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Reviews > Water Treatment > Filters > Sawyer S3 Select Water Purifier > Test Report by Brian Hartman

October 6, 2021


NAME:Brian Hartman
EMAIL:bhart1426ATyahooDOT com
LOCATION:Westfield, Indiana
HEIGHT:5' 9" (1.75 m)
WEIGHT:160 lb (72.6 kg)

I have been backpacking for over 20 years throughout Indiana, Ohio, Kentucky and most recently in the Western USA. In addition to backpacking I enjoy family camping with my wife and kids and being outdoors in general. I would describe myself as a mid-weight backpacker. I hike with fairly light weight clothing, equipment, and gear but still like to bring more than the bare essentials with me while on the trail.




Manufacturer: Sawyer Products
Year of Manufacture: 2021
Manufacturer's Website:

Item tested: Sawyer S3 Select Water Purifier
MSRP: $79.99
Listed weight: 0.625 lb (283.5 g)
Measured weight: Bottle 0.481 lb (218.3 g); bottle plus Micro Filter 0.600 lb (272.2 g);
bottle plus Micro Filter, syringe, and blue adapter 0.669 lb (303.3 g)
Liquid volume: 20 oz (591.5 ml)
Listed dimensions: 14 x 8.5 x 3 in (35.5 x 21.6 x 7.6 cm)
Measured dimensions: 10.75 x 2.5 x 2.5 in (27.3 x 6.4 x 6.4 cm) for the bottle and 4.25 in (10.8 cm) tall with 1.5 in (3.8 cm) diameter for the Micro Filter
Filter Material: 0.1 Micron Absolute Sawyer Micro Squeeze Filter
Longevity: 400 uses
Removes: Heavy metals, viruses, bacteria, protozoa, chemicals, pesticides
Color: Orange

The Select S3 is a dual stage water purifier that consists of a silicone bottle with foam inside and a Micro Squeeze Filter on top to remove pathogens, sediment, particulates, and microplastics.   

Purifies water in just 10 seconds
Reduces contaminant levels to below EPA standards for safe, clean drinking water

Ideal for hiking, camping, scouting, domestic and international travel, natural disasters, hunting, survival, and emergency preparedness


The Sawyer Select S3 (hereafter called S3 or water purifier) is made by Sawyer Products in Safety Harbor, Florida.  Sawyer is best known for their #1 selling Sawyer Mini, the filter of choice for many hikers on the AT (Appalachian Trail) and PCT (Pacific Coast Trail), but they also make sunscreen and insect repellent, something I didn't know.  The S3 uses a foam purifier, located in the orange silicone bottle shown above and below, to absorb and remove chemicals, pesticides, heavy metals, 99.99% of viruses; and a Micro Squeeze Filter, shown in black, to remove standard pathogens, sediment, particulate, and microplastics.  The foam membrane also reduces heavy metals like copper, arsenic, and mercury down to 0.5 parts per billion.  Together, the S3 purifier and filter provide unrivaled protection when hiking in the USA, and peace of mind when traveling outside the USA, where the risk of water contamination, even in tap water, can be much higher.

The bottle has a black lid which should not be removed since it can leak if not resealed properly, and a white cap which gets removed to fill the bottle with water.  The process for purifying water is simple, fill the bottle with water, screw on the Micro Squeeze Filter, squeeze the bottle with alternating motions for 10 seconds, and then drink.  The Micro Filter has a push-pull cap for easy drinking directly from the spout, or the purified water can be squeezed into another container.  Cleaning the Micro Squeeze Filter, to prevent it from getting clogged, is as simple as forcing water through it in the opposite direction it normally travels.  This is done using the syringe and the blue adapter.  Cleaning / backwashing should be performed on a regular basis depending on how dirty the water is that's being filtered.  When flow rate starts to decrease that's a good sign it's time to backwash.  The filter should also be backwashed before and after long term storage.  On a final note, the bottle holds approximately 20 oz (591.5 ml) of water and is rated for up to 400 uses.  Sawyer sells replacement bottles as needed.  

According to the manufacturer, the bottle can be stored long-term with either the Micro Squeeze filter or white cap screwed on top of the bottle and proprietary ingredients in the foam make sure bacteria doesn't grow on it.  However, I found information on Sawyer's website that says they recommend storing the Select system filled with water, preferably distilled or non-chlorinated water.  Also of note, the bottle should not be compressed for extended periods, or it will shorten its life.  The bottle can also be dried out before storage by simply placing it in a dry area with the lid removed so that moisture can evaporate out.  Once the bottle and foam are dried out, they will produce less water than normal for their first few uses since the foam holds onto some of the water.  Finally, Sawyer says that the filter should not be allowed to freeze as that may harm it.  Their recommendation is to replace the filter if it freezes.

a7   a8   a9


Filling the bottle through its 0.75 in (1.9 cm) opening was a slow process that took several minutes, but I'm hoping subsequent fillings go quicker now that the foam is conditioned.  I'll continue to monitor this during Field Testing and report back on my experience.  Squeezing the bottle to move the water through the foam was easy to do, requiring little effort, and the flow rate of water through the Micro Squeeze filter seemed fine at least for my first try. 


The Sawyer S3 water purifier appears to be well designed, well built, and well tested, and I look forward to using it during the next two months of Field Testing.  Please stop back then to read my review.  In the meantime, this concludes my Initial Report for the S3.




During Field Testing I took the Sawyer S3 on a 12-day backpacking adventure to the Southwest USA where I visited Zion National Park UT, Mohave National Preserve CA, Joshua Tree CA, and Death Valley CA.  I planned to hike the Sequoia National Forest too, but the park was closed due to forest fires.  Temperatures during my trip ranged from 29 to 74 F (-1.7 to 23 C) and skies were clear to partly cloudy with no hint of rain.  In fact, it was cool, dry, and windy most days. I hiked approximately 96 miles (154 km) on this outing at elevations ranging from -282 to 5,790 ft (-86 to 1,765 m).  The landscape was incredibly varied from park to park and the scenery was breathtaking, but water was scarce outside of Zion.  To that end, I collected and filtered water from the campgrounds while in the Mohave NP and Joshua Tree.    


Throughout testing I carried the S3 on the outside of my backpack in one of two mesh water bottle pockets.  I carried a 32 oz (0.95 l) Nalgene bottle in the other pocket and used it to store purified water I squeezed from the S3.  The S3 was sometimes challenging to use, but it did a good job purifying water and proved durable and leakproof.  

Fit: Being narrow, at 2.5 x 2.5 in (6.4 x 6.4 cm), and tall, the S3 fit loosely in my backpack's mesh pockets and tended to fall out when not strapped in.  Although lashing the S3 to my pack was inconvenient, I rarely drank directly from it, so not being able to remove it while wearing my pack was not a problem.  When I needed a drink on the go I simply reached for my Nalgene bottle.

Ease of Use: The narrow opening on top of the S3 made it challenging to fill at times.  I found it most difficult when the water source was shallow and stagnant because I couldn't submerge the bottle and/or take advantage of flowing water to help fill it.  Squeezing the bottle, then quickly dunking it underwater proved the quickest way to fill it.  Otherwise filling the bottle in shallow water took more than several minutes.  Squeezing the bottle, to move water through the foam to purify it, was easy to do.  And finally, squeezing water from the S3 through the Micro Squeeze Filter and into my Nalgene bottle took some effort and sometimes significant time depending how clogged the Micro filter was.  Every few days I found it necessary to backwash the Micro filter to restore its flow rate.  Having to backwash the filter so often didn't seem right, but it made a significant difference in water flow.

Durability: The Sawyer S3 proved durable on my trip out West.  Although it fell out of my backpack several times before I strapped it down, it never broke.  I suppose the black cap could've cracked if it landed on a rock or concrete but luckily it didn't.  The silicone bottle was tough and flexible so I never worried about it getting damaged.  

Leak proofness:  During my trip I didn't have any problems with water leaking from the S3 bottle or the black cap.  When temperature were below freezing in Zion I squeezed as much water out of the S3 as possible in between fillings, but a safer choice would have been to store the bottle in my backpack.  

A4    A5     A6


The Sawyer S3 was effective at filtering water, durable, and leakproof, but it was also sometimes time consuming and temperamental.  

This concludes this Field Report.  Thanks to Sawyer Products and for allowing me to test the S3 water purifier.

Read more reviews of Sawyer Products gear
Read more gear reviews by Brian Hartman

Reviews > Water Treatment > Filters > Sawyer S3 Select Water Purifier > Test Report by Brian Hartman

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