Here’s the difference between portable water filters and purifiers — and how to know which you need.
Gone are the days when hikers could just sip from a trickling, crystaline stream for refreshment. Whether you’re spending a week in the backcountry or backpacking through Thailand, you’ll want to treat your water to make sure you don’t spend most of your vacation exclusively checking out a new country’s public restroom scene.
“I don’t need this,” you may frown, “my hotel room comes with bottled water.”
Perhaps reconsider. There certainly isn’t a shortage of discarded plastic in the world, about eight million metric tons of which end up in the ocean every year. Think of the sea turtles. Or think of yourself, eating fish who have been eating dissolving plastic, or lounging on a beach where waves of empty bottles gently lap at the shore.
Now, let’s discuss some reusable options.
The key thing to note here is the difference between a filter and purifier. A filter will remove physical sediment (dirt, microplastics); protozoa and cysts (cryptosporidium, giardia); and bacteria (E. coli, salmonella), and usually improve the taste of the water as well. However, it usually has slightly larger gaps in its filtration system, which will allow smaller viruses (hepatitis A, norovirus) to sneak through. A purifier will kill protozoa, cysts, bacteria, and viruses, but it won’t do anything to the consistency of the water. Boiling, for instance, is one of the original purification methods that's ineffective for sediment — you can boil water with pebbles in it all you want, and the pebbles will still be there.
“If you are in a pristine backcountry area, viruses aren’t an issue, but they are a huge issue in urban areas or even backcountry streams that are near urban areas or rangeland,” says Backcountry Gearhead Lisa Edlund. “Anyone traveling to another country will want to have a purifier.”
There are pros and cons to each method. According to Edlund, water purifier bottles are some of the easiest and fastest methods if you only have a small volume of water. A pump filter will work better for large volumes of water, but most are larger, pricier, and harder to carry. A UV pen, meanwhile, is a simple purification option, but it won’t work on murky water, as the light won’t be able to reach as deeply as it needs to. Chemical treatments won’t have that problem; they’re reliable, simple, and portable, but can take significantly more time and change the taste of the water.
You can double-up a filter and purifier; for example, use a pump to get filtered water into your bottle and then a UV light for purification. Both the CDC and REI go into the process in more detail if you’d like to be extra thorough.
We consulted some extensive testing websites along with more general lists, travel blogs, and frequent travelers to see what the strongest contenders are for keeping you safely hydrated.