Isn't boiling the best way to purify water?

A: Yes, boiling certainly is effective at killing bacteria and viruses. You really don't even have to boil water for ten minutes—or four or five, for that matter. In practical terms, bringing water to a boil and holding that for less than a minute effectively kills just about anything alive in there.

So why are filters so popular? Lots of reasons. For one, they allow you to fill up with water while on the go, hiking or biking. No stopping, setting up a stove, and boiling a quart so you can have something to drink. For another, you boil water and you have... hot water. Great for coffee, not so great for a cool drink on a hot summer day. Boiling also means you must have a stove, and maybe you're just day hiking and don't want to hassle with that.

Meanwhile, filters also do something that boiling cannot: They remove many waterborne chemicals and even filter out "off" tastes.

So there you go. I boil water as a means to purification when the boiling has another purpose—making dinner, or brewing coffee. Otherwise I use a filter. To some degree, which filter is a matter of preference, but I've long used—and liked—the MSR MiniWorks, now in an improved design called the MiniWorks EX ($80; www.msrcorp.com). Sturdy, easy to use, effective—at least, I haven't contracted anything after using it!

Check out Outside's 2004 Buyer's Guide for more on water filtration and purification.