Friday, September 14, 2012

Sawyer Squeeze Filter: a Review

Over the years I have mostly used either iodine or Aquamira to treat water in the back country, mostly because they were lightweight and fairly easy to use.  But I was intrigued by the Sawyer Squeeze filter, mostly because of its weight, but also because  it appeared to be fairly simple to use.  So I bought one and have used it for over 500 miles this year.  The following is a review of the filter, along with some tips for using it.

The filter itself is fairly small, weighing in at 3 3/8 oz or 96 grams, is just a shade under 6" long (with the optional cap included) and a bit under 2" in diameter at its widest.  Sawyer claims that the filter removes anything larger than .1 micron, including 99.99999% of bacteria, including Salmonella, Cholera and E. Coli, and 99.9999% of protozoa, including Cryptosporidium and Giardia.  The filter does not remove viruses however.

Unfiltered water goes into one end of the filter, through the side walls of a bunch of micro-fibrous tubes into their center, and then out the other end of the filter as clean water.  A certain amount of pressure is required to do this, provided either by gravity, or by squeezing an attached bag of untreated water.  Either way will work, although the squeezing method will generally be faster.

The filter comes out of the box with 3 squeeze bags, one each of 16, 32 and 64 oz.  You can also use a regular soda bottle or other water bottles with compatible threads.  My Platypus bottle has the correct thread size, although apparently some do not, so you would want to check that before going out on the trail with one.  The Mylar bags that come with the filter are probably the lightest option and can be bought separately, so that is probably the best option.

The most general way to use the Squeeze is to fill a bag, attach it to the filter, aim the discharge into your water bottle, and then squeeze the bag; out comes clean water.  This operation is generally fairly simple and within a couple minutes of stopping you can be drinking fresh filtered water.  The biggest challenge I have encountered with this is getting the bag filled.  It you have dripping, or cascading, water this is not a problem.  But it can be difficult from a lake or smoothly flowing river or stream.  When you put the bag into the water to fill it, the water pressure outside the bag keeps it collapsed and very little water will go into the bag.  I resolved this by cutting the top off of a soda bottle and use it as a scoop to pour water into the bag.  This works especially well when the water source is shallow, especially with a lot of sediment.  It is easy to skim water from the surface without disturbing the stuff on the bottom.

I would caution against squeezing the bag too hard.  I have heard from lots of folks who manage to bust the seams of the bag, I suspect because they clamp down too hard.  I apply gentle pressure to the bag, neatly rolling it up as it empties.  This keeps the seams laying flat all the time, reducing the chance of them popping open.  It also makes it easier to get all of the water squeezed out of the bag.  With a filled 2 liter bag, I can fill both of my quart Gatorade bottles in just a couple of minutes.

But what happens if you do manage to bust open your squeeze bag?  You could always carry a spare bag.  But if you have a soda bottle top for a scoop like I do, you can screw the top onto the input side of the filter and then use it as a gravity filter.  My scoop is about 4 inches long and, so long as I keep it nearly full, will allow me to fill a quart Gatorade bottle in about 7 1/2 minutes.  That is slow, but easy, and does give you a fall back without having to carry an extra bag.

I have also, for long dry stretches, carried the squeeze bag full of water, and then filtered it as needed when my Gatorade bottles ran dry.  You need to be a bit careful when doing this, ensuring you have the cap on good and you don't unduly stress the bag, otherwise you might have a mess.  I carry the full bag in the outside mesh pocket of my ULA pack, cap up, and have had no problems with doing so.

When not in use, I carry the bag rolled up and tucked into the soda bottle scoop along with the filter.  I have taken the remainder of the soda bottle and notched it.  It then fits over the other side of the bag and filter with the bag cap sticking out the notch, offering additional protection for the bag while tucked into the outer mesh pocket of my pack.  And then the whole thing is stuffed into a gallon Ziploc bag, holding it all together.  The filter, a 2 liter bag, the cut-up 20 oz soda bottle and the gallon Ziploc bag weigh a total of 167 grams, or 5 7/8 ozs.

I really like this filter, especially once I figured out how to use it effectively.  I have had no problems with it this year and look forward to using it for years to come.  Keep it periodically back flushed, be gentle with it, and you should be happy with it as well.
For emergency use, the soda bottle scoop can be attached to the filter  input.  If the scoop is kept filled it will take about 7.5 minutes to fill the quart Gatorade bottle.

This is my filter kit: the filter, a 2 liter bag, a cut up soda bottle and a gallon zip lock bag.

The filter and bag go into the soda bottle with the bag cap sticking out of the  notch in the bottom of the soda bottle.

And then the whole thing nestles down into a gallon Ziploc.  




4 comments:

  1. I used plastic grocery bag as a gravity feed hanger with this set-up. Works great with the 64 oz bag. Double bag it and cut a small hole in center bottom big enough for filter. Use bag handles to hang. The Mesh bag the box offers is not available yet, I checked with Sawyer. By draging the 64 bag through the lake water I could get about 2/3 full.

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    1. Good idea. I have several mesh bags that melons come in. I bet they would work even better than the plastic bags.

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