Do these pump-free water purifiers work?

I think it’s a great gadget. The MSR Miox ($130; www.msrcorp.com) is a brilliantly clever little device that uses salt and an electrical charge to create an extremely powerful germ- and virus-killer. You mix some untreated water with a dose of the salt, let the Miox charge that mixture with electricity, then add the result to your drinking water. Within 30 minutes it kills nearly all bacteria, protozoa such as Giardia, and viruses (cryptosporidia take longer to kill, about four hours).

As a bonus, the Miox is much smaller than a filter—about the size of a large whiteboard marker—and can treat water for an entire party.

There are a few minor downsides. It doesn’t filter water, so you’ll still have some grit, dead Giardia, and any aftertastes already in the water (the Miox solution itself is tasteless). It’s not a “drink now" method, so you can’t find a cool stream, filter a quart of water, and have a sociable drink. And it’s electrical, so there’s always the chance of a problem there, although its CR123 batteries last for some 200 recharges.

I wouldn’t necessarily say the Miox is perfect for everyone, but it sure is an excellent alternative to bulky filters (none of which remove viruses, anyway, so still require extra water treatment in many parts of the world).

Check out this year’s more than 400 must-have gear items, including a comprehensive hiking section, in the 2006 Buyer’s Guide.