when/why does freezing damage water filters

Questions about equipment and supplies to bring on a trip (including reviews).

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torpified
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when/why does freezing damage water filters

Post by torpified » Sun Dec 10, 2017 7:31 am

This was prompted by watching UPS people leave packages on people's freezing cold front steps yesterday morning. I'm guessing cargo holds are cold too.

The kind of water filter, like the sawyer squeeze, you're not supposed to let freeze -- does freezing during shipment damage it? Or does the damage happen only if there's residual water in the filter that breaks up the internal structure of the filter when it freezes and expands? (In which case the dry filters being shipped are OK?)

Inquiring minds want to know. (Warning: if this gets answered, I also have questions about how a device could possibly simultaneously be an altimeter, a barometer, and thermometer. I remember just enough high school chemistry to constantly be perplexed by backpacking gear . . . )

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thesneakymonkey
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Re: when/why does freezing damage water filters

Post by thesneakymonkey » Sun Dec 10, 2017 8:48 am

If water gets into the pores of the filter and freezes it could expand the pores and allow larger particles to pass through "unfiltered".

I also pulled this directly from the sawyer website: (this is the filter I use so I am referencing this)

"Before initial wetting
Filter is safe from freezing temperatures if it has never been wetted.

After initial wetting
While there is no definitive way to tell if a filter has been damaged due to freezing, Sawyer recommends replacing your filter if you suspect that it has been frozen.

During trips
If you are in freezing temperatures, we recommend that you store your filter in your pocket or close to your person so that your body heat can prevent freezing. THERE IS NO WARRANTY FOR A FROZEN FILTER."
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Tom
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Re: when/why does freezing damage water filters

Post by Tom » Sun Dec 10, 2017 9:33 am

torpified wrote:
Sun Dec 10, 2017 7:31 am
(Warning: if this gets answered, I also have questions about how a device could possibly simultaneously be an altimeter, a barometer, and thermometer. I remember just enough high school chemistry to constantly be perplexed by backpacking gear . . . )
Thesneakymonkey correctly answered why many water filters cannot tolerate freezing. Note: There are some filters of different designs that can tolerate low temps/freezing, so read your manual accordingly.

As for your followup question that will come at any moment :D : Altimeters (aka Pressure altimeter) and barometers are essentially the same thing, mechanically. They would have different scales/calibration, but they work on the same premise of air pressure. If you stayed in one place/altitude, you will notice a pressure altimeter fluctuating, as well, as weather systems move through. It's also why pilots (at least in the era before radar altimeters) need to calibrate their altimeter to the local barometric pressure before landing, lest they smack into the ground sooner than they thought it should be there.

Thermometers work on a different concept, but the short answer for us backpackers is that in our modern world you can pick up an electronic chip that measures both pressure and temperature for less than $10. Many modern phones already have those incorporated, btw. That's how it's so easy to add them to electronic devices these days.


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Re: when/why does freezing damage water filters

Post by torpified » Mon Dec 11, 2017 7:29 am

Thanks for the pore report! I now feel better about the filter I got last Xmas (and slept with on IR in May). As for other matters:
As for your followup question that will come at any moment :D : Altimeters (aka Pressure altimeter) and barometers are essentially the same thing, mechanically. They would have different scales/calibration, but they work on the same premise of air pressure. If you stayed in one place/altitude, you will notice a pressure altimeter fluctuating, as well, as weather systems move through. It's also why pilots (at least in the era before radar altimeters) need to calibrate their altimeter to the local barometric pressure before landing, lest they smack into the ground sooner than they thought it should be there.
That makes sense, but it's also what confuses me. If altimeters just are barometers with good PR, how does my weather-predicting altitude-gauging ABC watch know whether to classify a change in what the altimeter/barometer registers as a change in atmospheric pressure rather than as a change in altitude? (Part of my original question was: or, given the ideal gas law, as a change in temperature --- but if temperature's measured independently, I guess that's not an issue?) Do the watches come pre-loaded with models that govern how they assign blame for pressure changes?

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