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Filter your water or not?

Posted: Thu Mar 12, 2009 9:14 pm
by rlown
Some have said in other threads that they don't usually filter their water in the Sierras. I was just curious if anyone on this forum has ever had Giardia or other water-born illnesses.

I personally filter especially around lakes as most camp in places (and therefore do other things) upstream of the inlet.


Re: Filter your water or not?

Posted: Fri Mar 13, 2009 8:35 pm
by paul
I have had Giardiasis twice - once in Nepal and once in Mexico. Never had a waterborne illness from the Sierras. My basic rule (not strictly followed) is that if I can see it coming out of the snowbank, I drink it straight. On backcountry ski trips, this means I drink whatever I see! I also take into account how much use the area gets. Close to a trailhead, I'm more likely to filter. Way off trail in a remote area, not as likely. If I'm stuck with stagnant water - which sometimes happens in the sierra, mosly lower down - then I filter for sure, no matter where I am.

Re: Filter your water or not?

Posted: Fri Mar 13, 2009 10:18 pm
by Mike McGuire
In 40+ years of Sierra trips, I have never had giardia or any other sickness from the water. I don't filter. I don't take water downstream from where the mules just crossed, but otherwise not much problem Lakes are some of your more sterilized sources of water due to the high altitude UV.


Re: Filter your water or not?

Posted: Sat Mar 14, 2009 8:42 am
by balzaccom
I'll file a minority report on this one,

WE filter all of our water in the backcountry--except maybe straight from a fresh snowbank. My wife's father is a physician, and she wouldn't go on these trips without a filter. It's not really much of a hassle. We usually stop every hour for a short break on the trail, and I am usually ahead of her. I pull out the filter and pump a bit while waiting for her. And she returns the favor by cooking dinner while I fish...

I've had Giardiasis, probably from inhaling a chunk of water on a whitewater trip. It's isn't fun. It won't kill you, but it is pretty unpleasant. At the same time, i think the incubation period is probably long enough to get you home from a five day trip without any symptoms...ask a doctor about that. BUt it would certainly cut down your chances of turning around and going back out on another trip soon.

Re: Filter your water or not?

Posted: Sat Mar 14, 2009 10:30 am
by maverick
I would be willing to bet that the majority of Giardia cases in backpackers come
from not washing there hands properly after using the bathroom.
Soap and water, hand sanitizer, keeping nails cut, and properly washing cooking
and eating utensils will probably eradicate the majority of Giardia cases.
Choosing your water source intelligently obviously plays a role.
These following articles will help you make an informed decision, and also give
you insight on how to keep the odds in your favor.

Here is a link to a previous discussion on the subject:

Here is another link with a lot of info:

And another: ... n-2006.pdf

Re: Filter your water or not?

Posted: Sat Mar 14, 2009 4:07 pm
by Take-a-Hike
Wife 'n I have only been at this 5 years and finally...last trip last summer I think I'm getting to turn the corner w/her. I have to filter everything she touches to her lips..including the water she's going to boil to cook dinner with. But after countless arguements I think I have her convinced it's a waste of effort to filter then boil. I still have to filter her drinking, it's dip and drink.

I was born, raised on a dairy farm upstate NY. Drove tractor in the fields since I was about 12. At the time there was one little farm after another in our little valley tucked in between two ridges. Crick, (creek to city folk), ran down the length of our farm at low point of the valley. Needless to say everthing in between sloped to and ran off to the crick. Cows went across it in the summer time twice a day, farmers up 'n down the valley spread manure on fields that sloped and ran off to the crick. On those hot summer days as kids we swam in a few swimming holes in the crick, later on when I got hot and thirsty, guess what, I drove the tractor close, got down and dumped my head in the water and drank til I couldn't drink any more. Later if I got thirsty, would do it again. I never heard of girardia til I started backpacking five years ago. Our house drinking water there is from a spring and a well...the well is a recent addition. I can remember my mother sending off samples of critters in the spring water to places like Cornell and other university labs to test some of the floaties she found in the water. Results all came back w/advice to keep drinking the water..nothing but protein in there.

I do agree w/Maverick about cleanliness on bp trips. I wear contacts and keeping fingers/hands clean enough to take em out at night was a bugger. Eyes never forgave me first few trips, so I had to get glasses and I wear them on trips now and leave the contacts home. Because we don't carry soap, just the sanitizer, it's tough to keep hands clean. So I'll keep filtering wifes water, dipping mine.

Re: Filter your water or not?

Posted: Sat Mar 14, 2009 5:05 pm
by dave54
While giardia may be an overrated threat, there are many other potential sources of tummy terrors. Each may be slight of itself, but the cumulative threat of something ruining your trip is not to be ignored. Filtering is cheap and easy insurance.

Re: Filter your water or not?

Posted: Sat Mar 14, 2009 6:00 pm
by markskor
I was going to let this one alone, but…
There has never been one, documented case of anyone getting Giardia that can be 100% attributed to the drinking of untreated water in the High Sierra.
You cannot filter out what is not there to begin with.
40 years visiting the Sierra, some backpacking…never filtered.

Re: Filter your water or not?

Posted: Sat Mar 14, 2009 8:30 pm
by Buck Forester
I spent years exploring the northern Sierra with a Sierra Cup looped around my belt. I'd just dip it in a creek and continue on. Never filtered anything. The last few years I've been filtering most of my water, mostly because it's good arm exercise and I worked at REI and I had to recommend filters. I had to support the water filter companies and the "giardia scare craze". :evil: I guess I should be more concerned about the handful of trail mix right after I poop. Ha!

Re: Filter your water or not?

Posted: Sat Mar 14, 2009 9:24 pm
by giantbrookie
Although I am familiar with studies that show very minimal risk of getting anything from the water, I do in fact filter if the body of water I am obtaining water from is reached by a trail (or crossed upstream by one). Otherwise, I just scoop water with my old school sierra cup. Most of my off trail campsites I simply get water from a stream and don't worry about filtering.