UKC

I've always avoided standing water in the hills for obvious reasons.

However, the other day I was walking near some high up tarns around Ben Alder and I wondered how dangerous it really is. I'd never drink it neat, but scientifically, is it safe to drink after boiling, a purification tab, or both?

I've heard that bacteria begin to die after 60C and it's unlikely there will be excess amounts of heavy metals that high up.

Does anyone have any scientifically-backed up facts on this? Or does anyone regularly drink boiled or purified tarn water?

I regularly drink untreated from streams and cleaner looking lochs. Never had a problem in 40 years.

Only ever drunk from streams waterfalls, and melted snow myself.  Simplest way to be safe is to filter. I keep thinking I should get one.  Others I walk with drink safely from what are basically muddy puddles using a filter.

Likewise (although getting on for nearer 50 years). The obsession with filters and treatment has always seemed a bit OTT to me. Only abroad have I treated water (iodine) and didn't have any problems. If you drink from a stream below a popular camping spot then that wouldn't be sensible.

why WOULDN'T you drink it if boiled/filtered? you could drink out of a toilet if you Boiled it thoroughly enough!

sounds like you have an overly cautious approach, if its clear, fresh and flowing then its probably fine, if it tastes/smells a bit funny them obvoiusly stop! otherwise, enjoy! standing water, i wouldnt drink out of a small puddle, but a sizeable lochain/tarn well away from human activity is probably as fresh as you can get!

What about blue/green algae?  There seems to be a problem with it this year.

https://www.argyll-bute.gov.uk/news/2021/jun/check-blue-green-algae-if-near...

I've been drinking from upland tarns and streams for over 50 years.  

Its probably better filtered than the water you get from the tap, which in most treatment plants consists of little more than the addition and later removal of flock to remove solids, treatment with chlorine to remove bacteria and so on.  It is not boiled of course. 

A hillside covered in largely mineral soil and vegetation  makes a lovely filter.  That combined with exposure to UV radiation makes pretty safe water I'd say.

i would imagine that is mostly a low elevation issue but happy to be corrected. but either way, if there is an alagl bloom then the water is going to look cloudy, and would probably taste funky too!

Dunsapie Loch in Edniburgh is only collecting water which has run off Arthur's Seat but it quite often has algal bloom in summer.

Right now there are warning signs and the water is obviously cloudy.  The problem case would be when the problem is not severe enough to be obvious but severe enough to do you no good if you drank the water.

I drank some stream water or Helvellen once and it tasted Devine.

I then got Guardia Lamblis and spent 4 years under the consultant while my digestive system recovered from that little protozoa.

Didn't stop me drinking fresh stream water though.😀

In the US the CDC publish a guide to drinking non potable water (i.e. how to make it safe)

https://www.cdc.gov/healthywater/emergency/making-water-safe.html

They advise rolling boil for 1 minute ( or 3 if above 6,500ft).

As someone else who has giardia, it definitely doesn't feel OTT!

I carry one of the little msr filters these days. Always seems worth it. 

When I was up at Red Tarn recently I boiled water then filtered it cool.  So hopefully anything being filtered was dead whether or not it went through.

As I swam for an hour I suppose that was a waste of time though I tried not to swallow the water.  I went a long way from the outlet and as far from other people as possible.

"Only collecting water which has run off Arthur's Seat."

There is a road, car park and an incredibly high foot fall compared to upland tarns which have no cars driving past them.

If you are needing to get a drink from Dunsapie Loch you should probably be having words with yourself.

Filters are pretty inexpensive these days. The 'Water to go' bottles seem to do a good job for about £15, or the Sawyer filter that can attach to a standard water bladder are my go-to. Years ago, when I was fitter, I did a few mountain marathons in Scotland and regularly drank from free running burns, but it always felt a bit risky. 

Water-to-go bottle is what I use too, they filter chemicals which is the reason I chose it over more popular ones. The places I walk have a lot of old silver and lead mines which are still polluting the local watercourses.

My sympathy - perhaps you've been unlucky? After decades of swilling water from becks, brooks, rivers, allts and afons I've had no problems. I think it boils (no pun intended!) down to being careful about where I consume. I'd be fine about a remote source in the high North Pennines, far more cagey about one next to a busy Lakeland path. Mostly, these days, I do carry up to a litre of the council's finest filtered and treated to the highest standards. One story I heard in the States about giardia was that it was introduced into many back country streams by returning Vietnam troops. True or not, I treated water with iodine drops and had no trouble.

A fine tale regarding the Vietnam connection but unlikely. Widespread through various animals in the US, beavers are a major source of Giardia cysts. More prevalent in north American beavers than Eurasian beavers. There have been trials in at least some of the beaver reintroduction projects (hopefully all, but I only know for certain in some) in the UK to monitor any resulting effect on the presence of Giardia.

There is a road and a car park but the road is usually shut to vehicles since Covid.   The point is the water in the loch has run straight off the hill, there's no agriculture or anything like that putting nitrogen in it.  People walking past isn't putting nutrients in the water which cause algae to grow, and as the link I posted earlier shows there are similar problems in lochs in the highlands.   Last year there were otters in the loch, this year I think they've gone.  From what I read the algae is worse this year because of the hot weather.