Every ounce gets argued over on a long hike, and the water may be a shallow trickle between rocks. The criteria: weight per liter, packed size, drinking straight from the source, no batteries to fail, and scooping from an inch of water. Each item below qualifies on one or more of these counts.

Camp water comes from a lake or a spigot of unknown history, and a group drinks more than expected. What matters: batch volume for several people, gravity flow while you cook, tolerance for silt, field cleaning, and a build that takes knocks. The picks below each deliver on one or more of these fronts.

A boil-water notice or a broken main turns tap water into a question mark, usually with the power out too. Preparedness favors filtration that needs no electricity, a broad contaminant range, long cartridge life, years of shelf storage, and flow enough for a household. Every pick below meets at least one of these criteria.

Foreign tap water is unfamiliar rather than unsafe, and bottled water leaves a trail of plastic. Judge a travel purifier on carry-on packability, handling of unknown taps, taste and odor reduction, quick refills at a sink, and filtration inside the bottle. Each pick below earns its place through at least one of these strengths.