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How to Filter or Purify Water in Freezing Temperatures

Water filtration and water purification are as important in freezing weather as they are the rest of the year. Giardia, bacteria, and cysts don’t go to sleep when temperatures dip near or below freezing, nor do beavers, mice, deer, rabbits, and all the other animals of the forest that can contaminate the water supply with organisms that cause water-borne illnesses in humans. The only thing that does change is the effectiveness and convenience of different water treatments and purification methods.

What are the pros and cons of the water filtering or water purification techniques that backpackers normally use in warm weather, when temperatures get frosty and dip below freezing?

  • Water filters that use hollow tub filtration technology like the Sawyer Squeeze, the Katadyn BeFree, Platypus Gravity Works, and others break when they thaw after being frozen, even if only partially frozen. Once this happens, there’s no way to know or test whether they’re still effective or whether they’ve been compromised.
  • A pump filter like the MSR Guardian ($350) can withstand a limited amount of freezing/thawing and is a good option if you afford it. But other pump filters like the Katadyn Hiker Pro or the MSR Miniworks are ruined if they freeze.
  • Ultraviolet purifiers like the Steripen can fail if their batteries freeze or lose power in cold temperatures. While lithium-ion batteries won’t freeze like alkaline batteries, their discharge rates can drop too low for cold-weather operation.
  • Liquid chemical purification drops like Aquamira or liquid bleach can freeze and become useless.
  • The reaction time of chemical purification tablets like Katadyn Micropur, AquaTabs, or Potable Aqua slows down in cold water, although they are not prone to freeze-thaw issues like their liquid counterparts.

Philip Werner gives a complete explanation on how to filter or purify water while in freezing temperatures, you can find the complete article here


May 7, 2022

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Section Hiker

Media Mentions from Section Hiker

Philip Werner is a full-time outdoor author and backpacker who resides in New England. His website is ranked as the #1 Hiking and Backpacking Blog on the internet by in 2018, 2019, 2020, and 2021.

The name of this site, Section Hiker, refers to the Long Trail which I section hiked in 2008 and the Applachian Trail that I’m still working through. To date, I’ve completed 1400 miles of the AT and hope to complete all of the sections between Georgia and Maine someday. I’ve also hiked thru-hiked the TGO Challenge (Coast-to-Coast across Scotland) twice and I’m currently section hiking the Cape Wrath Trail, also in Scotland.


My only complaint is that eventually, backflushing won’t be enough. These can clog up after some time and no amount of back flushing will fix its low flow. I went through 2 on the AT. However, it will attach to Smart Water Bottles and most bladders!

Anna Hamrick


Built for backcountry reliability and portability, the Sawyer Squeeze filter is our pick for the best portable water purifier.

Pete Ortiz


The Sawyer Squeeze was (by far) the most common Pacific Crest Trail water filter this year – for the fifth year in a row. It’s a $39, 3 oz / 85 g hollow fiber filter that rids your drinking water of protozoa and bacteria (and floaties). It can be used with Sawyer bags (included with the filter) or with compatible water bottles (Smartwater is the bottle of choice for many hikers).

Halfway Anywhere
Media Mentions from Halfway Anywhere