A filter bag and a small bottle of treatment drops beside a silty creek

Guide · Water

How to treat backcountry water

Updated October 5, 2026

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In typical North American mountains, filter for bacteria and protozoa and carry chemicals as backup. Where viruses are a real risk, do not rely on a hollow-fiber squeeze filter alone. Keep dirty and clean containers separate. Do not let a filter freeze.

Know the threat

Giardia and bacteria are the usual backcountry worries at home. Viruses matter more with human contamination and in parts of the world with different water. A product that says filter is not the same as a product that says purifier. Read the claim.

A method you will actually do

The best system is the one you use when you are tired. A filter you understand beats a purifier you left at home because it was fiddly. Tablets are slow and reliable. UV pens need clear water and batteries. Silt defeats all of them until you let the dirt settle.

At camp

Collect enough for dinner and the morning so you are not filtering in the dark. Label the dirty bag. Do not dip a clean bottle into the lake to 'just top it off.' That is how the system fails after you did everything else right.

Gear for this guide

A squeeze filter on a soft water bag beside a stream

WaterSawyer SqueezeEveryday backcountry bacteria and protozoaHollow fiber · Light · BudgetOn Amazon

A soft flask with a filter cap beside a stream

WaterKatadyn BeFreeFast filtering from a soft flaskHollow fiber flask · Light · Budget to midOn Amazon

A bottle-cap water filter beside a stream

WaterPlatypus QuickDrawPeople who want a Squeeze-style filter with a better capHollow fiber · Light · Lower midOn Amazon

FAQ

Is boiling enough?

Yes. A rolling boil is the old reliable. It uses fuel and does not leave you with cold water.

Do I treat spring water?

If you did not see it leave the ground and the area has stock or people, treat it.