>>2611496Depends. If I am somewhere with a lot of natural springs, I may not take anything. Never had any issues with that.
Other than that just think logically about the probability of a particular pollutant being there.
Is it a longer way down from the spring? That increases the chance of bacteria from dead animals, or animal feces near or in the stream.
Is there civilization upstream and do you live in a place where people are disgusting and use the stream of water for human feces? Expect viruses then.
Are there industry or chemical pollutants upstream and do you live in a country where companies don't have to (or choose not to) filter those out? Then chemicals are the issue.
If you have a lot of time, then boiling is great. Kills bacteria, kills viruses. Only chemicals stay an issue (which are hard to filter out in a reasonable timeframe, activated charcoal isn't enough most of the time).
I use a katadyn befree myself. Sawyer mini or Sawyer squeeze would be basically equally as good. The befree has more flow rate and is much easier to clean, but doesn't last nearly as long as a sawyer. I use a cotton bandana to filter any bigger dirt and particles as to not clog up the filter first, then filter through the befree. That removes bacteria and those are my main concern. Where I hike I rarely get water from bigger streams, so the distance from me to the spring is often minimal (or zero), so bacteria is the only realistic concern. If it's straight from the stream I wouldn't even need to filter but with how fast the befree flows I don't mind doing it anyways.
UV steripens are a solid choice for virus and bacteria issues if you have clear water, but I won't get another tool if there are no risk factors for it where I live.
