What is the best way to purify water while backpacking?
Filters and Chemical Treatments
Pump filters, squeeze filters (like Sawyer or Katadyn BeFree), and gravity filters remove bacteria and protozoa like Giardia and Cryptosporidium. Most do not remove viruses, which are less common in North American backcountry but present in some developing countries. Filters are fast and don't leave a taste.
Chemical treatments (chlorine dioxide tablets or drops) kill bacteria, viruses, and protozoa, but take 15 minutes to 4 hours depending on the product and water temperature. They're lightweight and good as a backup. Some people dislike the slight chemical taste.
- Filters: good for sediment removal; not for viruses.
- Chlorine dioxide: effective against viruses; needs wait time.
- UV light (e.g., SteriPen): fast, but needs clear water and batteries.
- Boiling: kills everything; requires fuel and time to cool.
Choosing and Combining Methods
For most U.S. backpacking, a squeeze filter is a popular choice because it's light, fast, and easy. If you're hiking in areas with viral risk (e.g., some international destinations), use a filter followed by chemical treatment, or choose a purifier that removes viruses.
Always have a backup method in case your primary fails—a filter can clog or break. Chemical tablets are light and reliable. Pre-filter cloudy water through a bandana to improve effectiveness and taste.
- Carry a primary method and a backup.
- Pre-filter murky water to extend filter life.
- Follow contact time instructions for chemicals.
- Boiling is the most reliable but least convenient.
Common mistakes
- Assuming all filters remove viruses—most do not.
- Not waiting long enough for chemical treatments to work.
- Drinking untreated water from a pristine-looking stream, which can still contain pathogens.
