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Curiosity 8 – Water filters/treatments?

At the Philmont Scout Ranch they have crews treat the water.  They give you Katadyn Micropur tablets for water treatment.  I also thought it was interesting that Outdoor Gear Lab did not have the Katadyn Micropur tablets in its review (titled/dated, best of 2021).

I have seen a number of VLOGs using a Sawyer mini or Squeeze.  Usually, it seems folks choose the Squeeze Mini.  I have a Sawyer Squeeze (not the Mini) as the flow rate is better than the Mini.

And some chemical treatment options don’t handle Giardia or Crypto (or take a while to handle those protozoa; I think that is correct for these).  Also, a lot of filter/treatment options do not handle chemicals.

Of course, there is always boiling.  The number I have seen is at least 3 minutes (after bringing the water to a rolling boil; continue to boil for those number of minutes).  I usually look at 5 minutes as five is an easy number to remember.

There are so many options out there.  Of course, there is always boiling.

So, curious what folks know/think about water filters/treatments.

  • Do you understand the items that different filter/treatment systems filter or treat (i.e., protozoa, bacteria, viruses, chemicals)?
  • Do you filter or treat the water?
  • Do you use a treatment (i.e., chemicals or tablets)?
    • Which do you use?
    • And which type (I.e., Chlorine Dioxide)?
  • Do you use a filter?
    • What type (i.e., gravity, squeeze or pump)?
    • What do you think about Sawyer Squeeze or Mini?
    • What do you think about the MSR Guardian (pump)?
      • Noted this one specifically as it handles more items than most pump filters.
    • What about gravity systems (i.e., Platypus GravityWorks)?
  • What about other filtration/treatment (i.e., LifeStraw or Ultraviolet).
  • Do you use something different if in a group?


19 Replies

Yes I always filter water when backpacking. I use a Sawyer Squeeze with a CNOC bags set up for gravity (because I am too lazy to squeeze and the Sawyer bags suck) and I store water in PET /PETE SMART Water or similar disposable bottles.  (I would consider Nalgene wide mouth polythene bottles for winter.)  This setup is effective against particles, protozoa (eg crypto, giardia), bacteria and some larger viruses although probably not the ones you might care about.  Sawyer Squeeze filters use 0.1 "absolute" micron pore size where others are typically 0.2 micron with no given size variation although the difference is probably of no practical importance.   Water borne viruses are not a big problem in US backcountry water but you might be concerned at over used campsites or water used by stock.  The main disadvantage of this kind of filter you must be careful not to let the filter freeze. Sawyer, in particular does not guaranteed it to work if you allow this to happens...always keep it in a zip lock in your sleeping bag at night.  Sawyer does not say it will stop working either so if you freeze your filter I would still use the filter if only to remove particles.  Use a secondary method also, most of which work best with clear water.  Just replace the filter as your earliest opportunity

I also carry Chlorine Dioxide  (Katadyn tabs, Aquamira tabs or drops) as a backup and if I suspect the water source (viruses).  I have only used these when I forgot to clean and dry my filter over the winter and the water can through tasting like dirt on my first trip the following year.  That didn't really fix the problem so I flushed it with household chlorine bleach when I got home (see instructions) which did. 

I have bought another kind of tab (Aquatabs) which kills viruses, bacteria and some protozoa but does not work for crypto.  They will work as a adjunct to a filter that will remove crypto.  I don't really recommend these although Chlorine Dioxide takes 4 hours to be guaranteed to kill crytpo and you have use a rolling boil for 1 min or 3 mins above 6500 so using an appropriate filter is preferred anyway.

I don't use or recommend iodine...taste and bad effects from prolonged use and not very effective against giardia and not effective against crypto. 

I generally carry a stove and pot which could act as a backup if I compromised the filter but I have never felt the need to do this.

I used to use a Katadyn Hiker filter (particles, protozoa, bacteria, some viruses, some chemicals) which is better for more dubious water because the filter has an active carbon element...compared to the Sawyer it is relatively heavy, the active carbon gets consumed and the replacement filters are expensive.  I might chose to used this in some areas where stock and agricultural run off can be a concerns.

I briefly used a Playpus gravity system but had a bad experience with the filter element clogging immediately so haven't used it since.  I did get a new element for it but its is relegated to "emergency" use.  It is really oriented for group use which can make sense when primitive camping but for backpacking these days I recommend everyone to carry their own filter since filters are much lighter and it guarantees a backup in a group.

I have considered getting a BeFree for day hiking or overnight trips since it is a little more convenient for occasional used if less flexible.

For international travel I would consider a UV Steripen since this allows for quick and discrete purification of clear water in many travel situations.  Clear water required, fragility and batteries make it less idea for backpacking in the US although the rechargeable one might be a good backup to a filter, particularly if you don't carry a stove.

You should always inquire about local water conditions.  One concern is the increased incidence of toxic algae mats that produce a toxin that cannot be boiled, filtered or treated in any portable way.   Some lower areas of the Sierras (eg Tenaya canyon in Yosemite and the Merced river to the west of Yosemite) have been affected due to drought conditions. 


Hi @OldGuyot .

As always, a very thorough and well thought response.  I have to agree with @Philreedshikes in his admiration for you and the knowledge you bring to the forum.

I have a question for you.  I have a lot of confidence in all of the filter and treatent systems you mention when used in more remote, wilderness areas, where the source of contamination would be biological in nature.  But, what about in more populous areas with nearby roadways and bridges?  Would you think there's a significant enough amount of chemical runoff (gas, diesel, oil, antifreeze) that would render the water not potable, even with filtering/treatment?

I tend to think that if fish, frogs, plants, etc, are thriving, then the chemical contamination is negligible, and I've never gotten (knowingly) sick when filtering water near roadways, but...

What are your thoughts on this?


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@Rob6 I have no particular expertise in water purification beyond published information but this is my understanding...

Drinking minor chemical pollution long term will possibly shorten your life and provide you with a more miserable death than might otherwise be the case and/or trigger some long term debilitating ailment but a one time use is unlikely to shorten your current trip provided you filter out the critters and it is clear and palatable.  Avoiding dehydration and heat stroke is far more important. 

However, I would not choose to use a water source that follows close to a busy road unless it was the only choice and the alternative was risking severe dehydration.  Roads anywhere usually indicate some past or present commercial use which often brings with it the possibility of chemical contamination.  It is best to apply some judgement to minimize the chance of drinking water from mine tailing, agricultural or highway run off.  Similarly, streams and rivers that travel through built up, developed, dilapidated and "industrial" areas including agribusiness will tend to contain more pollutants from storm drains and runoff etc. so they are best avoided as water sources out of choice. Larger rivers have traveled further and so have more chance of picking stuff up along the way so even in the back country smaller local streams are probably preferable.  There is no hard rule and local knowledge, if you can get it, is the best guide.

As a general rule amphibians are supposed to be a good indicator of healthy water since they are supposed to be more sensitive to pollutants.  Probably such a source is a good bet unless the frogs have two heads.

Thanks @OldGuyot , and @hikermor for confirming my suspicions and concerns regarding chemical pollutants and runoff from roadways and storm drains.  It's nice to know I'm not off my rocker, or being overly paranoid.  Considering my location in the Mid-Atlantic, those are real concerns.  As always, I'll continue to carry more than enough water for my local day-hikes and car-camping trips and save the water treatment options for my adventures in the backcountry.

Superusers do not speak on behalf of REI and may have received
one or more gifts or other benefits from the co-op.

I have the Sawyer Squeeze (as i noted).  So far, I have not had an issue with the Sawyer bags (2 1L bags).  I have seen some VLOGs and other notes, as you also also noted, that there are issues with the Sawyer bags and they have gone to the CNOC bags which work with the Squeeze or Mini filter.  CNOC also has their own filter and squeezable bottles that work with their filter or the Sawyer filter.

I wonder about Sawyer's S3 filter for the Algae?



@JohnL02 As far as I have found, reverse osmosis is the only effective way to filter cyanotoxins from blue algae. Generally this type of filter is fairly large suitable for under sink installation up to industrial scale.

I don't know Sawyers S series (S1, S2, S3) will "filter out"/"absorb"  cyanotoxins.  A question for Sawyer I think. Technically these are a type of biological "hydrocarbon" having a similar structure to proteins so it is possible they are "absorbed" in the same way as viruses.  It would be interesting to know if the S series absorb prions also although the incidence of those should be much less common.

Generally, cyanotoxins apart,  the S series are overkill and not that convenient for backpacking in the US but might be a good international or emergency preparedness option where you may need to rely temporarily on a compromised urban water supply.

The S series claim virus(S1,2,3), hydrocarbons(S2,3) and heavy metal(S3) protection.  They basically uses a standard 0.1 micron Sawyer Micro (particulates, bacteria and protozoa) on top of a disposable squeeze bottle that contains an absorption foam which does the rest.  The absorption foam acts in a similar way to an activated carbon filter with the same issue of limited life.  The effectiveness of carbon filters depends on the form of carbon used and my guess is these S filters are essentially activated carbon based but the foam presents it in a particularly effective way with S1 through S3 increasing the amount of available activated carbon...but that is a guess.  There may be more cleverness.  I don't know if they are more effective than other filters with carbon elements but the protection claims seems more assured.

A problem I see is that the absorption foam is in the bottle so probably you should not use cloudy water that will overwhelm the carbon and prematurely clog the Micro which is not noted for maintaining a good flow rate.


Agreed.  I thought the S series was interesting in what was listed.   And the sponge material is what does some of the work.



@JohnL02The main problem with the Sawyer "squeeze" bags is that they are hard to fill making the system as sold inconvenient to use.   The bags have a small opening and no significant 3 dimensional structure so you can only effectively fill them directly under a faucet or falling water which is fairly limiting in the backcountry.  You can use a separate scoop but meh! 

A secondary problem is that there are numerous reports of the bags splitting when being squeezed.  I suspect this is not quite as common as these reports might lead us to believe but along with the first issue it is not a good look. 

The CNOC bladder solves these issues assuming you don't just use SMART water bottles with a Squeeze.

What makes the Sawyer Squeeze a popular filter apart from being light and inexpensive (compared to the previously popular pumps) is that its threads work with many disposable water bottles, SMART water being a particular popular variety to use.  This makes it very flexible for longer term use on the trail (eg thru hiking)

The Sawyer mini also works that way although it reportedly has flow issues over time making it less desirable.  The thread on the Sawyer Micro is slightly different making it frustrating to use with SMART bottles because it tends to push the washer into the bottle opening.  The Micro also reportedly has flow issues over time. 

Something to note is that Sawyer hollow fiber filters must be back flushed regularly (after each use is best)  and should be thoroughly backflushed, disinfected and treated with vinegar (see instructions) between trips or before long term storage (or you can treat them as "disposable").  Other filters cannot be backflushed (eg BeFree), only cleaned.  Another tip is to always carry a spare washer since the Squeeze does not work well without one and they do occasionally fall out and get lost.  A standard garden hose pipe washer from any hardware store will work in a pinch although you may prefer to use washers intended for drinking water like the ones supplied.  Personally I used with with a stainless steel filter mesh to prevent larger particles from getting in.

As to the Sawyer bags, some advocate just throwing them away but they can make good lightweight compact secondary storage bags in case you have a long water carry.  I generally carry at least one flat bottle for that purpose...mostly to provide flexibility if I wanted to dry camp...although so far I  have not followed through on that.  Another use for carrying a flat bottle is for drink mixes since, when empty you can easily put it in a bear canister or hang to protect the bears from the fruity smells that these drink mixes can have.  Drinking from a floppy flat bottle while moving is a bit of a trick.  There are always tradeoffs to make.

The Hydroblu Versa is not a CNOC product. They just retail it.  CNOC also sell Katadyn BeFree cartridges.  The Hydroblu Versa hollow fiber filter cartridge is interesting in that there is an available add on/replaceable carbon element (not sold by CNOC) which is fairly inexpensive.  The annoying thing about the Hydroblu though is that it specifically states that it does not work with SMART water bottles on the squeeze end...The thread leaks under pressure apparently (might be fixable with an additional washer).  I think they do work with common soda bottles but I like the SMART shape.  

Thanks @OldGuyot.

I can see the hard to fill issue.  I was gathering that the splitting was a bid deal but wasn't sure how big.  We had to use my (and two other folks) Sawyer Squeeze at Philmont.  One of the mornings our crew realized that we did not have enough Katadyn Micropur tablets to treat the water.  Luckily, we had the 3 Squeezes and their 6 1L bags as well as another person had a 2L bag (all the Sawyer bags).  We used them quite heavily that morning to treat the water for our crew 14 members.  I also took extra water that morning and drank from my Squeeze.  The one thing that we did have fun with that I don't think anyone mentioned is that screwing the Squeeze on and off (maybe because of doing it that much and quickly) we had issues with the rubberlike washer coming out of the Squeeze (may Sawyer has changed that by now).

I like the CNOC bag like my hydration bladder it has a wide opening although the fill with those can still be a bit fun if you don't have room in the water to tilt them or hold them more upright.  Everything has it pros and cons.

I may have to see if my Squeeze still works as it has been stored since that Philmont trip in 2017.