The 3-Way Inline Water Filter is a solid top choice due to its rapid flow rate, incredible ease of use, and ability to produce insanely filtered water. Sawyer is notorious for top-notch filters. This one, if used correctly, offers exceptional protection from bacteria and protozoa since these organisms can't physically pass through the filter pores. Sawyer also makes a purifier that can remove viruses if that is a possible issue on your trip. When the filter is in place, you can simply fill up your bladder and immediately start drinking. If your water source contains large particles or sediments, it's a good idea to pre-filter your water through a cloth, microbag, or even a coffee filter before running it through the filter to avoid damage. The system also comes with a faucet attachment so you can filter tap water while traveling. To top it all off, you get a one million gallon guarantee, which means if you properly clean and care for your filter, it can last a lifetime.
The Katadyn Pocket Water Filter is an enduring favorite due to its reliability, durability, and versatility. This brick house of a filter is rock-solid, and can handle some hard core use and abuse. The ceramic filter is a breeze to clean with the scrub pad, and as long as you keep that filter clean, pumping is a breeze and the flow rate is stellar. A pre-filter on the intake tube helps keep larger particles away from the filter. The 20-year warranty isn't too shabby either. One potential downside is the weight of this filter (20 oz), but many individuals feel that its performance is worth the extra weight.
This filter is an excellent option if you want a lot of filtered water fast, and with very little effort. GravityWorks, as the name implies, relies on gravity filtration, and comes with two 4-liter reservoirs. Both have attached loops so you can easily hang them from whatever happens to be nearby. One reservoir is dedicated exclusively to clean, filtered water (for obvious reasons). In fact, the only way the "clean" bladder can be filled with water is through the filter itself: a design which prevents you from accidentally putting dirty water into both bags and contaminating your entire apparatus. A quick backflush at the start of each filtering session takes seconds, and will extend the lifetime of your filter. Just hang the bags, and in about two and a half minutes, you'll have 4 liters of filtered water.
These chlorine dioxide tablets are great for packing light, and involve no effort aside from dropping them into your water container. Adding one tablet per quart of water will kill viruses, bacteria, and protozoan parasites such as Giardia and Cryptosporidium. A potential disadvantage is the wait time for the tablets to work. Four hours is ideal for maximal purification, but you may not have to wait that long depending on water quality and the organisms present in the water. Planning your purification sessions ahead of time, such as right before bed, will make the wait time a non-issue. The tablets are individually wrapped, easily packable, and have a very long shelf life. Most users have found there to be little, if any, aftertaste. These tablets are a great addition to an emergency kit, and can be used in conjunction with a filtration system if you are extra-concerned over the quality of water that will be available during your trip.
The CamelBak All Clear is an extremely popular water purification system for domestic and international travelers as well as day hikers who prefer not to carry anything more than a water bottle. The system is extremely easy to use – simply fill the water bottle from your chosen water source (such as a tap, spout or stream), screw the lid back on, press the button on the cap to initiate the UV light, and gently agitate the bottle for one minute while the UV light works its magic. A 60-second counter will let you know when your water has been decontaminated of potentially dangerous microbes. You will eventually need access to a power source for a recharge, but plan on getting around 80 purification cycles with each full charge. If you plan on using this system during backcountry excursions or more rugged adventures, consider the separately sold All Clear Pre Filter to prevent any larger sediment or debris from getting into your water bottle prior to initiating the UV process.