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Is Snow Melt Safe to Drink?

If you melt snow for drinking water in the winter, do you need to boil it for purification?


If I plan to drink snow melt in the winter, do I need to boil it for purification first?

Submitted by - Dave - Port Washington, WI


Drinking water made from clean white snow melt is generally considered safe because pathogens don’t usually survive in it. But that’s not always the only consideration. In areas with lots of traffic like outside of well-used huts or in patches of late-season snow there may be added pollutants that you’d want to filter or otherwise clean out.

For the best results, pull fresh, clean-looking snow from a designated “drinking snow” area away from traffic zones, toilets, or dish pits. Also, add a little water to the it before heating up your melting pot, which can scorch and taint the water with a bad taste. Boiling water, which is the most effective method for disinfecting it, is often part of making coffee or warming up in winter, so if you do end up heating the water to that point you’ll get some peace of mind no matter where you got it.


  1. rangewalker

    high-sierra-fan has the high ground on the toxins left in pinkish “water-melon” snow that will not filter or boil out but they are recognizable.
    In the spring desert and sagebrush steppe that I frequent in Wyoming a number of critters visiting and using the small residual drift pockets of snow defecate all around or on the sites. So melting, screening through bandanas, and then filtering is always called for. the trouble is worth it as many these areas are just not hospitable in the depths of summer or winter.

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  2. high_sierra_fan

    There might remain whatever toxins the dinoflagellate red algae have produced in an analogy to marine red tides. Small toxin molecules wouldn’t be filtered by a filter designed for micro organisms and a rolling boil wouldn’t necessarily denature them.

    Watermelon snow is easy enough to see and avoid, since it’s patchy, that I’d probably just avoid it.

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  3. Doug

    Re the red snow question (indirectly) 1. filters remove any biological pathogens larger than viruses, (and there are virtually no pathogenic viruses that survive in the wild in NA) 2. boiling kills all biological pathogens, 3. chlorine (and iodine) kills all biological pathogens smaller than protozoans etc. in 5 minutes and kills the big things in four hours. Simple as that. So a filter is virtually guaranteed to be safe, you can follow it with chlorine to be sure. Boiling is 100% safe. And chemical is 100% safe if you wait 4 hours and are careful about making sure all the water is treated, e.g., none is left untreated at the threads in the bottle etc. UV is also supposed to be 100% effective and again requires some care to make sure all water is treated. So I don’t know whether red snow algae *requires* treatment, but boiling or any of the other treatments would certainly be *effective*.

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