Estimating the Age (Lifespan) of Your Backcountry Water Filter

[Jon Fong]

Companion forum thread to: Estimating the Age (Lifespan) of Your Backcountry Water Filter

The goal of this test is to determine the effective age of your backpacking water filter based on comparing its current flowrate to its flowrate when new.

[Rex Sanders]

Hi Jon,

Thanks for the detailed background and analysis. Would be great to gather more data across several filters and filter models, but that requires a lot of work.

It seems like filters more-or-less gradually decline until (a) they stop working entirely or (b) I get too frustrated with the flow rate and decide to buy a new one. Generally, I try filtering some tap water just before each trip to make sure it still functions acceptably, and hope for the best. Maybe tracking flow rates with a repeatable scheme like yours would help me forecast that replacement date more accurately, and prevent backcountry surprises.

— Rex

[Casey Bowden]

Jon,

Great article. I don’t think I’m up to tracking the flow rates of my BeFree, but in the future I think I will:

• Filter tap water just before the trip to make sure the filter still works OK (good idea Rex)
• Bring a spare BeFree filter (it’s only 1.5 ounces)

Casey

[Jon Fong / Flat Cat Gear]

I believe that if this community got together to measure the performance of brand new water filters it would establish a good database.  Sawyer, BeFree, whatever.  I suspect the measurements of new filters will be very repeatable.  After that, everyone could get a sense of the remaining filter life of their respective filters.  At the heart of this is the UL concept of reducing redundancy via smart decision making.  With my 5 year old filter, I was flying blind until I got the data.  My 2 Cents

[Terry Sparks]

<p style=”padding-left: 40px;”>I find it interesting that most backpackers will backlash their filters, which is what the manufacturer recommends and what I did for years.  While hiking thru the 700 miles of New Mexico on the CDT,  I started soaking the filter in warm water (110*-120*F)  for 20-30 minutes, shaking it out, then backflush for better results.</p>

[Jeff McWilliams]

I just got back from 2 weeks on the JMT and used a 2-year old Sawyer Squeeze.  For this trip, I switched from using the Evernew 2L bags to the CNOC Vecto 2L bags, because the Vecto bags have a clip that can be removed to completely open the back end of the water bag.  This makes it much simpler to fill the bag, particularly in standing water.

However, I wasn’t very happy with the performance results.  When I would roll the CNOC bag like a toothpaste tube and put pressure on the bag, the flexible silicone like material would bulge rather than directly transfer all of my exerted force into water pressure.  The result was that I felt it took me longer to filter the same amount of water with the CNOC bags than it did using the Evernew bags.

When I got home, I tried filtering clean water through the Squeeze using my Evernew bag, and was disappointed to see that the flow rate just wasn’t what I remembered it to be. While on the trail, I backflushed the filter 4 or 5 times using the included syringe, and I backflushed it again when I got home.

I also flushed a diluted amount of CLR through the filter prior to our trip.  There’s a separate discussion about Sawyer and Katadyn BeFree flow rates, vinegar, CLR, and hardware scale deposits that can occur when sanitizing filters with bleach and hard water sources.

On a whim, I decided to back flush my Sawyer again, this time using the blue female-female coupler sold by Sawyer, and by connecting the filter directly the faucet of my utility sink to achieve higher pressure.

Back flushing at this higher pressure and volume appears to have made a marked improvement in performance.  Far greater than my best attempts at back flushing the filter with the syringe.

Sadly, I did not measure before/after flow rates to quantify the change.

I would encourage others with a Sawyer filter and the blue female/female coupler to try back flushing by attaching the filter to your utility sink faucet.   You may have to first unscrew the aerator from your faucet if your utility faucet has one.

P.S.  The connection to the sawyer filter using the blue coupling connection wasn’t completely water tight.  Some water still sprayed out at the connection.  I just loosely wrapped my hand around the connection to prevent the leaking water from spraying up into the air and making a wet mess in my laundry area.

 

Regards

Jeff

 

[Arthur]

Jeff  go outside and use a hose and let it leak!  I worry that the high pressure could have damaged the filter, thereby making flow faster by creating broken fibers and sideflows.  Is there any particle out there that is colored and the same size as a bacteria to use to see if it gets thru the filter as a test?

[Jeff McWilliams]

From https://www.sawyerdirect.net/FAQWaterProducts

The fibers are very robust so please be FORCEFUL in your back flush process. When using the syringe do not be gentle, it will only form paths of least resistance instead blowing out the particulates that may be trapped in your filter. When using the faucet adapter, hold the adapter on the faucet and ‘turn the water up’ to ensure particle(s) removal.

From https://www.sawyerdirect.net/sp174

This Sawyer Faucet Adapter is for all Sawyer Water Filters and Purifiers. It connects the inline filter/purifier to most water taps. The adapter head is made of flexible PVC, which allows connecting to several different size faucet mounts. This faucet adapter is used for backwashing all Sawyer Filters and Purifiers, extending their life.

The SP174 adapter is now very difficult to find, so I figured the coupling adapter was equivalent.

 

[James Marco]

I could suggest a slight improvement to the test apparatus to hold pressure (from gravity) constant as the bottle empties. Attaching the bottle to a longish spring (like a screen door spring) would raise the whole thing as the water flows out, but any improvement would be minor. You have a pretty solid testing apparatus.

[Jon Fong / Flat Cat Gear]

I recently purchase a Sawyer Mini and conducted the same test.  The time to filter 500 ml was 150 sec so the approximated filter area is 56.7/150 or ~38% of the filter area of the Sawyer Squeeze.

Saywer Squeeze ~ 3 oz (~$30)

Sawyer Mini ~2 oz (~$20)

The Sawyer Squeeze has about 3 times the filter area as a Mini and cost $10 more.  IMO, that’s money well spent.

[Jon Fong / Flat Cat Gear]

I recently updated my filter flow test, instead of using a scale I used a graduated cylinder to measure fluid volume.  Additionally, I did some number crunching on the data and came up with some interesting results.  By using a new Sawyer Squeeze filter as a baseline, you can use the effective area of the filter (new=ideal) to make comparisons between new and used filters.  Additionally, when compared to a new Sawyer Mini filter, you can estimate potential performance.  In my analysis, I had three real data point: a new Sawyer Squeeze, a new Sawyer Mini and a 5-year-old Sawyer Squeeze.

 

The Highlights are as follows;

1. A new Sawyer Mini is over 2 times slower than a Squeeze
2. After 5 years of use, my Sawyer Squeeze required about 50% more time to filter as a new Squeeze. The time to filter 500 ml went from 68 seconds to 103 seconds.
3. If I had used the Sawyer Mini instead of teh Squeeze over those same 5 years, the flow rate would require 340% more time than a new Mini. The filtration time to filter 500 ml would have increase from 155 seconds to 680 seconds.  This seems to corelate to a lot of observations that the Mini clogs frequently.

Here is the testing video

Here is the number crunching video

Jon

[Jerry Adams]

the other thing about hollow tube filters like sawyer squeeze is don’t put bleach in it if you have hard water.  That will clog up the filter.  But you can use CLR/vinegar to clear it like Jeff said

maybe the model of a filter gradually clogging up applies more to conventional filters like PUR or MSR?

with a hollow tube filter like Sawyer Squeeze, if you backflush it clears most of the pores?  It would be interesting to test a new filter, then test it occasionally for a few years.  See if the flow rate gradually decreases.

maybe sawyer squeeze lifetime is determined by one bad incident, like freezing it.

does anyone have a Sawyer Squeeze they gave up on because it was too slow because it gradually clogged?  even though they used optimum backflushing as mentioned above – connect to faucet, use warm water/CLR/vinegar?

I’ve used my Squeeze for 6 years and it works pretty much the same as new, although I haven’t measured it.

Regarding freezing, if you shake all the water out of it then there’ll just be water in the hollow tubes, but they’re designed to expand when you backflush so they should withstand freezing

Too bad there isn’t some solution that contains colored particles of some size greater than 0.1 micron.  If they get through the filter you could see it.

[Author]

Posts