How To: Stop a Backpacking Water Filter From Freezing in Cold Weather


During the summer, water purification is fairly straightforward. If you have a water filter or purifier tablets you’re basically good to go. Once the weather turns, purifying water is a whole new ball game.

You not only have to deal with bacteria and protozoa, but you also have to battle your gear in the freezing temperatures. It’s hard to keep your water filter from freezing in cold weather.

Why I Use a Filter in The Winter

Even though a backpacking water filter isn’t the best winter purification method, it’s my first choice. When I first got serious about cold weather camping I asked a buddy how to keep my water filter from freezing.

His advice was to keep the water filter in your sock drawer at home… Obviously I ignored that advice and found a way to keep my filter from freezing. I’m not crazy, I always carry chemicals for backup.

Water filters are so much easier to use than purification tablets(instantly clean water). Purification tablets take a long time to work, 30-60 minutes in warm weather and longer throughout the winter. UV Filters are great in the cold, but batteries are unpredictable in cold weather.

If you don’t have purification chemicals you should definitely buy some(On Amazon). They’re so cheap and you should always carry a backup purification method.

Backpacking Water Filters aren’t The Best Winter Purification Method

Let me start off by saying that water filters aren’t the best purification method in winter. During the winter you’re better off using purification tablets(On Amazon) , UV Filters Like the Steripen Ultra(On Amazon), or just plain old boiling water.

These methods are more reliable, but keep in mind that it’s going to take longer to purify water. Even if you choose to use a water filter it’s always a good idea to have a backup purification method.

Melting Snow

If you melt snow for water, you really don’t need a separate water filter. Boiling water will provide all the purification you need. Just be careful not to burn a hole in the bottom of your pot. This is easier said than done if you don’t know what you’re doing.

It seems counter-intuitive, but you need about 1 cup of “Seed Water” to melt snow without burning your pot. If you add snow to your pot without seed water it’s going to burn a hole in the bottom of your pot.

Keep in mind that it takes a lot of snow to get a decent amount of water. Beginners quickly learn that liquid water is a valuable resource, and while you can get water out of the snow it’s easier said than done.

How to Prevent a Frozen Water Filter

So how can you stop your water filter from freezing in cold weather? A frozen backpacking water filter is bad news. Once your filter freezes it seizes up, cracks and loses its filtering ability.

You’ll not only be left without water, freezing usually destroys the filter. After a freeze, there’s just no way to tell if you’ve permanently damaged the water filter. Continue to use it and you run the risk of taking in bacteria(salmonella, cholera and E. coli) and protozoa(giardia and cryptosporidium). Hopefully you won’t get sick.

The Easiest Ways to Prevent a Freezing Water Filter

In sub-zero temperatures, there’s no way to guarantee your water filter won’t freeze. You’re just working against the laws of thermodynamics at that point.

That being said, if the temperature are in the low teens I’m a filter user. I always carry chemicals as backup, but I’ve never actually needed to use them. By following these methods you shouldn’t have to worry about a frozen water filter.

Keeping Your Backpacking Filter Warm During The Day(The Easy Way)

Let’s be real here for a minute. During the day you’re probably not worried about a frozen water filter. It’s gonna take seriously cold weather to freeze a water filter during the day.

Unless you’ve got serious gear/knowledge I would never recommend backpacking in this type of weather. It’s just not worth risking your life at this point. If the weather is like 10 degrees during the day it’s gonna be absolutely freezing at night(Good Luck).

That being said, you can easily prevent your water filter from freezing during the day. If you have a small water filter like the Sawyer Mini(On Amazon) which I highly recommend, just throw it in your pocket.

Your body heat should be able to keep the filter warm enough on most days. In seriously cold weather you might need to toss in a hand warmer(On Amazon) or two.

What About Extreme Cold?

If you’re dealing with extremely cold weather you might want to change the way you purify water. Your best bet is to boil snow, use a portable UV Filter like the Steripen Ultra(On Amazon), or purification tablets. Just keep in mind that it takes longer to purify water in cold weather.

Prevent a Frozen Water Filter at Night(Sleeping Bag Method)

At night there’s only one surefire way to keep your water filter from freezing. You need to use your body heat to keep the filter warm. This means tossing it into your sleeping bag.

If the filter freezes in your bag you have worse things to worry about than a frozen filter. Check out my post on freezing to death in your sleep.

Before throwing the filter at the foot of your sleeping bag you need to toss it in a Gallon-Sized Ziploc Freezer Bag. The plastic bag will stop the trapped water in your filter from leaking onto your sleeping bag. You’ll end up with condensation issues and nobody wants to wake up to a soaking wet bag.

What if My Camping Water Filter is Frozen?

If you can’t get water to flow freely through your filter it’s probably frozen. Hopefully, you have other purification methods, because freezing temperatures damage the structural integrity of a water filter.

There’s no way to tell if your filter is damaged beyond repair. As a general rule, if a water filter has been frozen solid it’s going to develop leaks in the filter element. You can usually get away with a slight freeze, but it’s better to just replace the filter. For the price of a sawyer filter(on amazon), it’s just not worth the risk.

If that’s the only water purification method you have I guess you’ll either have to risk it or boil some water. Always try to stop your filter from freezing before it can get damaged.

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