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Hollow Fiber Backpacking Water Filter Care & Maintenance


Aaron Zagrodnick

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While many methods for backcountry water treatment exist, hollow fiber filters are quite popular due to their ease of use, effectiveness, reasonable cost, and longevity. While a hollow fiber filter is quite simple – with the filter itself having no moving parts and working through a multitude of hollow tubes (each hollow tube then having a multitude of microscopic pores, which actually filter the water) the filter element will still need to be maintained and some basic precautions should be exercised to maximize the lifespan of the hollow fiber filter.

Backpacking Hollow Fiber Filters - Care and Maintenance

Drops:

Every hollow fiber filter I’ve ever used has had precautions about dropping the filter – and although most have the actual element protected within a plastic housing, care should still be exercised. At home, store the filter on a low shelf or otherwise in some place where a drop would not be possible. On the trail, ensure that the filter is properly secured and stored. While I prefer to always keep my filter in an outside pocket of my pack for quick access during the day, we also need to make sure it can’t fall out easily if you happen to jump across a small creek. Water filters are one of those gear items where you can’t really tell if it’s working or not – if it’s working water comes out…just like if the element was compromised. Thus, I like to always look for a filter that comes with a manufacturer-approved integrity test that can be performed in the field – like the Platypus GravityWorks.

Freezing:

Just like drops, hollow fiber filters can’t be frozen if they’ve been used, as any water inside the tubes (which can never really be completely dried) could when freezing expand and fracture the element. This is a constant issue in mountain environments when it can freeze any night of the year. As such, when there is absolutely any chance of freezing I filter all the water I’ll need for the night, then disconnect the filter (if applicable to the system) and put the filter element in the foot of my sleeping bag at night in a Ziploc bag. If it’s still below freezing when you get up, you may then need to carry the element around in a pocket until it’s warm enough outside. Once the season gets cold enough where you’re carrying the element around all day or it never gets above freezing, it’s best to look towards a different water treatment method, of course.

Backcountry Water Source - Backflushing Hollow Fiber Filters

This pond, which was the best water around for miles in either direction, was full of algae and quickly slowed the flow rate of my hollow fiber filter. However, after a quick backflush the flow rate was easily restored.

Backflushing:

The flow rate for all hollow fiber filters will diminish over time and the dirtier the water, the faster this flow rate will fall. Luckily, hollow fiber filters can be rinsed or backflushed to help restore at least some of this flow rate, and this can usually be performed in the field. Look to the instructions specific for your exact system, but for gravity systems such as the aforementioned Platypus GravityWorks I currently use this simply involves filtering some water from the dirty bag into the clean bag, then raising the clean bag higher than the dirty bag, causing the clean water to flow back through the filter, taking dirt and debris along with it as it passes through. This dirty water can then be dumped on the ground. Other filters like the Katadyn BeFree can be cleaned by swishing the element in clean water. While backflushing will not make the filter perform quite as good as when it was brand new, keeping up with it and backflushing regularly can maintain acceptable performance for a surprisingly long amount of time. If you'll be backpacking where all of the water sources are questionable, you can also pre-filter your water with something like a bandanna to help extend the time you'll need between backflushes.

Disinfection:

After a trip, your hollow fiber will still retain some of that water you filtered along the way – whether that was questionable pond water or from a high mountain lake. Putting the filter right on the shelf could lead to all kinds of growth, be it algae, bacterial, mold, etc. Not only is this not appealing, but it can clog the filter over time as well as these types of growth are not easily cleared by backflushing. Unless you’ll be picking right up and heading out on another trip very shortly, it is best to disinfect the filter prior to putting it away in your gear stash. Once again, we’ll need to look to the specific instructions for your specific filtration unit to perform this task. However, most manufacturers suggest using household bleach diluted in water, then passing this solution through the filter.

An Inline Backpacking Hollow Fiber Water Filter

Make sure you’re using unscented normal liquid bleach for this task and diluting it as the manufacturer suggests. For example, with the Platypus GravityWorks, 2 drops of bleach in 1 liter of water is suggested. This can then be run through the filter to disinfect – and this solution will remain in the filter while it sits on the shelf to keep things fresh until your next trip. When that next trip comes along, I like the run a about half a liter of backcountry water through to clear out this solution. After a trip, I like to backflush first, then disinfect as a way to gauge what type of flow rate I can expect on my next trip – and to make sure it’s not time to order a new element. Hollow fiber filter elements aren’t exactly cheap either, and are usually the most expensive part of the system – with something like a replacement GravityWorks filtration element running about $55, I like to replace the cartridge only when I have to.

By taking these few simple steps you can maximize your water filter investment and avoid having to replace the element more often than you need to. And by taking care of your filter, you might be surprised just how long a hollow fiber filter can continue to serve you season after season. Need more info on all the common different backcountry water treatment methods and what’s ideal for different scenarios? You can read our guide on backpacking water treatment methods here. Check out a full selection of backcountry water filters (including those that utilize hollow fiber filters as well as other technologies) here at REI.

7 Comments


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John B

Posted

Aaron, I plead guilty to not flushing out my katadyn BeFree after trips, but leaving it with the residual water in the filter element.  I will consider myself chastised, and will try to do better!

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Aaron Zagrodnick

Posted

Ha - a little gear maintenance can be a good thing!

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angelfire

Posted

I always do a vinegar soak and then run some vinegar through my BeFree and Sawyer Mini before I leave for a trip because, more often than not, as the filter was drying from some previous trip, our hard water has deposited a thin coating of minerals inside the filter and little or no water will go through it.

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Aaron Zagrodnick

Posted

Thanks for sharing, I have seen where Sawyer does suggest a vinegar soak followed by running water through the filter for stubborn clogs / for situations where there could be calcium or hard water build up. I'm curious if you've seen if they suggest running vinegar through the filter however? I know Katadyn for example cautions against running anything other than fresh water through their BeFree. I haven't had issues with hard water deposits, however as an alternative, running the standard disinfection / backflushing process using distilled water (without added minerals) right after trips could be another option to flush out any (not yet dried out) hard water.

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angelfire

Posted

What I usually do is run a weak bleach solution through the filter when I come back from a trip, and then let the filter dry out as much as possible before storing it. I have learned (the hard way!) to do the vinegar soak, and then filter a couple of bags of water to flush out the vinegar, the day of or before leaving for a new trip. That way I know for sure that the filter is working. BTW, this vinegar process restores the really great flow rate to the BeFree, making it just like new. Also, I generally use the BeFree as my main filter and carry the Mini or a Steripen as a backup. On a short trip, when I am not worried about running down my batteries, I will filter first and then zap the filtered water with the Steripen, just for good measure.

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angelfire

Posted

I really like your idea of running distilled water through the filter before drying and storing it. I think I will try that after the next trip. BTW, in November we are moving to the North Georgia mountains, and I'm really excited about being able to backpack right out of my back door!

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Aaron Zagrodnick

Posted

I have done the same thing with a Steripen as well if viruses are of any concern, especially after filtering from something like a large river that’s downstream of a populated area. Try not to get water from a source like that but it can be the only option on some trips.

And sounds like a good move - living the dream! :)

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