Thursday, February 16, 2012

Gravity/Squeeze Filtration/Purification System

One Kit.  Multiple Uses.  Adaptation.

Ok, so I've seen so many videos on backcountry cook kits (and eventually I may post mine!), but very few on water treatment comparatively.  Water treatment is very important to me, and, like everything else, there isn't a "one right way" to accomplish it.  Some are concerned only with disinfection, others with removing particulate, many both. Others yet would like to also remove odors from the water.  I spent several years using the MSR Miniworks filter which uses a ceramic filter (0.2 micron), and a pumping style filtration system.  Many people have good luck with that filter, I did not (leakage around the pump head seal).  Also, it's a very heavy system (16oz dry) compared to some of the more recent designs, and the thought of replacing it lead me to explore the many options out there.

What to think about:
How much stuff do you want to take out?  Filters are available in 3micron (Frontier Pro), 0.1 micron (Sawyer Squeeze), .02 micron (Sawyer Point Zero Two system), and many areas in between.  What kind of "stuff" are you talking about?  If you're talking about protozoa (crypto, giardia), 1 micron should remove them.  If its bacteria (fecal coliform, etc.), 0.1 gets all of them.  Viruses require 0.02 or less. If all that you want to remove is detectable particulate, the 1-20 micron size (filter bag, coffee filter, denim, etc) will collect those.  If it's odors and chemical flavor, passing the water through an activated carbon filter post filtration works well.
Why do you want to use filtration to get rid of pathogens?  Some people are quite content with iodine, chlorination treatment (Aquamira), or one of the other misc ways using chemical salts (MSR MiOX) to disinfect their water.  Others use UV irradiation (Steripen) for disinfection.  Each of these are effective to varying degrees and have certain drawbacks.  Chlorine, for example, is not considered effective in the removal of protozoa in  periods of short term exposure.  UV treatment effectiveness is also proportional to exposure time and can be aided if particulates are not present that would block the UV rays.

Here's the rub: Its up to you, BUT don't carry something that's needlessly redundant, unnecessarily heavy, or doesn't suit all of your needs in water treatment.  Carrying UV, Chlorination, and micronic filtration equipment is completely unnecessary (wearing a belt and suspenders is ridiculous).  One degree of redundancy is really all you want to do.  For example. A 1 micron bag filter will remove protozoa and particulates, and a UV pen will get rid of what's left.

What I've put together:
That all said, here's what I do.  The Sawyer Squeeze is versatile, light enough, and filters down to a level that will remove bacteria.  I'm not concerned about viruses for the hiking that I do, but if I were to go to an area where waterborne viruses were an issue, I would bring chlorination tablets.  This filter lets me filter water in various ways that suit my needs.  For example:  I don't carry a water bottle typically, opting instead to use a bladder inside my pack with a tube. The Sawyer filter coupled with some adapters including the Hydrolock kit from Camelbak allows me never to have to remove my bladder from deep inside my pack where I keep it.  I can't tell you how many times I've arrived at a water source, had to get out all of my filtration equipment, dig the bladder out of my bag, and then repack everything once I'm finished.  Adding to that frustration from mishaps related to not hitting the opening of the bladder which results in a wet hydration bladder going back into the pack.  Not anymore!  The filtered water is pressure fed right back down the outlet pipe, and the size of my bladder (2L Platypus) is equivalent to two fillings of the 1L dirty bag that comes with the Squeeze system.  Water goes from source to storage without hitting a drop of air, or encountering any point of outside contamination.

Although my goals seem to be a little different, I put my kit together in a manor similar to the one shown in a post on White Blaze forum. Like the poster there, I separate these things into "clean" and "dirty" categories to avoid contamination, but I consider the filter itself "Clean" provided that you plug the dirty end after use.  If residual dirty water from the inlet end of the filter comes into contact with the outlet end of the discharge hose, then what's the point of filtering in the first place?  Freezer bags are good for this.  The filter inlet end gets plugged and the whole thing gets stuffed into a bag with the outlet hose and adapters which then go inside the container.  The dirty scoop and funnel serve as the protective container for everything and holds the other dirty items loose inside.  The container itself, including the funnel, is made from a cut down rubbing alcohol bottle.  Initially, I made the adapters using soda bottle caps and the threaded mouths epoxied together to suit the purpose.  I've also tried using a Tornado Tube.  However, the threads don't match up perfectly with the threaded ends of the Squeeze (Pepsi or Coke both seem to have a bit of a thread pitch difference).  After using the rubbing alcohol bottle, I realized that the cap and mouth of that bottle matches up PERFECTLY with the Sawyer system.  In fact, I may have accidentally switched the caps to the squeeze bladders and can't tell the difference now.  The problem is that there isn't a flange on the alcohol bottles in the same way that there is on a soda bottle so gluing male adapter components together becomes a bit of a problem.  Creativity and patience solves this.  Also, the Aqua Simple connector purchased from Arrowhead Equipment is not able to thread down far enough on the Squeeze to form the necessary seal, so a female-male adapter is needed on the outlet side of the filter to connect that fitting.  It leaks profusely if you skip this step, and I'm not worried about the 8 grams.  The problem becomes color designation between clean and dirty fittings, but a sharpie handles that task well (soda bottle caps would have been perfect for this).

Filter (naked and dry):
Funnel/container lid:
Scoop/container body:
Female-Female Adapter:
Particulate filter:
Dirty 1L bag:

Female-Male Adapter:
Tubing Adapter w/ 5" tubing and Quicklock fitting:
End Plug:

I wrote earlier about redundancy.  The kit as pictured below relies solely on filtration to remove contaminants.  It would not be out of the question to add chlorine tablets or drops or iodine to this kit for further disinfection.  A UV device would do provide the same redundancy.  All would provide a slight weight and cost penalty that is up to the individual to consider how severe they consider that penalty.

Making the adapters:
Caps from rubbing alcohol bottles have identical threads to the sawyer bags.  Ideal for making an adapter.  The threaded part is the cut off portion of the same rubbing alcohol container.

Clamp it and let it cure.

This epoxy DOES NOT WORK!  As it cures, it becomes less resistant to the twisting motions that are going to be very common on any of the pieces used in this kit as they are screwed on and off of the filter.  Dr. Bond Plastic adhesive doesn't work either for the same reason.  Good old Loc Tite Superglue or Gorilla Superglue seems to work well. 
Whats in the Kit?

Dirty stuff.  The alcohol bottle is cut down to size and can be used as a scoop.  The top of the bottle can be connected using the red female-female adapter (made with soda caps) and used as a funnel to get water into the bag.  This works nicely with the 1micron particulate filters made from filter bags used in biodiesel filtering.  The 1L Sawyer bag is the dirty bag.

Clean stuff.  Obviously the filter itself is pictured.  In addition to that isthe end cap (green soda bottle parts) which keeps the dirty water from leaking out and contaminating the other clean stuff when stored.  Also pictured here are the fittings necessary to connect the filter to the hydration tube leading to my in pack Platy bag.  The white female-female adapter is used for backflushing.

Funnel affixed to the top of the dirty bag ready and ready to fill.

Backflush mode.  Simply squeeze clean water back through the filter.  The syringe is intended for this purpose, but I leave that at home and backflush using this method when need be (not often).

Everything fits into the scoop bottle.  Dirty stuff loose in the bottle, clean stuff bagged up in a freezer bag.  There's certainly enough room to throw in a little baggie of chlorine tabs if one were so inclined.

203g isn't bad!  It's approx 7oz which is less than half the weight of my old Miniworks setup and is WAY more functional.  Add to that weight the weight of a lightweight stuff sack, the sport top adapter that came with the filter (not pictured as i don't usually use it), the particulate filter (not pictured, currently replacing mine!), and chlorine tabs and you're still under 8oz.  By no means "Ultralight," but this is a durable, long lasting, very serviceable, setup.

Closing Remarks:
I am open to finding ways to further reduce the weight of this system without compromising the functionality.  I think some savings could come from using a different bottle for the container.  These alcohol bottles actually are not available anymore, now a square bottle is used which contains substantially less plastic and thus weighs less.  I enjoy the built in funnel/scoop, which are very necessary for shallow water collection.  I could also scrounge a couple grams by using the .5L Sawyer bag that came with the Squeeze filter, however right now I feel that it's the perfect size.  The other advantage of using the 1L bag is that I can fill the 2L Platy and reserve 1L of dirty water for later filtration if the next water source is a ways away, allowing for 3L total water carrying capacity.

Another thing that you may want to consider is storage.  Damp gear leads to mold and mildew.  Storing this kit in a way that will allow it to fully dry out seems like a good idea.  I like to remove the end plug and cap from the filter itself for storage, and allow all of the bags to fully air out before putting them back in the gear locker.

Like always, comments are more than welcome!

After reevaluating this kit having made a write up on it, I think I'm going to try to make the clean side female male adapter out of a soda bottle threaded portion and an alcohol bottle cap.  The flange and thread depth are just of better sizing for the job and my capsules hold up way better than my adapter does.  Limiting the number of times that I disassemble the hosing fitting from the adapter has kept me going for a series of uses, but I just heard it cracking again like it did with the Dr. Bond Plastic Weld...  time for a new strategy!


  1. I just purchased the Sawyer Squeeze filter and like your ideas. Where did you get the cap/hose connector that connects to the clean end of the filter?




      A word of warning with that cap though. The barb piece is designed to swivel in the cap piece however it lacks a gasket to keep it sealed. The way that it accomplishes the seal is by press fitting into a smaller opening. The threads on the cap piece are too long to thread onto the short threads of the Squeeze, so that adapter that I built is necessary unfortunately. On the bright side, soda/rubbing alcohol bottle caps do a good job at that as long as you can keep them glued.

      I've looked into other fittings like these ( but would need to know the correct thread pitch, which I don't.

      The other problem is that the barb size on the cap is different than the barb size on the Hydrolock kit from Camelbak. Not a big deal though if you warm the tubing in hot water before fitting it to the cap adapter.

  2. Been looking into getting the Sawyer Squeeze Filter and just came across your blog. Good ideas. Awesome work man.

  3. Great write-up, I am a big believer in commenting on blogs to inform the blog writers know that they’ve added something worthwhile to the world wide web!..