Water purificationn below freezing?

Steripen. I’ve used one year-round for about 4 years now.

I love my steripen in winter.

Steripen with lithium batteries (or built-in lithium rechargeables) says an Alaskan with 20 inches of snow still on my lawn.

And some extra fuel and more tea bags and hot chocolate mix.  And maybe an HX pot for a larger group trips.  You have to pack something for dinner – it might as well include more soup (as long as you bump up your fuel allowance).

And be aware of how VERY long chemical purification takes near freezing.  Varies a bit by chemical and dosage, but it’s NOT 10-20 minutes.  45-60-90 minutes of contact time means lots of pound-miles carrying the dosed water.  That’s fine for overnight, but while on the trail, zap it with UV and drink it immediately

A different question but along the same topic – how does one practically use a hollow fiber filter in freezing conditions? Is it not a thing? I suppose precautions could be taken to keep the filter from freezing? Backflush with rubbing alcohol to prevent freezing? Dry it out somehow?

“how does one practically use a hollow fiber filter in freezing conditions?”

Same as my friend who brought her infant along while following her husband along the Iditarod dog-mushing race.

You can’t leave it (the filter or the baby) anywhere it will freeze.  So you keep it inside your parka, sleeping bag, etc.

Back in the day, mushers had to do the same thing with alkaline batteries for their headlamps – a battery pack on a cord was kept inside their parka – a problem that lithium batteries mostly eliminates.

Rubbing alcohol?  I’d only backflush with rum or vodka in mildly cold conditions and Everclear in harsh conditions since I’ll be drinking water out of it later.  Then I’d drink that shot (can’t waste those calories!).

Or reuse the same 190-proof everclear to winterize the filter, recapturing it each time and then drink or burn it in your stove on the last day.

Although isopropyl alcohol isn’t especially toxic – a potentially lethal dose (with no supportive care) is around a pint.

I would not bother with the filter in winter conditions..  Steripen all the way, no contest.  I found when I started using a steripen about 4 or 5 years ago, I have not looked back. I have grown so fond of it that I am seriously considering using it year round.. though I do like my Be Free ….. when it works (SMH)… just DEFINITELY NOT in Winter.

My water filter never freezes in winter because it is at home in the garage.  I have always melted snow after the H2O I carry in runs out.  I don’t boil it if I am not cooking, but rather just drink the melted snow.  I have never been sick from that process that I know of.  But I have only been doing that for 50 years.

My friends said that if I bought a filter I would never get sick from giardia and they were correct.

how does one practically use a hollow fiber filter in freezing conditions?
It’s difficult. You need an awful lot of force to push the ice through the tubes.

As others have suggested: I sometimes (very occasionally) use a Steripen, but in the snow I never bother. I just make sure I am getting water (or snow) from a reasonable place. Melt-water is suitable.

Cheers

BUT – What about yellow snow?

A less interesting scenario – a trip where freezing temps are expected, but there is no snow to melt. I’m thinking arid portions of our country which might have non-frozen streams (which, so far no issues for hollow fiber), but then you have to take care about your filter freezing overnight. I suspect you just put the filter in a sealed plastic bag and sleep with it to keep it warm overnight.

In that situation, I’d still use a Steripen.

Ok, so all the options stated so far –

1) Use Steripen
2) Use hollow fiber filter, but keep it from freezing by keeping close to body when not in use
3) Don’t filter, snow isn’t likely to contain contamination
4) Chemical treatment as last resort

Anything else people are doing? For me, I think I’ll opt to keep my existing system (Sawyer) from freezing since I don’t want to spend an additional $70 for another filtration system I’m unlikely to use the rest of the year. Maybe the OPs funds are not yet spent, and so a Steripen may be a good solution for him year round.