But that's the ideal scenario. Once, deep in the North Dakota Badlands, I was forced to drink filtered water from a cattle trough. Then there was a time in Utah, hiking along a silt-choked tributary of the Green River, when my partners and I pre-filtered sediment through a pair of (clean) underwear stretched over the mouth of a bottle.
This summer I tried something different. Instead of underwear and pills, I hiked with a small ultraviolet light-emitting device that destroys the DNA of microorganisms, making them unable to reproduce and cause illness.
Seriously, the SteriPEN Adventurer zaps microbes, viruses and bacteria, including the well known likes of giardia and cryptosporidium--famous havoc-wreaking bugs that swim and swirl in tainted water unseen.
The device, a $129.95 product made by Hydro-Photon Inc. (www.steripen.com), is simple to use: Stick the pen in water; push the button to activate the UV light; stir the water until the indicator light turns green; remove, and drink.
It takes about 50 seconds to purify 16 fluid ounces, and about 90 seconds for a liter.
The SteriPEN is compact and durable, weighing in at 4 ounces. A hard plastic cap protects the light source when not in use. It runs on common CR123 batteries.
The company promises to protect its users from diarrhea, dysentery, hepatitis, and Legionnaires' Disease. Botulism, cholera, smallpox and typhoid fever are further maladies Hydro-Photon Inc. can guard against.
I tested the pen out in streams and lakes this summer, and as far as I know the system worked. There's a bit of magic and technology to trust, as well as the company's word on what the product does, as water treated with the SteriPEN seems the same before and after the treatment. All the action happens on an unseen microbial level.
I found it to be more quick and convenient than a pump filter. Iodine pills, a long-time favorite of mine for their simplicity and portability, leave a funny aftertaste; the SteriPEN has no such side effect.
For nasty water you will have to pre-filter before using the SteriPEN, running the bad water through a product like the company's Water Bottle Pre-Filter, a $12.95 cap that fits atop Nalgene-style bottles to catch debris and particulates.
Or, in a pinch, you can just use your underwear. The SteriPEN, hopefully, will take care of the rest.
Stephen Regenold writes The Gear Junkie column for eight U.S. newspapers; visit www.thegearjunkie.com for video gear reviews, a daily blog and an archive of Regenold's work.