Die, Bugs, Die!

Sure, a pump filter will remove harmful microorganisms from water. But you still need a viricide—think chlorine bleach, chlorine dioxide, or iodine—to finish off the really small, really nasty stuff like Norwalk, the curse of cruise lines everywhere. All these chemicals work, but some are less effective in very cold or murky water. And remember: Viricides are poison; read and memorize the instructions. A recent addition to this list is ultraviolet light. It kills everything, and you can't beat the push-button convenience.

2004 Buyer's Guide: Bugs

Iodine Tablets
SUCH AS: Potable Aqua ($6 for 50 tablets)
COOL: Two tiny tabs in a quart kills bacteria, giardia, and viruses.
NOT SO COOL: Ineffective against cryptosporidia. Have to wait 30 minutes. Brief shelf life (up to one year) once opened. Not for prolonged use (more than six weeks) or for anyone with thyroid problems. Treats only 25 quarts. Hint: Buy a combo package of Potable Aqua with PA Plus ($9). Add the Plus (ascorbic acid) after 30 minutes to neutralize the strong iodine taste.

SUCH AS: SweetWater Purifier Solution ($9), household bleach
COOL: Five drops in a quart of water kills viruses within five minutes.
NOT SO COOL: Brief shelf life—only a few months for bleach. Makes water taste like wash day. No good against crypto, and SweetWater makes no claims about bacteria.

Iodine Crystals
SUCH AS: Polar Pure ($10)
COOL: Adding water to crystals in dispenser bottle creates iodine solution that can disinfect 500 gallons of water.
NOT SO COOL: Same as iodine tablets, except shelf life is unlimited—as long as you don't break the bottle.

Chlorine Dioxide
SUCH AS: Katadyn Micropur MP 1 ($14), Pristine ($14), Aqua Mira ($13)
COOL: The only chemical treatment that kills all the culprits: bacteria, viruses, and those notoriously hard-shelled critters, cryptosporidia. Micropur tablets are EPA-certified and easier to deal with than Pristine and Aqua Mira. Long shelf life (three years). No noticeable taste. No known negative health effects.
NOT SO COOL: Pristine and Aqua Mira require mixing of two liquids. Worst-case scenario (cold, turbid water) requires a four-hour wait to kill crypto.

Ultraviolet Light
SUCH AS: SteriPen ($149)
COOL: Ultraviolet light from a half-pound handheld gizmo takes just a few seconds to zap viruses, bacteria, and cysts in 16 ounces of water; two doses will disinfect 32 ounces. Just turn it on and stir. The newest version—expected in May—offers a rubberized handle for a watertight seal in the company's new Nalgene-compatible filter cap ($7).
NOT SO COOL: Needs batteries. Quartz tip and electronics require care to protect, although the company claims the new version is extremely rugged. Either way, the sturdy case is a big help here.

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