What’s the difference between a backpacking water filter and water purifier?
Put simply, the main difference between a filter and a purifier lies in the level of protection they provide against harmful microorganisms that may be lurking in backcountry water sources. Generally speaking, a water filter is designed to remove waterborne protozoa and bacteria, but not viruses. A water purifier is designed to remove protozoa, bacteria and viruses, offering a higher level of defense by combating all three.
Why the two treatment device options?
Traditionally, tackling viruses has poised a unique challenge for water treatment. On the microscopic scale, viruses are far smaller than protozoa or bacteria. Because of this, they’re too small for backpacking filters to catch; they slip through the filter media that filters use.
Until recently, UV light, chemical treatments or boiling were required to deactivate viruses by scrambling their DNA or killing them. Now, however, advancements in mechanical pump purifiers provide a convenient way to physically remove viruses, along with bacteria and protozoa, in one easy step.
Still, it’s not always considered necessary to carry a purifier on every trip. Let’s take a look at why.
(Please note, the COVID-19 virus has not been detected in drinking water supplies, according to the World Health Organization. Municipal systems readily tackle waterborne pathogens in their treatment methods.)
When should I use a backpacking water filter?
While purifiers offer greater defense, they’re not always deemed necessary.
If you’re traveling in the backcountries of the U.S. and Canada, a filter is considered sufficient protection. In these pristine landscapes, where human traffic is relatively low, protozoa (like cryptosporidium and giardia), and bacteria (like E. coli and salmonella) are considered the main threats.
Viruses are, most often, specific-specific. That means, viruses that harmful to humans are transferred primarily through human feces. Therefore, where there are fewer humans, we assume the risk of viruses is also lower.
However, it’s important to ensure that your microfilter is built to handle backcountry-type water. Some filters in outdoor shops are designed to remove only unpleasant tastes from tap water. Backcountry-grade microfilters are designed to remove contaminants down to 0.2 microns and should meet NSF protocol p231 and/or the U.S. EPA’s Guide Standard and Protocol for Testing Microbiological Purifiers (for removal of bacteria and protozoa). Learn about these testing standards here.
When should I use a backpacking water purifier?
If you’re traveling to less-developed countries, where water treatment and sanitation infrastructure is poor, a water purifier is the safer option. But, you might also choose a purifier in your local backcountry zones if you notice that people don’t practice good hygiene near water supplies—such as popular lakes.
Common waterborne viruses found in water sources include Norovirus and Hepatitis A.
If you already own a microfilter, you can use it to first filter the water of protozoa, bacteria and any particulate like dirt. Then to combat the viruses, use a purifying agent like chemical tablets, rendering the water safe to drink.
Using a purifying agent, like chemical tablets or UV light, alone won’t remove particles like dirt from the water. Particulate in the water can impede the effectiveness of UV light and to a lesser degree, chemicals.
This is where mechanical pump purifiers offer a big advantage.
Mechanical purifiers are designed to physically remove contaminants down to 0.02 microns (notice the extra zero in front of the 2). All mechanical purifiers should meet the NSF Protocol P231, NSF Protocol P248, or EPA drinking water testing standards.
As our local backcountries see a rise in traffic, and risk of viruses increases with it, purifiers may become the more popular tools of choice.
Three use scenarios to consider:
Here are a few scenarios that you might find yourself in while adventuring and the type of treatment device we recommend.
Backpacking in Washington’s North Cascades National Park:
You’ll be collecting water from subalpine streams and lakes along established hiking trails during the summer. Any pathogenic risks in the water will come from humans and animals, but are usually light in concentration. Here, bacteria and protozoa are the primary threats; the likelihood of encountering viruses is very low. The water may also contain particulate like dirt or sediment, which will need to be removed.
Treatment choice: A microfilter is typically recommended; but you might bring a purifying agent as backup if you suspect viruses could contaminate the water.
Camping on a holiday weekend at very popular lowland lake:
You’ll be collecting water from the lake, the shores of which are packed with campers. The higher concentration of humans leads to a higher risk of viruses. The water also contains particulates, which you’ll want to remove.
Treatment choice: A mechanical pump purifier, or microfilter plus purifying agent.
Hotel stay in Huaraz, Peru, before hiking into the Cordillera Blanca Mountains.
At the hotel, you’ll be collecting water only from the tap. Potential pathogens will come from humans and animals, carried to your faucet through a suspect water treatment system. Here, bacteria, protozoa and viruses are all of concern. However, the water is completely clear, free of particulates.
Treatment choice: A pump purifier, UV light or a chemical treatment.