Water filters

Half Dome – Yosemite Musing

The most critical part of your Half Dome hike is water treatment. The waters in the Merced and other sources in the park contain Giardia and Cryptosporidium. These are protozoa that, when injested, are intestinal parasites. That means in about 7-10 days after you return from your hike, you may get diarrhea. If untreated, the consequences can be deadly. A friend told me a buddy’s son got it and did not get it taken care of . . . and died. Yikes. While many claim that they have drunk the water for years with no ill effects, why take a chance? E-Coli from feces is a primary source. There are all kinds of animals (and people) to contribute to the problem. Boiling water works, it takes too long and is impractical on a day hike. Chemicals take at least 30 minutes to work and may not inactivate all protozoa. I suggest using a water filter pump. The three types of mechanical devices to treat water, their effectiveness and Micron rating are: 

  1. Filter – Removes Giardia, large protozoa and some bacteria. (1.0 – 4.0 micron)
  2. Microfilter – Removes microorganisms, including protozoa & bacteria. (.3 – 1.0 micron)
  3. Purifier – Removes microorganisms, including viruses. (.018 micron)

 Read the box carefully. The nomenclature can be confusing. The street name for these devices is “water filter”. However, as you can see above, the technical name implies distinct capabilities.  A “water filter” does not do the job as well as a “water purifier.” Filters can remove bacteria and protozoan cysts. Purifiers can do this and remove viruses. In the Sierra (and most of the US) viruses are a nn-issue. Because of the strict EPA requirements, a true “purifier” is hard to find. A 0.2-micron pore size or less is regarded as the optimum. Be sure to read the literature to make sure that Giardia and other microscopic pathogens (disease-causing agents) will be removed.

Unrelated thought worth quoting: “Bottom’s up.”  

*Mr. Half Dome – Rick Deutsch – www.HikeHalfDome.com


11 Responses to “Water filters”

  1. John Lauer Says:

    I have a Katadyn Hiker filter. For Sierra water, is this likely to remove nearly everything harmful? I know the trick about attaching coffee filters around the intake to take out initial sediment , also… Any need to drop in iodide or chlorine?

    • mrhalfdome Says:

      Your Katadyn will do just fine. Keep it off the bottom to avoid sediment…the pre-filter takes care of bigger stuff….it is rated for giardia & crystosporidium… Add nothing. Do nothing.

      Don’t suffer paralysis from over analysis.

  2. John Lauer Says:

    Looking like a HUGE YOSEMITE HEATWAVE! Me thinks the cables will be up for Memorial weekend!

  3. John Lauer Says:

    I will add the coffee filters so less sediment gets in… they are cheap as dirt, otherwise I would not bother. I read if you did use a water source with heavy sediment, you can put water in a pail like a half hour, let the junk settle, then take the good off the top… I imagine the lil SPRING off Half Dome trail is nearly free of sediment!

  4. John Lauer Says:

    SO… RICK, when are you going up the Half Dome trail again? If you are not doing the Diving Board May 16th, are you going later this Spring? You recommended hiking Glacier Point Trail. I did part of it last year. I think I would rather spend the time driving to the Point, then ride my mountain bike around. I will probably hike a ways down the trail. I may hike down the initial gully of the Ledge Trail. I know better than to go far.

    • mrhalfdome Says:

      My next HD trip is June 23. I will be teaching Nordic Walking on Crystal Cruise lines in the Middle east most of May.

      Mt bikes are not allowed on Yosemite’s hiking trails. Trail cutting is not allowed. Stay on the trails.

  5. Alan Hudson Says:

    Hello Rick,

    I will be (trying) hiking up Half Dome with my teenage sons at the end of June. I just bought 2 liter Camelbacks and will carry extra bottles. How much water do you recommend we carry. Are there water sources above Vernal Falls? Also, we will be staying in Curry Village for two days. I just read where you recommended the 700s for tents. Why?


    p.s. I will let you know if we make it to the top.

    • mrhalfdome Says:


      I hope you are training for this hike. You should know in advance what your water requirements are. I drink 7 quarts all day…I’m about 200 pounds. I do not like to carry my water. It weighs 2 pounds per quart and gets hot from your body and the ambient air. You can pump filter out of the Merced and the Little Spring – both above Vernal Fall. See my book for details.

      The 700 series is at the far eastern end of Curry Village and away from all the riff raff and noise. It is also closest to the Happy Isles trailhead that you need to be on. Good luck!

    • John Lauer Says:

      Of course, stay optimally hydrated for at least a couple days before the hike, and that will help too!

  6. John Lauer Says:

    No Mountain Bike on the trails… ON GLACIER POINT ROAD.

  7. Tom Says:

    Alan-and I’m sure Rick would agree- the man has hiked this thing 25 times, myself half that-you don’t want to carry 30 pounds of water between you and your son. Fill your hydration
    packs (4 pounds), and take a (1 pound) water filter. Read: math. John Lauer: yes coffee filters
    are cheap and lite, but very unessesary. I personaly try to leave the trailhead with only the stuff I NEED. Buy the book.

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