get results just as good by filtering water through a piece of your clothing without all the voodoo technology. The method I've actually used most successfully is a filtration pit. If the source of your potential drinking water isn't too nasty--say, nothing worse than Lake Erie, full of dead clams and other things you don't want to know about--dig a hole onshore, down to below the waterline, and let it fill with groundwater. That's about as filtered as anything you can rig on your own. Much much easier is to look for naturally filtered water--drips and seeps in caves, under ledges or in damp creek beds. Dig a hole under the drip and line it with plastic if you don't have a container. If the soil is fine clay you won't even need the plastic. Water that runs through natural substrates may not be pure, but it's already filtered. Creekbed results are iffy. You might have to do more digging than is possible to reach the water table. If you hit mud, you're there. |
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