UKH

While being out in the mountains and remote areas, I have always been drinking directly from streams for last decade or so and haven’t had a problem. However, some of the trail runs are more civilised (especially these times!), at lower levels and I would rather not rely on carrying water. Sometimes, streams near bothies weren’t convincing either (thinking of Mark Cottage...). 
 

I had my eyes on MSR Trailshot - is it any good for use in Scotland, when being at 0-400m altitude and, more importantly, near farmlands and civilisation? It sounds like a nobrainer at 150g as that’s merely a cup of water. 

Also, how bad does it taste? Is loch water any good? 

 I have a trailshot and I like it. Tastes a little of plastic but way better than chlorine tabs! Used it in the Peak, lakes and scotland, sometimes near to civilization. I haven't got sick for what it's worth. 

As you say they are really light and I think they are easier to use and more versatile than the squeeze ones like Sawyer.

Have you tried the Katadyn BeFree, I think it's really easy and quicker, basically a normal water bottle. I had the mini Sawyer one but eventually burst the bag. Using those I've drunk from any standing water. TBH the biggest issue is warm water, it just never tastes good.

It's been reviewed twice here, on its own by Dan I think then as part of the hanging bag system by me. 

Be aware that near farms or industry there is a potential for stuff in the water that no filter or purifier can remove. At lest that's what I took from researching it.

I've happily used a trailshot for a few years now in the UK and Europe. 

No idea if me not getting ill is down to its efficiency or if it's a placebo.

What I have noticed is that the flow rate rapidly drops from new and now (despite doing the cleaning ritual) using it is a good forearm strength test.

Also I need to prime the filter to get rid of air, otherwise filtering takes forever.

What I forgot to also say is that I love the pre filter - I find I regularly have to clean it but it saves all sorts of debris reaching the main filter.

I carry a Sawyer Mini in summer and it's pretty versatile. Handy for ridge walks especially, it can be used like a straw or wih a roll up 'dirty' bottle to squeeze thro. Thread fits most PET pop bottles too. It ca.n also be fixed inline on  a bladder tube. I went for it initially as it had the smallest physical filter size at 0.1microns.

Can be a bit slow to squeeze or hard to suck depending on water quality and you cant use it below zero C (freezing will damage it by bursting the micro tubes). But easy to backwash between trips (syringe supplied) and no throughput or time limits (being a physical filter).

Current price about £25 (£17 three years ago).

I haven't as I saw it after I bought my trailshot and couldn't justify owning 2 filters! It looks really cool though, I'd consider getting one if I ever actually get into hell running? Would you recommend it then?

I bought a trailshot in the Pyrenees last year. I've never filtered water in the mountains of Europe before and didn't realise how high up the mountains animals grazed there so thought some purification would be sensible.

On one wild camp we couldn't find any water anywhere except a cattle trough which as well as having been drunk out of by cows, had algae floating about in it. We filtered that and didn't get ill.

I found it light and very easy to use and subsequently read some very good reviews of it.

I like it, as I do lots of longer days out in the mountains but in areas with tourists. In the UK I'd generally just drink from streams but these streams are a bit riskier. Supposedly it filters enough to remove the risk and so far no issues, it's very fast and easy.

The Sawyer was good for the size but it was slow and on FKT runs I was squeezing it to speed up and it eventually burst on me. I gave it some pretty heavy use though.

I've always drank from stream as well and avoided still bodies of water but interestingly I listened to a podcast from a wildness medic who suggested the opposite. Apparently the movement of streams kicks up more sediment and bacteria whereas in a lake all the sediment will sink. The sunlight should also sterilise the top layer of water much like a UV filter would! 

That's interesting! I've always done the same as you since that's been the received wisdom. 

I'd echo what Toby said - be careful in the vicinity of farms and industry (to which I'd also add main roads), which basically equates to most lowland settings in the UK. I'm not convinced any commercial 'outdoors' filter is worth risking when it comes to hardcore pollution.

I tend not to bother filtering burn water when up high in the Scottish hills, but would do so if it's from a skanky pool or bog, or downstream of a popular trail or bothy. In England and Wales the pressure of walking numbers (and their waste) and the density of sheep make filtering seem sensible a lot more of the time.

Modern compact filters are really convenient, minimal faff and well worth the weight.

Here's a review of the Katadyn BeFree: https://www.ukhillwalking.com/gear/camping/water_treatment+flasks+hydration...) 

We also got on well with the MSR Trail Shot: https://www.ukhillwalking.com/gear/camping/water_treatment+flasks+hydration... 

Thanks everyone, Trailshot it is. 

Knowing how awful food poisoning can be, I’d rather not risk with anything like that while on the hills. I genuinely thought I’m going to die, and NHS was “just take some paracetamol, you’ll be fine in some hours”. They were correct. 

If it removes parasites, bacteria and viruses, what might it leave in? 

Dissolved chemicals, nitrates, pesticides etc.

I think heavy metals are also a problem in some places, not sure where though

What Basemetal said, all those nasty "chemicals" (I know cow poo is made up of chemicals as well, so that why I avoided saying "chemicals" in my first post).

BTW I don't think the Trail Shot can filter out viruses. IIRC that's the difference between a "filter" and a "purifier" like https://www.ukclimbing.com/gear/camping/water_treatment+flasks+hydration/gu... but even that can't take pesticides out and similar. Again - no expertise on this - just what I tried to understand when writing the reviews, most aided by a friend who is an Assistant Professor in Bio-sciences!

So would it be right to say a purifier removes 'life' as in organic material, bacteria, parasites etc - but these filters are limited in removing substances at the molecular level which is why soluble chemicals pass through?

I honestly don't know but it must be something like that.

It's not been mentioned but I really rate the Platypus GravityWorks. Used it on the Appalachian trail, Pennine Way, Welsh 3000s, and loads of other weekenders. 

Filters catch the lumps and let the liquid through.  Bacteria are lumps and can be removed if the filter is fine enough.  The UV pens, chlorine tabs, and boiling strategies to treatment aim to leave the bacteria in, just kill it.  As others mention above, the filter wont remove anything that is dissolved in the water like heavy metals or other nasty chemicals so even with the worlds best filter you have to be picky about the water source.  The same is true in water treatment for public supply.  Some source water might just be too high in lead, iron, manganese, bromates, nitrates to be worth bothering with because it starts needing expensive processes to remove or another source to blend out.  I'm not adverse to drinkingwhats about me on the fells, but the lower down the watercourse I am, the more likely I am to filter, chlorinate, or just carry extra.  If theres a mine working, agriculture, or a house upstream I strongly consider how thirsty I am.

I bought a lifestraw a few years ago.  Useless if you want to process a whole bottefull (I use chlorine tabs for that) but good for taking a quick drink because of the low faff factor. Pop the cap off and suck your drink through it.  Can feel like you're trying to suck a golf ball through a garden hose but dont need to set up a gravity or pump arrangement, and can even do away with a bottle if you dont mind doing a press up over whatever you're drinking from.

Thanks, good advise. 

I get the harm of the bacteria, but what are the viruses we are talking about (for once, it's not COVID-19, right?)? Are any metals dangerous if you drink just enough to find a better water source (let's say, a campsite at most)? 

I am not planning to go and drink water from River Clyde any time soon, but I wonder, how much does the filter actually help then? If we had three water sources:

• Happy to drink from without a filter; it's a high flow stream in remote area with no animals around and at a higher altitude.
• Would rather avoid unless necessary; either some animals are roaming around, it's not so high up the hills OR it's closer to civilisation.
• Would not drink; it's in a city, right by a farm or road, etc. 

Where does the filter fit in? Is it the second category, where you are having doubts? 

I don't tend to drink that much - had a self-supported 50K with 1L of water that was done in just over 5 hours, but it's getting warmer again. I'm not planning to do any runs with just filter and no bottles. 

My understanding is that whilst viruses are much smaller than bacteria, viruses often use bacteria for a host. At least this is how my friend who has relevant scientific knowledge explain it to me. So purifiers like the MSR guardian can catch viruses on their own, but my friend at least thought that actually a filter that will filter size of bacteria will also catch many viruses. 

I've noticed that filtering peaty yellow water through the guardian results in peaty yellow water coming out. I guess this shows that the coloration may be coming from chemicals that are dissolved in water, rather than anything in suspension. So I presume the same might be true with potential industrial chemical pollution.

Yeah my personal approach would be to use it in that second category, where I might also be considering tablets, but the advantage of the filter is you dont have to wait half an hour and it doesn't alter the taste.  A filter can also improve the effectiveness of chlorine or uv- they can be overloaded by dirt, so filtering out the solid particles making the water cloudy then zapping any bugs that may have made it though the filter's sieve.

As for specific viruses I dont know what we are at risk from. I know cryptosporidium and e.coli can be risk factors with animal poop about.  Gardiara maybe? I'm not hot on biology, but my understanding is that viruses, although small, still have a lot of atoms in them so are a bigger lump than dissolved chemical ions, so can be filtered out with a small enough membrane.

To be honest my filter doesn't see that much use. My partner and I did the arctic circle trail and boiled water at most, often just drank it from the lake or stream.  We backpacked across the Lakes drinking some bog water on occasion and just ran it through a cloth then chlorinated. I did use it on a Yorkshire three peaks where I was 2/3 way through during a heatwave where I'd grossly misunderestimated how much water to take and sipped from the least sheepy looking stream I could find.  Adding to your first category, I believe that if it's shallow water in bright sunlight, its getting a natural UV dose from the sun, and if it's cascading the dissolved oxygen can also help to treat any bugs.

Cheers. Been reading up a bit and it looks like viruses that are dangerous to certain species are also transmitted from the same species. I.e. human poo makes it more risky than animals roaming in the area. 
 

Given I had week long trips in Scotland where I didn’t filter water, a small water filter won’t hurt. I vividly remember a day in Cairngorms where I spilled the tea in the morning and completely run out of water by early noon. It was a hot summer day - I sunburnt twice over 9 days of that grand traverse and the water sources were all dry. I met few folk who pointed me to a stream and I didn’t think twice about drinking from it. They also gave me a bottle of water which I just downed immediately as I haven’t had between 4~5 Munro tops. I did pass few puddles, but they didn’t look appealing. 

Yeah I thought that was how it works with the species thing, I just couldnt get the idea together into a sentence.

For what it's worth most water treatment plants (in my part of the UK anyway) have at least a filtration and a chlorination stage. The filter does most of the legwork but the residual chlorine helps to keep the network clean and makes sure any bugs that make it through the filter cant multiply back up the the original levels. Might be too much faff for a run but worth keeping in mind for your longer trips or more unappealing puddles.

TobyA mentioned colour, that's achieved in industry by adding a flocculant, which causes the charged chemical particles causing the colour to clump together for removal.