Turning on the spigot to fill a large metal pot of water at the Eiseman Hut, I was thirsty and just assumed it was clean. The 10-mile skin into the 11,180-foot backcountry lodge left me high and dry while carrying supplies for the week. The water had been boiled atop the wood stove and of course it was safe to drink... right? I instantly downed a huge gulp then spat out ashes and dirt. Luckily I had brought along my SteriPen, a battery-powered UV water-treatment device. While it wasn't going to filter the ashes (I left that part at home), I grabbed a coffee filter to sift out the floaties and zapped it with the pen. Deep in the backcountry, I wasn't going to take any chances.
Having the ability to treat water anywhere is a valuable tool, especially while backpacking, touring in remote areas, or for long extended treks in a foreign country where you're not sure you'll find clean and trustworthy sources. The three I’ve tested below are lightweight for skiing, and turn potentially sketchy water sources into refreshing hydration.
The simplicity of Grayl's water purifier is hard to beat. Just fill-up the super light bottle (10.9 ounces) to the designated line, insert the inner press that has a filter at the bottom, and press down (like a French press coffee) to create safe and good-tasting drinking water. The system utilizes an ultra-powdered activated carbon filter (rated for 300 uses) that sifts particulates, heavy metals, and doesn't have the bad taste/smell that those iodine and chlorine droplets contain.
It also removes 99.9999 percent of viruses such as Hepatitis A, SARS, Rotavirus, along with bacteria such as E. coli and Salmonella. So if you're questioning the source of water, or if there are some floozy-looking moose and beaver near your backcountry yurt, then avoid the chance of getting sick--simply press and go.
This is one of the lightest (2.3 ounces) and more popular water-bottle filtration systems, according to my local REI store, and for good reason. The one-liter bladder flask is compact and can easily stash into a full backpack. Once full from a backcountry water source, you can either squeeze the bladder or tip it upside down to get the water to flow through the filter and spout.
The 1 micron microfilter (rated up to 1,000 liters) is 99.99 percent effective at removing organisms and 99.9999 percent effective at removing bacteria such as E. coli, Giardia, etc. It's super convenient and fast at providing drinking water in the backcountry. The taste is clean and fresh, but did have a bit of a plastic flavor.
I've brought the SteriPen on several backpacking and backcountry ski trips. While it has the appearance of a futuristic space-like probe, it's super useful when you're in a bind. The system weighs only 6.3 ounces, getting heavy only from adding batteries that can take standard AA or rechargeable lithium. The upside is you can use any water bottle on hand (it works best with one liter), and fill up several on the spot--purifying one liter of water in 90 seconds.
The sensor in the SteriPen detects when it's in water and illuminates the bottle. It then has indicator lights, signaling the water is safe to drink (destroying 99.99 percent of protozoa such as Giardia, bacteria, and viruses). With fresh batteries, it's stated that it can clean 50 liters, but I usually swap batteries before I take it out and the system can stand approximately 8,000 cleans. It also comes with a prefilter to remove particles such as twigs, dirt, or ash from that nasty lodge pot of water.