Whether you are journeying on a shorter day hike, or a multi-day backpacking excursion, accessing fresh and clean water is paramount to safely and successfully completing your trip. Although water is so crucial, it is often one of the heaviest items in a backpacking bag. Seasoned outdoors people often bring water filters, water purifiers, and pre-filters to lighten their load while still being able to replenish and refill their bottles. Even though common wisdom dictates that clear water from a running source is generally safe to drink, in the backcountry, pristine spring water can still cause illness and be invisibly contaminated. In this list, I’ll outline the differences between the common forms of water filtration and purification and then speak to the optimal times to use each method. Remember that there is more to the best water treatment practices than purification and filtration. It’s important to not cross-contaminate clean and unclean water containers, to keep all your anthropogenic water needs at least 200ft from natural water sources, to clean your hands with hand sanitizer, and finally, to seek out sediment and silt free (running) water.
Water filters, purifiers, and pre-filters
Purifiers offer the greatest protection from contaminated water. Water filters generally work by physically inhibiting waterborne protozoa and bacteria from passing through the filter. Due to this, water filters often need to be cleaned in the field to prevent too much debris from building up in the filter, and ultimately, they will need to be replaced. On the other hand, water purifiers are designed to remove protozoa, bacteria, and viruses. Although a small portion of technologically advanced water purifiers employ pores that are small enough to physically stop viruses from entering your clean water, in general, they use UV light or chemical treatment to kill viruses. While water filters are suitable for much of the backcountry in the United States, where viruses are uncommon due to low human traffic and influence, they might not be suitable for your water needs in undeveloped areas. Furthermore, both water filters and purifiers include activated ingredients in their systems that improve the taste and remove the chemical presence from the filtered water. Additionally, water filters and purifiers often come with pre-filters, although you may need to purchase one for certain systems. The benefit of the pre-filter is that it decreases the need of cleaning the filter, increases the lifetime of the product, increases the efficiency of the filter, and reduces the sediment and silt imbibed.
Pump filters require the user to manually pump water through the physical filtration or purification system. Although pumping can prove difficult as the system ages, many modern pump systems have auto-cleaning aspects that greatly improve the efficiency of your system. Furthermore, the ability to filter certain amounts of water saves time while on the move. Pumps are especially useful from shallow water sources, pools within nooks and crannies, and water bodies that are only accessible from a small area due to large debris.
Bottle filter and purification systems are convenient for day hikes and short-duration backpacking trips. Featuring replaceable filtration elements, the main life-span determinant for these systems is how willing you are to replace the filtration element. Be wary of the protozoa, bacteria, and/or viruses that these systems filter, and pay special attention to the field instructions for how to clean the element.
Similar to bottle filters and purification systems, squeeze filters require manual labor to squeeze the unclean water through the filtration element, but provide instant clean and safe water. Since squeeze filters are lightweight and can often double as a gravity or straw filter, they are often a go-to on all sorts of outdoor excursions. Pay special attention to the fact that most squeeze filters are not suitable for removing viruses from water.
Straws are a go-to for ultralight backpacking setups as they are low-weight, provide instantly clean drinking water, and are usable directly at the water source, or from a bottle that is filled with unfiltered water. The main drawbacks of straw filters are that they are usually only a solution for a single person and that while they have long lifespans and will successfully filter water for many trips to come, they are usually irreparable, and ineffective once the filtration element wears out.
Gravity filters and purifiers are best for large groups of people or morning and evening camp setups where lots of water will be used. Although they typically need larger water sources to fill the unfiltered water reservoir, the reservoir can also be filled with ease from moving water sources. The benefits of gravity filtration and purification systems are replaceable water cleaning elements, and a lack of manual labor as gravity pulls the water through the element, but a major drawback to be cognizant of, is that finding a place to hang the reservoir is not as easy as it may seem. Furthermore, in certain situations it will be very difficult to fill up the reservoir, rendering the water cleaning system useless. Finally, gravity filtration and purification systems are not good for those on the go, as they often take significantly longer to clean water than pumps, bottles, straws, and squeezes.
UV purifiers are often pen devices that the user will hold inside a bottle of unclean water to purify the water and make it safe to drink. Although UV purifiers are efficient, when it comes to larger quantities of water, water pumps generally take the cake. Furthermore, UV purification systems will require a pre-filter if the water contains sediment or other contaminants because while the UV light will effectively kill protozoa, bacteria, and viruses, it will not break down silt.
Chemical water purifiers are often physical tablets or solutions that are then added to water in low quantities. Although chemical purifiers are inexpensive, ultralight, and easy to use, they often leave a chemical aftertaste and can be ineffective against the cryptosporidium protozoa. The main drawback of chemical water purification is that it can take from half an hour to four hours (due to freezing water) for the purification process to be completed. I would recommend them as a backup on long backpacking trips, but would not recommend them as a main purification method unless they are absolutely necessary.
Boiling Water to Purify
Last but not least, bringing water to a rolling boil for one minute, or three minutes above 6,500 feet, will effectively purify water from protozoa, bacteria, and viruses. Although this water will need to be pre-filtered, boiling silt-filled water won't actually increase the time of boiling needed to be effective. The main drawback of this treatment method is that extra fuel will need to be carried or gathered to sustain the time required to boil water. I would recommend remembering the time benchmarks needed for cleaning water through boiling it, but again, I would not recommend this purification method as anything other than a backup.