Have you ever been traveling in a foreign country and been afraid to drink the water? I have. Especially when the guidebook says, "Tap water in [country] is not safe to drink." But then the locals say they all drink the tap water, and you're not really sure what is safe and who to trust. When I was in South Africa recently, I kept hearing things like, "Well, you CAN drink the water here ... but I don't."
That's what's happening to me now, as I'm working and traveling through Belize. Before I left, I bought this little gadget that I really want to write about, because it's so useful, and (hopefully!) effective, especially when you are traveling for long periods of time and don't want to be constantly buying expensive bottled water. It's called the Steripen. It's a small, battery powered (CR123) handheld device that emits an Ultraviolet light that is effective against bacteria, viruses, and protozoa (like that pesky Giardia).
So what I've been doing, just to be safe, is filling my Nalgene bottles (yes, I have the new BPA-free ones!) with tap water, zapping them with the Steripen (1L takes less than 2 minutes) and I can drink all the water I want, instantly, and worry-free! The Nalgene bottles are nice to use with this Steripen because you need a nice wide-mouth bottle.
The Steripen has a light on it that blinks green if your purification has worked properly, red if it hasn't. I've used it about 10 times so far and only had one red light incident. (I think I may have pulled it partly out of the water while using it. Got the green light on the 2nd try.) Although I tend to prefer fail-safe products that can't break (or run out of batteries), this thing is really useful. You can always carry water purification tablets with you as a fail-safe back-up if you are backpacking or camping. The nice thing about the Steripen is that you don't have to wait 4 hours to drink your water.
Here's a video of it in action in Belize: