Sure, you can usually buy bottled water instead – but the amount of discarded plastic in formerly-pristine parts of the world leaves many travelers not wanting to add to the problem.
It's also not unusual for unscrupulous vendors to refill bottles themselves to save money, or you may be far enough off the grid that bottled water simply isn't available.
Whatever the reason, the good news is that lack of bottled water doesn't mean you need to risk your health. There are several different, highly-portable ways to treat water from almost any source yourself.
Free-flowing water is best, but as long as there aren't many physical impurities like mud or dirt, any of these methods will remove nearly all waterborne parasites and bacteria.
The lightest, lowest-cost option for treating water has been around for decades – a jar of iodine tablets. You'll likely pay well under $10 for a pack that will provide 5+ gallons of safe water, and they take up virtually no space in your bag. There are no parts to wear out or batteries to go flat, and an unopened pack will last several years.
There are a couple of negatives, however, which do put some people off. Iodine tablets take at least 30 minutes to be effective, so they're not ideal if you're parched right now. More importantly, they also leave a noticeable taste that isn't exactly pleasant. It's better than getting sick, but it's probably not something you'd volunteer for given the choice.
Finally, iodine isn't effective against Cryptosporidium, a parasite spread by human and animal feces that causes “Crypto,” one of the most common waterborne diseases in the US.
Steripen has been around for several years now, producing over a dozen different versions of its portable UV water purifiers for different markets. The company offers several models for travelers, but all offer the same basic function: purifying a half-liter of water in under 50 seconds.
Travelers benefit from the rechargeable battery included in the Ultra model which also comes with extra features such as a screen or being particularly lightweight. If you want to save a bit of money, there's also the Aqua version -- but you'll need to deal with the hassle of buying and replacing batteries.
It's a quick and simple approach to purification, but since it uses ultraviolet light, it works best with clear water. The company also offers a pre-filter attachment that fits on several types of water bottles, to help remove particulate matter before you start.
Taking a different approach, the Grayl resembles nothing so much as your favorite coffee maker. Looking much like a typical French press, the device purifies water by forcing it through a special filter using simple downward pressure.
Previous versions of the gadget had several types of filter, but the company has sensibly decided to simplify things for the latest model. The best filter is now the only one available, so you don't need to worry about exactly how polluted your water happens to be when you're treating it.
The Grayl will also get rid of several types of chemicals and heavy metals, so the water tastes better as well as being safer. The only real problem is the relatively small 10.9 oz capacity of the container, but if you know you can refill and treat water from any source while you're out, it's less of a worry.
The filter takes 15 seconds to process its full capacity, and lasts up to 300 cycles (40 gallons), at least if you're using clear water without dirt or other solids in it. That's around three uses per day for three months -- plenty for all but the more hardcore travelers and hikers. Extra filters are available for those on extended trips.