View Full Version : Purifying Water

2003-02-19, 20:24
On the Camping Lite board I read with interest some discussion about Giardia and other beasties and diarrhea and the various ways to treat water.

Someone quoted in the blind a study done which showed that there was essentially no difference in the gastroenteritis or the Giardia rate regardless of how you treated or did not treat water.

The original numbers actually come from a book by Roland Mueser called "Long Distance Hiking, Lessons from the Appalachian Trail" where he took information from 136 Thru hikers. Reference that book, p 95-6.

He comes to the conclusion that the source of giardia among AT hikers is likely not their water... a pretty revealing answer, frankly. He (with some evidence from other researchers) thinks the real cause of Giardia is more likely poor hygene. (To be blunt, getting feces in food by not washing hands.) Others have even gone to the extent to suggest that the poor beaver (often blamed for giardia in the wild) may actually be catching the stuff from people!

Well, this has led me to reconsider my water options. I am leaving my Sweetwater filter at home during my next canoe voyage in the BWCA. I will take Polar Pure for places where I can not get water from the middle of a clear lake. I will also take some hand cleanser in my toilet paper zip lock and use it. I will also be a lot careful about food prepared by others. Backpacking, I will use polar pure for any water for which I do not know the entire watershed is free of human outhouses and septic tanks. This is more to prevent the chance of catching viral hepatitis than Giardia.

I doubt any of the outfitters/authorities will come out and say that filtering water is not necessary, for fear of a suit. But we users can look at the evidence and make up our minds based on real facts, not the current "expert opinion" from the forest service. Thoughts??


2003-02-19, 21:10
Originally posted by flyfisher
But we users can look at the evidence and make up our minds based on real facts, not the current "expert opinion" from the forest service. Thoughts??

By real facts, do you mean those from unscientific questioning of a few thru-hikers? No thanks, I'll make my mind up from the "expert opinion". BTW, the forest service is not alone in their opinion.

Lone Wolf
2003-02-19, 21:34
I've hiked 16,000+ miles on the AT and never once treated or filtered any water. Never been sick either. And don't try to tell me I'm a "carrier" of giardias. I grew up on city/treated water. Getting water borne diseases on the trail is rare.

2003-02-19, 22:59
By real facts, I mean to look at this survey, and other evidence as it may exist, and collecting new information as necessary, and looking at the original studies instead of quoting to each other the analysis printed in government brochures.

An example: Everyone knows that spinich is high in iron. Popeye taught us all that it is. The US government books and all the dietary books show that it is absolutely chock full of iron. Except it is not... no more than celery. But back in the early 1900s a government publication had an error in printing that showed that spinich has 10 times the iron it actually has. Most of the text books all go back to that original table and perpetuate the error.

Another example: Everyone knows that milk is a wonderful source of calcium. Except it is not really as good as beef nor anywhere near as good as sardines. However the milk industry has been pumping milk as a calcium source for years and we all *know* it is a best source.

OK, enough off topic, to get back to Giardia:

I am not an advocate of taking the position of any health guru on any of these topics. However, I learned a long time ago in medicine to "study a study and test a test" and to evaluate whether the conclusions reached by the author make sense. I happen to believe, based on several published studies, that much of the written standard "knowledge" on Giardia may not be backed up by good science. You may not reach the same conclusion, and I am interested in the reasons you reach your conclusion. I point out the survey done by Mueser, not because it is a great study, but because it got me to consider an "outside the party line" on Giardia and because it was quoted on the other board without reference.



SGT Rock
2003-02-19, 23:11
From what I've read, and that is a few sources, the water is way down on the food chain so to speak. For years there were no filters and no one had many problems, but along came the filter and now it is the accepted wisdom that you absolutly need a filter, at least by a lot of people these days.

1. Given the real scientifc evidence that your filters actually get less protective than simple iodine over time (lab study, not some out of the air factoid) then what is the real value of a filter? Well, it must be the placebo effct.

2. People with filters still get sick as much as people that do absolutly nothing statistically. So, what is the real benifit of a filter.

3. As I said, we went for years before companies started making filters. We used treatments, boiling, and simple selective drinking from sources based on experience and judgement. So again, where did the need for filters come in?

4. Lots of studies say washing your hands, not sharing food containers, and not sharing food like GORP are the best defenses against getting sick. Hand wash for a week weighs a couple of ounces. So if hand washing is more important than filters - why not the anal retentive need for hand washing and clean towels like some people have for their filters?


Bandana Man
2003-02-20, 00:08
Most hikers here and other sites seem to scoff (sp?) at carrying a filter yet I'll continue to carry mine anyway. I've had some pretty nasty intestinal stuff in the past. Don't think it was giardia but if giardia is anything like what I had -- I don't want it again! I've tried iodine and some other stuff (years ago) but didn't like the taste it left in the water. Water treated by my filter just tastes better to me.

BTW, my uncle has a farm near Thurmont MD not many miles from the AT. Years ago when my grandfather was alive and ran the farm, there were two springs where he got all his water because the farmhouse had no running water. I used to drink water straight out of the stone-lined spring. It was cool and delicious -- never tasted any better water! Today, the springs cannot be used. The water was tested and contains giardia. So maybe there is some truth to the reports that giardia is spreading. I know this is anecdotal and not hard evidence but it makes me want to err on the side of caution. But that's just me -- everyone is different!

2003-02-20, 00:17
well, i've drunk the water in over 75 different countries, most of which you'd consider third world. i never got sick either. does that prove anything? no, it's nothing more than anecdotal as is everything i've seen here. go ahead, filter or not. sometimes i do, other times i don't, but i'm not swayed by useless studies being passed off as real facts.

SGT Rock
2003-02-20, 00:42
I've had some nasty ones. I got this one in El Paso that lasted a week and a half (talk about miserable) and I was only drinking piped water. The cause was most likely training in the sand where hundrends or thousands of soldiers have pissed, pooped, and done every other thing upon, then probably not washing my hand before eating my MRE. Even after it was gone it took me a long time to recover. The times I have seen bad stomach bugs on trails I could see it coming for the person from eating with dirty hands.

Anyway, even in the swampy Louisiana training areas I only use iodine and still live, the AT water has to be better than some of the festering swamps I've got my water from. I'll keep washing my hands and using nothing or iodine.

2003-02-20, 08:40
Lone Wolf,

Great experience! What do you do to get water on the trail?

Before the great interest in giardia, I used my father's admonition well: drink water from a gurgling brook which is well aerated and where one can reasonably know there are no septic tanks up stream.

With your success, I'd be interested in your approach.


2003-02-20, 08:42
there have only been a few times on the AT where i thought i absolutely had to filter water. mostly this was because a very slow running spring was stagnant or muddy and i was out of water (my own fault, after passing up perfectly good springs). just needed a filter to get the mud out. nothing like louisiana for sure!

there have been places on the AT where you are warned not to drink the water. i think these signs are posted for hikers' protection rather than to limit someones liability. i guess, if you wash yer hands, this water is good too.

2003-02-20, 09:11
A lot of good posts here. Is the water safe to drink or not?

Do hikers get sick from the water, or from poor hygene or from sharing food and drink? No one knows for sure. Bud, it's the water that usually gets blamed.

Water sources along the trail are not tested, and signs are posted accordingly. So we don't know if a source is pure or not.

Like many others, I suspect that the water is purer than we are lead to believe. But, the bottom line is that while giardia wouldn't kill you, you wish it did. So, until someone comes out with something definitive, I think it's prudent to treat the water.

2003-02-20, 09:13

I assume no offense taken, certainly none intended.

I agree with your admonition not to take the single study and its analysis as fact. I also am leery of taking the other studies' conclusions as gospel. I do not have the resources to do a thesis on giardia at the present, but together we all may have the energy to make sense of the many opinions expressed from many sources.

There is a good deal of disagreement about giardia out on the net at the moment. Some of it is good science, some of it is just opinion. I (and I assume we) have been around long enough to remember how the general medical consensus has changed on a topic from time to time. The present generally accepted admonitions to use filters on wilderness water to avoid giardia may stand the test of time or may pass away. For many other areas off the AT, using an antiviral is probably much more important than filtering for giardia.

Anecdotal stories are a weak, but not useless source of evidence in building and maintaining a doctrine. They are a useful source for challenging the sometimes overly accepted present state of understanding.


p.s. Example (off topic) When I trained in the 70s, everyone knew the cause of ulcers and everyone treated them much the same - with compounds that protected the lining of the duodenum or decreased the acid or both. There was a little report from private practice of a fellow in Oz treating ulcers with an antibiotic! What a crock! When an Australian doc first mentioned this to me in 1990, I told him what I thought of his reading his parochial literature. ..... Of course, now everyone recognizes the Aussie was correct and everyone else was wrong.

"I find, over time, that the person I most violently disagree with, is me. How I could have held the opinions I used to hold is sometimes inconceivable to my mind today. I think most perceptive learning adults should sometimes find they hold their past views in contempt too."

Happy walking!

Lone Wolf
2003-02-20, 09:36
flyfisher, I obtain water on the trail the same way all other hikers do. I just choose not to filter or chemically treat it. Although if there are a lot of floaties in the water and it's off color I'll pour in some grape Kool-aid and shake it up. Out of sight, out of mind!:D I don't buy into studies either. It's funny watching folks go thru they're filtering routines. I love walking up to a spring when 3 or 4 hikers are hard at work pumping water and I just stick my bottle under the pipe or dip it in the spring and just drink. No worries mate!:)

2003-02-20, 10:10
OK, here are some anecdotal data...

A quick search of the net and I found the following articles... All but the last are about how you MUST treat the water. One points out that it is necessary to filter snow melt. One (from a national park) says that you should filter the water and then use chemicals.

The last article is the only footnoted article. It is the only one which (to me) goes into important details, like how many spores does it take to get giardia and how many are in the source..

I must admit that I have not gone to the sources in the footnotes (yet). Only then would I begin to feel I have really examined the topic. I would also like the opportunity to examine about a dozen other articles of the same quality and compare them to one another.

Here are the sources I looked at this AM for your amusement:

"Dont get Beaver Fever!"

"Giardia Club:"

"Compass Monkey"


"USDA Forest Service Stanislaus National Forest"
Chemically treat filtered water

"Hiking First-Aid"
The reason I have placed this subject on my web site is that it is a highly increasing problem. If my sources are correct over 80% of the world's surface water has this parasite.

"Unfortunately Giardia spores are present in many streams and lakes in the high country.
INYO National Forest - personal page"
No matter how clean appearing the water is, boiling or filtering is recommended to remove spores or other microscopic critters. Giardia requires treatment by a physician and in some cases can cause hospitalization. Snow should aiso be treated before being used for water.

For an alternative view:
Giardia Lamblia and Giardiasis
Footnoted article by Robert Rockwell, PhD

Interesting assortment? I hope y'all had fun thinking about the problem. I had fun finding the articles.


2003-02-20, 11:04
Couple more referenced articles about giardia:

Both question water as a source of significant illness:

Cyst acquisition rate for Giardia Lamblia in backcountry travelers to Desolation Wilderness, Lake Tahoe.

This was a prospective study of backpackers, and though the number of participants was low (41) the results are informative.

Maybe the best of the articles:

Giardiasis as a threat to backpackers in the United States: a survey of state health deparments

A couple quotes:

"It appears to be common wisdom among outdoor recreationists in the United States that there is widespread fecal contamination of wilderness waters. This has led to the perception that water-borne enteric infections, with giardiasis as the prototype, are a major threat to users of the back country. This survey suggests that if this consensus is real, it has escaped the attention of professional epidemiologists in health departments throughout the nation"

"Neither health department surveillance nor the medical literature support the widely held perception that giardiasis is a significant risk to backpackers in the United States."

"Giardiasis and similar enteric illness in develped nations are overwhelmingly spread by direct fecal-oral or food-borne transmission, not by contaminated drinking water. Given the casual appraoch to personal hygiene that characterizes most backpacking treks, handwashing is likley to be a much more useful preventive strategy than water disinfection!"


Ready for the other side...


2003-02-23, 14:12
My question is: Is giardia (and all it's cousins) actually on the rise? - or - have our human immune systems been disinfected, decontaminated, and sterilized, into quivvering masses of defenseless flesh, by modernized "civilization"?

Sixty years ago, my mother and I moved in with my grandparents, while my father drank the sewer-water on German and French battlefields, for nearly four years.

My granddad raised chickens/eggs for a living, and the "house-spring" was in the center of the chicken yard, merely fenced around, and over, to disallow the chicken's immediate contact with the water. Nobody ever got sick, including all the aunts, uncles, and cousins who visited regularly - some who were farmers and some from towns. My old man said he and most of his comrades-in-arms threw away their iodine tablets - because they "tasted" worse than the water. Apparently, they didn't get sick, either (although, I know, some did). I ran a short trap-line, down through a pasture and woods, that also kept a herd of cows. The little stream was full of muskrats and mink, and I'm relatively positive that those ancestors of today's wild critters (and domestic ones) didn't run 200 yards from the stream, and crap in "cat-holes". When I was thirsty - I drank from the stream, as long as the cows were down-meadow. I didn't realize it, then, but since our house was down-hill from the town (which strung out on the ridge), all the cess-pools, and outhouses on our side of the ridge, were also draining into the watershed.

Today, after being chlorinated. and antibiotic'd into abject immune-system woosiness, I wouldn't even think of drinking directly from a stream, even tho' it "might" be as pure as Ice Age snow. I have an ultra-violet purification system on my well-water, which may, or may not, be doing what they tell me it is doing. I'm hypothroid, so I can't safely rely on iodine, so, for my hiking, I have have chosen to use a PUR Guide filter (alone), and take my chances with the rest.

I'd be interested in hearing what you physicians have to say about my feelings regarding our immune-systems having been "purified" into relative uselessness.

I still rely on that age-old wisdom of Will Rogers: "Never drink downstream from the herd".

2003-02-23, 22:32

There is something to be said for the immunity of many of our forebearers. They either developed immunity or died trying.

I don't think it is so much that with our safer water supplies and food and all that we have immune systems which are weak, just not exercised as much as others.

After all, it used to be common in the summer to lose several people in every small village due to contaminated water - usually cholera or salmonella. Fortunately, most of that was overcome at the beginning of the 20th Century by the Public Health Movement.

2003-02-24, 00:36
I have diagnosed giardia in a number of children in DAYCARE, so as far as I am concerned, it is every where. my filter only weighs 11 oz anyway, and so if it is not neccessary then it is a luxury I don't mind carrying. besides, there are other beasties in the water and it would be my luck to be the case report for the first american clonorchis infection.


that being said, if you do get it, odds are you will clear it on your own, and if you can't a simple course of Flagyl will get it.


p.s. wash your hands.

2003-02-24, 09:13
Actually, from what I read while getting together all the information on giardiasis, daycare is the most likely place to get it. Ages 0-5 are the most likely to have it. Second most likely are those 25-35 (Those who have children in day care). Swimming pool water with babies in it is a great spreading ground for it.

And wash your hands before making tossed salad. And when I offer you some GORP, please do not be offended when I pour it into your hand instead of having you dig into my bag.

2003-02-24, 10:48
I'm not exactly obsessive/compulsive, but I wash my hands very frequently, especially when I'm around places where the public congregates. We also share our house with three cats and a big, stupid, dog, and I am constantly harranging my wife and daughter about washing their hands after handling the pets, and I'm insane about admonishing them for letting the dog lick their face or hands. It took me years before I could stop my wife from allowing the dog to finish table scraps of a dinner plate, after a meal.

I've seen campers who sleep with their dogs; let their dogs lick their mouths and faces; lick out their cooking/eating utensils (which are then usually rinsed with warm or cold water, and wiped with whatever is handy).

Not only does a dog use it's tongue to clean it's own ass and genitals, but it has been my experience, that a dog will eat - with relish - any pile of feces it can find (except, perhaps it's own). I normally get the lecture about some magical enzyme or natural disinfectant which makes a dog's mouth akin to freshly sterilized operating room. Hogwash!

We are constantly, reassured of this fantacy, by TV commercials, showing "Good ol', lumbering, Buck, French Kissing, mom and the kids. This usually is accompanied by a warm and fuzzy "Ah-h-h-h-h-h-h" from viewers.

Having not done any "scientific" research on the subject, I'll admit that this is only conjecture, but if I were to look for a source of the Girdia/other Icky-Nasties up-rise, I'd start inside good ol' "Pure-Mouth's" mouth. Seems to me that after the family carrion-eater just licked the over-flow from baby's diaper - then cleaned the Pablum from his face - then Frenched all the siblings, on their way out the door for the day-school car-pool, there just might be a connection.

Of course we can't bad-mouth (pun intended) the great human institution of "at least one dog in every kitchen". but, think about it, next time you let ol' pooch slobber in your cook-pot, or on your face, or drool on your sleeping bag, next to your mouth. The reason he was smiling when he came back to the trail, from a little side-venture, just before dinner, wasn't just because he was so happy to see you. He had probably found another hiker's cat-hole. Umm,Yummy!

2003-02-24, 11:34
No argument here Griz...

I got exposed to dogs and cats enough as a kid that I am now alergic and can not have them in the house... not that my kids and wife don't beg for a critter in the house every few weeks (for the last 25 years). We now have a bunch of barn cats living outside, eating mice, leaving them on the front steps, etc. But no dog licking.

Fact is, I use cat pics a lot, because I think they are cute, the pics that is.

So for y'all that miss a dog lick, here is one that will not make you ill...


2003-02-24, 14:11
According to this site up to 70% of dogs carry giardia in their mouth. Read all about it here: http://www.vetinfo.com/dgiardia.html

2003-02-24, 14:36
Incredible! I guess I'm not as dumb as some people think I am. I always knew that dog should cooked about the same as pig. I think I'm going to start cooking it even longer, after reading that. Although I think Tabasco is even better than Iodine. Hmm? I wonder how it would work in water? Sure would taste good.:p

Lone Wolf
2003-02-24, 14:52
Can any of you experts explain why one doesn't get sick while swimming? We've all gone swimming in lakes, ponds, rivers, and streams and surely you ingest some of that water. All this giardia stuff is more fear and paranoia and hype by these filter companies.

2003-02-24, 16:37
no, and I have often wondered. I just like my water without "pulp" so therefore I filter. conditioning I suppose. But I am not terribly preachy about the subject either. If you get it it is easy to treat and (unless immunocompromised) not exactly life threatening. mainly uncomfortable and inconvient.


2003-02-24, 17:00
For Lone Wolf and Sundog,

Damned good point. We don't think about filtering our swimming water. Hell, I've even pissed in the lake once or twice. I mean, let's face it, who hasn't? Not that I recommend drinking from a registered sewer, but good point Lone Wolf.



2003-02-24, 17:21
I certainly not one of the physicians, here, but I believe the reasons are pretty apparent. Everybody's immune system is likely different in some ways. Personally, I've never followed 500 people home from a lake or swimming pool, to monitor them for a couple of days to see if they got stomach cramps, or became nauseous. I'm sure that some probably do, but even then, they'd probably blame it on Aunt Louise's potato salad, or the eleven hot dogs they wolfed down at supper, before they'd think of the 97 kids whizzing in the pool, or the cadaver rotting away at the bottom of the lake.

My daughter can carry the cats around her neck - no problem. If I pet one without washing my hands, before touching my face, my eyes swell up, in seconds. Some folks are allergic to poison ivy, others can rub it all over themselves. Most of the kids who swam with the floaters in city creeks, back when I was a child, didn't get polio - some did, and it wasn't pretty.

I don't have anything to prove, anymore - I'll filter it before I drink it.

2003-02-24, 17:54
There have cerainly been cases of 'swim" transmitted water-borne pathogens.

2003-02-24, 18:27
LW, I just don't swim with dogs.:D

2003-02-24, 21:17
Originally posted by Lugnut
LW, I just don't swim with dogs.:D

I don't anymore :D

went swimming with my first wife and it caused all kinda problems:rolleyes:

2003-02-25, 10:18
Actually a number of cases have been reported from swimming pools, usually after a child has a "fecal accident".

For a thorough article from the UK on this, please see:


Among the references, most of them have hyperlinks to the original articles or to their abstracts. For many of you this will be much more detail than you are interested in... but for the compulsives.. and I won't use the other term for that because it is too good a double entendre... there are a lot of leads to track down.