How Long Will A Sawyer Squeeze Last?

I started the CDT with a brand-new Sawyer Squeeze and 2L CNOC Vecto. I left my old, heavy, MSR Dromedary at home. Instead, for spare capacity, I carried four of the 32-ounce (0.95L) pouches that come with a Sawyer Squeeze. The pouches are lightweight and take up very little space when empty. I numbered them so that I could track their use.

• 1: used only when I needed to carry more than 2L of unfiltered water from a source. (The more you squeeze them, the sooner they leak, so I didn’t use this pouch often.)
• 2, 3, 4: used in rotation, and only for clean water.

I should have tested each of the pouches beforehand. Number one had a leaky cap, which I replaced with a soda-bottle cap. Problem solved, and all the pouches survived the trail with no further leaks. The only time I needed my full 6L capacity was a two-day stretch between Grants and Pietown.

Before setting out, I measured the filter’s flowrate. Then, having already found the Squeeze’s new flip-top cap to be a bit cumbersome, I replaced it with the old push-pull cap. Finally, I made a stopper for the inlet side of the filter. I used the inline coupling that came with it, and the insert from the end of a disposable ballpoint pen.

But is it safe?

Prior to every back-flush on the CDT, I knocked the filter against a hard surface (a tree-trunk or the edge of the sole of my boot) for 30 seconds. As I mentioned in my first Sawyer-related post, there is a risk of damaging the filter if you hit it too hard or strike it against a surface that’s too hard. Following that post, a Trek reader asked this question.

Did you verify the water quality after performing the hammering? It’s possible that the filtering membrane could get punctured by the debris in the process, and this in part resulted in increased flow.

The only evidence I have that water quality didn’t suffer is circumstantial. During the subsequent 1700 miles where I used the filter from that post (a Sawyer Mini), I didn’t get sick. I knocked the crap out of that filter for the duration of those hikes. I’m happy to report that I didn’t get sick on the CDT either, despite knocking the new filter about for more than 2600 miles.

Sawyer’s website has documentation showing their strength-test summary data and conclusions. Their overall conclusion is shown below. My interpretation is that, of the filters tested, Sawyer’s has the best chance of remaining undamaged as a result of knocking it repeatedly against a tree-trunk.

Putting a stopper on the inlet of the filter may also help reduce the risk of membrane damage. Originally, I made a stopper so that water would stay in the filter while I was knocking it about. I figured that if the water stayed inside the filter, it would slosh around and provide maximum debris displacement. The sloshing may also have a shock-absorbing effect on the membrane, a bit like the fluid-filled damper in a suspension system. That’s just a theory, however.

Filter preparation

After returning from the CDT, I repeatedly gave my Sawyer Squeeze the knock-on-wood treatment. I wanted to clean it as much as possible before proceeding. The problem was, after about two hours, each backflush was still dislodging debris from the filter. When subjected to the same post-hike treatment, the Sawyer Mini produced debris only initially. The rate at which back-flushes were unclogging the Squeeze appeared to be much slower than the Mini.

I moved on to the combined hot-water-plus-knock-on-wood treatment that I mentioned in my second Sawyer-related post. Afterwards, more than six hours later, I recorded the Squeeze’s flowrate. The filter was obviously still very clogged, and I wanted faster progress.

No more syringe back-flushing. Instead, I intended to use the cleaning coupling and a 32 oz. plastic bottle. I widened the Squeeze’s outlet orifice using a sequence of larger drill bits, and then a Dremel. There’s a half-inch airgap between the filter membrane and the outlet, and I was careful not to damage the membrane.

I also wanted to speed up the combined hot-water-plus-knock-on-wood treatment. Not only is the six hours of soak time the most time-consuming part of the process, I guessed it’s also the least effective part. Here’s my condensed procedure.

High-speed-hot-water-plus-Knock-on-wood (HK) treatment

1. Put 16 oz. water in a Pyrex bowl.
2. Microwave the bowl at maximum power until it reaches 140℉. It takes about two minutes – use a thermometer to check.
3. Pour the hot water into the 32 oz. plastic bottle.
4. Attach the plastic bottle to the Squeeze outlet using the cleaning coupling.
5. Backflush the filter with 8 oz. hot water as forcefully as possible. Using slightly more than 8 oz. is OK, but don’t squeeze any air into the filter.
6. Disconnect the filter, insert the inlet stopper, cap the outlet.
7. Pour the remaining hot water into the Pyrex bowl and top it up to 16 oz.
8. Microwave the bowl at maximum power until it reaches 140℉. It takes less than two minutes – use a thermometer to check.
9. While the microwave is reheating the water, give the filter its knock-on-wood treatment.
10. Repeat steps 3 thru 9 as needed. (I did it 18 times.)
11. Backflush the filter with 32 oz. cold water.

Results

The table below shows how long the Sawyer Squeeze took (min:sec) to fill a 24 oz. (0.71L) bottle. I used the average of three measurements and converted the time into gallons-per-minute (1 US gallon = 3.79L). Sawyer Mini results are shown for comparison, and abbreviations are as follows.

• KW = Knock-on-wood treatment described in my first Sawyer-related post.
• HW+KW = Combined hot-water-plus-knock-on-wood treatment, from my second Sawyer-related post.
• HK described above.

• Row 1. The Squeeze is initially twice as fast as the Mini.
• Row 2. Almost two hours of knock-on-wood treatment (approximately 50 back-flushes) restored the filter to 21% of its initial flow.
• Rows 3&4. Row 3 has a six-hour hot water soak. Row 4 has a larger filter-outlet orifice instead. Both treatments contain 18 back-flushes and approximately the same flow-rate improvement.
• Rows 5&6. No significant improvement in flowrate.
• Rows 2 thru 6. During conversion, I added 4% to the Squeeze flow rates. (It allows a more accurate comparison to the final Mini flow rate. More on this in a moment.)

Before widening the Squeeze’s outlet, I performed three syringe back-flushes. On average, I could empty the full 2 oz. (59ml) syringe in 1.8 seconds.

After modification, I did three back-flushes using the cleaning coupling and 32 oz. plastic bottle. On average, I squeezed 8 oz. through the filter in 10 seconds (i.e. 2 oz. in 2.5 seconds).

Conclusions

My initial two hours of knock-on-wood treatment were a waste of time. Previously, the Sawyer Mini quickly reached a state where it produced no more debris. That didn’t happen with the Sawyer Squeeze, not that it matters. It just means that some of the flow improvement was pushed to later rows of the results table.

Don’t modify the Sawyer Squeeze’s outlet. The syringe can generate more back-flush pressure than a 32 oz. plastic bottle (1.8s vs 2.5s).

HK treatment (about 40 minutes duration) is more efficient than HW+KW treatment (about six hours duration). Both treatments produced similar flow improvements, despite my HK back-flushes having lower pressure. The key to flow improvement seems to be:

• Hot water in the filter during knock-on-wood.
• Back-flush with hot water after knock-on-wood.

There are 54 total knock-on-wood treatments in rows 3, 4, and 5 of the results table. If I replace HW+KW with HK, cleaning the Sawyer Squeeze would still take at least two hours. Doing this during a thru-hike seems a little time-consuming. My advice is to start your hike with a brand-new Sawyer Squeeze, knock-on-wood before each back-flush, and back-flush daily. It’ll be down to less than 20% of its original flow by the time you hit 2500 miles, so if you don’t have the patience, plan to replace it.

One final thing. Knock-on-wood is most effective when you hold the filter by its outlet end and knock its inlet end. If you don’t have an inlet stopper, make sure you have the inlet end uppermost. That’ll keep as much water in the filter as possible.

Backflush: Squeeze vs Mini

I previously estimated that I’d filtered no more than 250 gallons (947.5L) using my Sawyer Mini. I backflushed it approximately once per day. During 130 days of use on the CDT, I estimate the Sawyer Squeeze filtered 4% more water: no more than 260 gallons (985.4L). It was also back-flushed an average of once per day. If I assume that I filtered water of similar quality with both filters, I’m ready to compare them.

Looking at this chart, I see that it’s time to throw out my Sawyer Squeeze. After 260 gallons, its flow rate is slightly higher than the Mini. After 320 gallons, it’ll be worse than the Mini.

Previously, I guessed I’d be throwing my Sawyer Mini away after 600 gallons. It might actually last for 800 gallons. Or maybe not. At this point, I’m a little tired of beating the crap out of filters – I think I’ll just buy a new one.