For the backpacking enthusiast water treatment is essential. Boiling water and waiting for iodine tablets will remove most harmful bacteria and viruses, but both are time consuming and certainly less than ideal. That then leaves the water filters or purifiers as the most viable option for the backpackers among us. What then are the differences between the two items and how do you chose which item to purchase?
Most filters on the market operate with a small pump that pushes water through the filter itself. Over time, the filter has a tendency to become dirty and requires cleaning and eventual replacement of the inner filtration elements. Filters are made of plastic, ceramic, and metal, and all have varying levels of effectiveness and durability. No matter which type of filter you have, weight will be added to your pack over a water purifier.
Purifiers do not remove any debris from water--they merely eliminate any harmful effects from particles lurking in water. With that being the case, it is recommend that you fill your container from a body of moving water.
There is no clear winner in this debate as both the filter and purifier have their advantages. Unlike a filter, a purifier eliminates viruses, but generally, these viruses are rare depending on your location. The water filter eliminates debris from water but also weighs more than a purifier and can be more difficult to maintain. Cost wise, purifiers tend to be a little more expensive than a water filter. But, ultimately, it comes down to user preference and peace of mind when deciding how to treat water when you are in the back wilderness.