Take the 2-minute tour ×
The Great Outdoors Stack Exchange is a question and answer site for people who love outdoor activities, excursions, and outdoorsmanship. It's 100% free, no registration required.

I was just reading this question What is the safest way to purify water?

Now I walk a lot in Snowdonia in North Wales and on occasion I drink from mountain streams. I've even camped next to mountain streams and used the water as my main water source.

I haven't used any purification tablets or boiling (generally) and suffered no ill effects. I always ensure the water is fast running and 90% of the time it's fed from mountain springs, so I've always assumed it's safe, in fact I'm sure I've read it's generally cleaner than most tap water!

I'm not sure where I picked up this information, I'm pretty sure my Dad used to do this.

There will be very limited chemical pollutants (from fertilizers, etc.) in the water as the area has virtually no arable farming.

Mining is probably the worst potential pollutant but I always check the source of the water(I've been walking in the are since I was very young and know the sources of most of the streams)

Am I mad or risking my health?

share|improve this question
It would be nice if someone wound up some numbers. In this regard, IMHO, being hit by a car is the unit measure of risk - if something is a couple of digits less dangerous than cars, it's livable with. –  Vorac Jan 9 at 10:22
Yeah, this is my point. I've always thought of water purification for something to do in stagnant or slow moving water of questionable quality. I'd never think to do it in a fast running mountain stream in a National Park. Reading that article made me wonder am I in the minority? What are the stats on this. –  Liam Jan 9 at 10:26
@Liam I think mountain water is pretty safe. In California, we are careful that there aren't any cattle ranches up stream. But other than that, mountain water is pretty safe for backpackers. (My wife is a doctor and wants me to remind you how easy it is to purify your water anyway.) –  theJollySin Jan 9 at 16:21
If in doubt, filter it. Having the runs isn't fun and can be very dangerous especially if you are caught out in the wilderness. We do a fair bit of travelling and because of this invested in a SteriPen and haven't looked back. We still follow all the basic rules mentioned above but this removes the doubt. Have used it on hikes and ski tours around Sth America, NZ, UK, France, India and no stomach issues. A great wee device if you are out and about. Been hit by giardia once too often. BTW: We are no way affiliated with the brand or company just sharing our thoughts on an awesome bit of kit. –  SkiSchoolApp.com Jan 13 at 12:27

2 Answers 2

up vote 5 down vote accepted

I think your assumptions are correct. To my knowledge in a mountain environment you are quite safe as long as you follow some simple rules, which you mostly already named:

  1. The water was not standing, i.e.

    • it comes from a stream that is rather fast and
    • the stream is big enough that it is not just a connection of puddles or ponds where the water rinses from one to the other.
  2. There are no sources of contamination upstream. As you mention, thinkable sources are

    • agricultural areas where fertilizers or herbicides could have been used
    • meadows, where cattle was present
    • mining
    • (quite unlikely) the water runs through some geologic formation where harmful stuff gets washed out.

As long as you have checked such stuff, you should be quite safe with flowing water in mountain areas. Even the streams of melting water that build up on the surface of glaciers on summer afternoons will be rather fine then.

share|improve this answer
thanks, well that validates my assumptions. I think I'll leave off marking this as the answer, just to gauge a bit of opinion. –  Liam Jan 9 at 10:39

The bottom line is there is always SOME risk. Whether to take that risk or not is your choice.

Fast running + isolated + high elevation = prettttty low risk.

With that said the biggest concern is, unless you are drinking right from the source, you have no idea what has happened upstream from you. There could be a dead animal snagged in the stream, animal and human feces etc...

I have drank from mountain streams and not gotten sick, but I have seen others partake and get real sick...The choice is yours.

share|improve this answer
I do think the animal feces thing is always a bit overplayed. If there is 100,000 gallons going down this stream in x amount of time, it's going to take a hell of a lot of animal faces to pollute a stream. Dead animal maybe, but again the shear amount of water means (to my mind anyway) it'll have to be a pretty big dead animal pretty close to where your drinking to introduce enough bacteria to make you sick. –  Liam Jan 9 at 17:18
@Liam I do agree with you, I just wanted to point out that there still is a risk, how big of a risk is up to the individual to assess and use good judgement to decide how to proceed. –  AM_Hawk Jan 9 at 17:25

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.