Picture this: you dig your camp water filter out of storage at the first sign of spring, head to the kitchen to make sure everything is in working order, and your heart sinks as water barely trickles through.
The good news is that the filter may not need to be replaced, it may just require a good cleaning and that you update your off-season storage practices. So to keep your camp filter flowing freely for as many hiking seasons as possible, take a few preventative and protective measures before you stash it away for a few months.
Clean your filters before you put them away
The key to top-tier water filter performance at the beginning of every season is to stow your filters clean. And possibly wet, though that largely depends on the filter brand in question. We’ll get to that.
Many filters intended for camping, hiking, and backpacking get the job done via a hollow fiber membrane. These products remove unwanted material from natural water sources via a cluster of microscopic straw-like structures with holes so small that organisms like bacteria, parasites, dirt and microplastics can’t pass through. They’re a lot like a fine strainer that lets water pass through but traps your penne noodles.
And like a strainer, the more you pour through a filter without emptying or rinsing it out, the lower the flow-through rate will be. So if your filter won’t filter on the first trip of the season, it’s likely because any contaminants that didn’t get flushed out before you put it away may have grown, multiplied, or crusted over, making the flow sluggish at best and ineffectual at worst.
Flush out your filters
Start by backflushing your soon-to-be-stored filters. Most high-quality products come with a backflush tool that resembles the plunger on a syringe. Attach it to the end of the filter from which the clean water exits and use the plunger to force water backward into the device. This will help dislodge any stuck particles clogging filter pores. If your filter is dry, run water through in the normal direction first to lubricate it. If your filter is especially clogged or slow, you may have to flush it several times. This process can often restore up to 95 percent of a filter’s flow rate, according to Travis Avery, marketing director at filter manufacturer Sawyer.
Remove any carbon inserts
If you have a filter with a carbon insert, remove it before you sanitize or flush your filter with anything other than tap water. Store it separately in a sealed zip-top bag or airtight container. Carbon absorbs contaminants from anywhere, even air, and pushing any sanitizing agents through (see the next step) will significantly shorten its lifespan.
Sanitize your filters
Once a filter is clear of microscopic debris, both Avery and Tara Lundy, a spokesperson for filter brand LifeStraw, recommend sanitizing the inside with a bleach or chlorine rinse. Add one capful of bleach to a liter of water and force it through the filter in the usual direction of flow. This will kill any pathogens still lurking in the membrane and will also banish any residual foul taste.
Decide if your filters need to be wet or dry
The route you take here will depend on what filter you have, so check your manufacturer’s directions before proceeding. Filters vary, after all, from pore size to hydrophilicity.
If your filter membrane is hydrophilic, meaning it has a molecular attraction to water and is most efficient when wet, dry storage can cause problems. When one of these filters completely dries out, it can be difficult to get water to flow through again because air or other gasses may have become trapped in the membrane. These can be tricky to displace, Lundy explains.
[Related: Survive the great outdoors by making your own drinkable water]
Worse, if the filter wasn’t completely clean and sanitized when it dried out, particles and contaminants—even those that are invisible to the naked eye—can become caked onto the membrane, clogging the straws and making you think you need a new filter.
Think of filters like dishes, Avery says. If you rinse and wash your dirty dishes right after you use them, they’re much easier to clean than if you let them sit on the counter overnight to get crusty. Once that happens, scrubbing becomes an infinitely more tedious and time-intensive endeavor.
Dry storage
Avery advises dry storage, particularly for Sawyer filters that use proprietary self-priming membrane technology. These products aren’t as susceptible to trapped gasses interrupting flow. To dry out your filter completely, leave any caps or closures open and let it air out before packing it up. This might take a few days, depending on temperature, humidity, and other environmental factors.
Wet storage
Lundy, meanwhile, recommends storing your filter wet—the preferred option for LifeStraw products. But stashing your device full of tap water can lead to bacteria and algae growth, so you’ll need to use salt water to prevent that. Fill a bowl with 2 cups of water, add 1 teaspoon of salt, and stir until it dissolves. Force the saline solution through the filter in the normal direction of flow.
Put caps or lids in place to keep the salt water inside the filter and secure it in a zip-top bag or similar vessel before packing it away. This will help keep the hydrophilic membrane lubricated so it’s good to go when the next camping season rolls around. To flush out the salt water before your next use, blow any remaining solution out of the filter by pressing it to your lips and huffing and puffing into it in the direction of flow and flush clean water through it to clear out any remaining saltiness. If the filter functions like a straw, suck clean water through and spit it out until there’s no more salty flavor.
This works because continuous wetness helps these types of filters maintain the highest level of performance, Lundy says. That’s because hydrophilic membranes draw water in, spontaneously entering and filling pores. When wet, the membrane will not allow air or other gasses to pass through, which helps maintain a strong flow rate.
Camping water filter storage tips
Caring for your filter and protecting its flow rate isn’t the only thing you can do to prolong your product’s life. Cold temperatures are just as—if not more—detrimental to longevity as clogged fibers.
“Ice expanding can destroy the integrity of the pores,” Lundy says. That’s because when water freezes—including small droplets inside the fibers—it expands and can puncture or break fibers, making your filter effectively useless. So always stow used filters in a climate-controlled environment where there’s no risk of freezing. Filters that haven’t been used are not at risk.
And if your filter is particularly sluggish after pulling it out of storage, Lundy suggests soaking it in a solution containing a hydrophilic agent such as coconut milk: 4 tablespoons mixed with 2 cups of water. After one hour, rinse the filter clean water and voilà—hydrophilicity restored.
Whatever filter you own or storage method you choose, care for it well and it can last for years. Just be sure that no matter how you stored your filter, give it a good forward flush with clean water. Lundy even suggests performing another bleach rinse to ensure there has been no algae build up during storage. After all, you don’t want to take all the proper precautions just to take a nasty sip of who-knows-what on your next trip outdoors.