How to Clean and Flush a Backpacking Water Filter

Proper gear care helps you prolong the life of that gear, and in the case of water filters, it can also increase the performance and flow rate. Something like a water filter or any water purification system is invaluable in the backcountry. Without fresh, clean water, any adventure can go sideways fast. 

Although there are several water purification methods, a water filter is one of the easiest and most commonly used. We overview a few types of filters, but the main focus of this how-to guide is to walk you through the steps of backflushing and cleaning a water filter element. 

Types of Water Filters

The first thing to note is that water filters and purifiers differ. The primary difference between these two is the size of the microorganisms they catch and remove from water. 

Water filters remove protozoan cysts and bacteria. Protozoan cysts include Giardia lamblia. Bacteria include Salmonella and E. Coli, among many others. Water filters are great for travel within places like Canada and the United States, where biological pathogens like these are the primary concern. 

Viruses are generally too small for a water filter to effectively catch and remove, which is where water purifiers come into play. Water purification methods are recommended when traveling in areas with higher cases of contaminated water or virus exposure through the water. 

All water filters contain a filter element (or cartridge), but only some water purifiers have them. Many purifiers use chemicals (like iodine or bleach) to kill viruses. Any water filtration or purification system that contains an internal filtering element needs to be cleaned or backflushed occasionally for best results. 

Pump Filters: a pumping mechanism that has an intake hose you drop into the water and an outlet hose to put in your water container. There are various options available for pump filters and how hard they are to pump, the flow rate, and other specs will be different for each one. 

Bottle Filters: essentially a water bottle that has a filter built into it or can be added. All you do is fill the water bottle and then drink from it. The filter or purifier cleans the water as you drink through suction or pressure to move the water through the filter before drinking. The filter is fully contained and operated within the water bottle. 

Squeeze Filters: similar to a bottle filter, but the filter is on the outside of the water reservoir or container and is what you drink directly from as it filters the water. 

Gravity Filters: generally a pair of reservoirs with a filter you attach between them. To use, fill one reservoir, connect the filter to both reservoirs, and find a place to hang it. Size and flow rate varies from model to model. 

Straw Filters: the most common straw filter is the Lifestraw. All you do is stick the straw in a water source or water bottle and drink through the filter. It is a filter-on-demand situation. 

Other available methods of purifying water that does not include a filtering system are UV purification, chemical purification, or boiling water. 

How to Backflush a Water Filter

Backflushing is reversing the typical flow of water through the filter element. This is done to unclog and remove any built-up sediment and debris. Over time, if the sediment is allowed to collect without flushing, your flow rate will slow, and the filter could stop working. 

The process of backflushing isn’t necessary after every trip. Plus, there are some things you can do to help you avoid doing it too often. Regardless, the reality of backflushing and keeping your water filter clean is not difficult, and it does not take all that long. It will improve the flow rate and can ensure that you have a fully functional filter for the next adventure. 

Some filters have a removable element, while others have a plunger-style system that does not require disassembly to clean. Many filters, like the Sawyer Squeeze water filter, come with a syringe that makes backflushing simple and easy. Others may use a hose or even require shaking. For many pump filters, you may need to remove the filter element altogether, allowing you to wash it by running it under water. The brand and type of filter will impact how you backflush the element, so follow manufacturer guidelines for best results. 

Backflushing a filter right after a trip when it is still wet tends to be easier than doing it after your filter has sat in storage for some time. If the filter is dry, filter some water through it in the typical direction to get it wet before backflushing. 

Remember, not all water filters or purifiers have the same type of internal filter element, and they are not all of the same durability. Using too much pressure during backflushing can damage the filter element depending on the filter’s durability. So we want to emphasize following manufacturer guidelines while performing a backflush.

How to Sanitize a Water Filter

Sanitizing the filtering element isn’t always necessary but is often recommended by manufacturers to be done before long periods of storage. After you’ve backflushed the element, sanitizing it kills any leftover microorganisms that may grow or form with time. 

Since not all filter elements are the same, much like backflushing, the method of sanitation changes from brand to brand. Many brands overlap in methods and may recommend a solution of diluted bleach or the use of Aquamira drops. 

FAQ

Regardless, our number one recommendation is always to follow manufacturer-specific instructions to ensure you do not damage the filter and that the materials are adequately sanitized.