Waterborne Viruses/Filter limits/W.HighlandWay

[Falstaff]

FYI for all:
Unable to find the thread about water pollution on the West Highland Way. This is a good explanation/valid rant of the failure of most filters to protect, by someone who got sick despite being aware of the issues. (due to cross-contamination).

Whilst I was aware of the virus issues, and use a Grayl, I realised I'm not doing enough to prevent cross- contamination even with a Grayl.
My tentative solution for most filters is to use sandwich bags, to keep dirty water filter items separate from clean side stuff. ? (And/or puritabs).
That includes not dipping the Grayl container into a stream per their advertising!

I was thinking of bagging the Grayl inside a Milton bag (for prior filtering to extend the life of the filter), but now need a rethink on the whole using & carrying method. I do agree with him about the misleading advertising.

 

[hughtrimble]

FYI for all:
Unable to find the thread about water pollution on the West Highland Way.

Small thread about it here:

F

Post in thread 'Sick after drinking filtered river water'

May 22, 2026

Marketing and laziness/practicality!

I suppose the alternative to boiling might be the chlorine tabs, metabisulphate or even potasium permanganate ? Boiling say, 3ltrs a day, would use a lot of fuel. (and time)

Don't think it was the case here, but there are also individual's reactions to ingesting some things, irrespective of any bugs, virus etc.

• Falstaff

• 

 

[hughtrimble]

I too use a Grayl - must say I found it far from easy to use out in the sticks with the amount of pressure required to filter through it, even using visibly clear water running into the tarns in the Lake District. Definite habit of it spurting out upwards at my face if not completely aligned thus adding further to your contamination risk note.

I think next time I'll keep using it, but maybe take one of the hand pump filters as getting the Grayl receptacle into the water was pretty hairy sometimes.

Your idea of adding a Milton is interesting - we're both considering taking extra kit to do the job the Grayl is supposed to do! But the viral risk is going to impact the vast majority of trekking filters if used alone.

Makes me think I should just make the effort to coarse filter and boil/treat the water rather than using the fancy filtration gizmos in terms of safety and weight.

 

[Falstaff]

The Milton bag is a very old method that is fine for sediment and solids, but needs to be flushed out and dried. I'm going to try making one of the quick-dry double skin nylon ones Greencraft demonstrated.
However, it doesn't stop farming chemicals, even on the moors they use some stuff, that's where the Grayl comes in. Definitely a knack and go slow pressing it down.
I'm thinking of some form of receptacle on a line to chuck in and draw water, then pour it into the Milton and thence to the Grayl. Maybe even the Milton bag itself with something to hold it open, but I wouldn't want to snag and lose it. Cut open plastic cola bottle maybe?

 

[shaggystu]

Millbank bag not milton bag, sorry, it's bugging me. Milton make sterilising tablets for baby bottles.

 

[Falstaff]

Millbank bag not milton bag, sorry, it's bugging me. Milton make sterilising tablets for baby bottles.

Ha ! Thank you. It's crap getting old and reaching for a word but it won't come or, you know it's not quite right.
I notyice that I have to check some of my spelling sometyimes now for the same reason. (a joke, but true)

 

[shaggystu]

It's a perfectly understandable mistake, milton/millbank, both used for "cleaning" water... My brian aslo strugglez wiv spellink sumtymes, better old than the alternative though

 

[slowworm]

I like the idea of a Milton bag, made from brightly coloured shirt material with a good sense of humour.

 

[hughtrimble]

I like the idea of a Milton bag, made from brightly coloured shirt material with a good sense of humour.

My Milton bag runs circles around all other filter types.

Or is that my Keynes one...

And don't mention Maynard.

 

[shaggystu]

I like the idea of a Milton bag, made from brightly coloured shirt material with a good sense of humour.

I think if you're relying on an old t-shirt to filter your water then a sense of humour is more or less compulsory.

 

[GreyCat]

I recently bought a British Berkey gravity filter for the house.

They give very clear instructions about avoiding cross contamination of the clean water vessel, and that disinfection is also needed (if using it to clean e.g. stream water).

But there is a thing these days that folks rely on the magic gadget rather than thinking/understanding how it works and any limitations. Same thing as relying solely on their phone for navigation......

GC

 

[Danceswithhelicopters]

Grayl all the way. Efficient filter design with a level of filtration I'm happy to use as an alternative to a rolling boil. The chemical removal is a bonus.