Most efficient gravity filter system – need market update

Re-use of other parts — should be the same in all cases. All we are discussing is which filter to put in the middle of things.

One advantage to the MSR and CleanStream filters may be that they claim a 50% greater flow rate than the Sawyer. That could be due to being 0.2 micron, while Sawyer is 0.1 micron? It also may not matter all that much in a gravity setup, since you are doing camp shores while it flows, anyway. But how about if you use it along the trail?

Length of tube — I keep seeing people refer to a long length of tube from the dirty bag to the filter as making things go faster. That is not literally true.

What is true is that the difference in height between the top surface of the water in the dirty bag and the top of the filter is what controls the pressure, and therefore the flow rate. What is at issue is the weight of the water column.

To the extent that "long tube" means "hang the dirty bag higher above the filter, then yes it does help the flow rate. Not trying to be pedantic — just trying to ensure no one misunderstands. Long tube will not help you, unless you use it to hang the dirty water higher above the filter.

— MV

I know this is an old post, but thought I'd share my experiences.

I have the Sawyer Water Purification Kit from Walmart. It's the .02 Micron size that filters out viruses.

Longer tubes definitely do increase the flow rate, though not by much from what I can tell. The improvement works whether the longer tube is before or after the filter. What's important is the height of the water column both above and below the filter.

I think the longer tube after the filter works because it's acting as a syphon.

Now of course if you stick a 20' tube after the filter and leave it rolled up in a pile on the ground, that's not going to help. It's the vertical distance (not necessarily the tube length) between the top of the water in the dirty water container and where the water exits the output tube that's important.

I'm not personally a fan of the Platypus reservoirs, especially as a dirty bag. And the big zip is almost as heavy as the bag I use, but my bag is tougher. So I run it like this:
1. Dirty Bag: 4-liter MSR Dromedary bag with the bottle cap that came with the Swiftwater. The cap has a built-in nipple to attach tubing. The Dromedary bag has grommets that work great to tie it to stuff.
2. Hose to the Swiftwater.
3. Hose to a Katadyn carbon filter.
4. Clean Bag: The Katadyn carbon filter plugs into a 3-liter MSR Hydromedary bag.

So the whole system is pretty well sealed. I can walk away and come back to a full Hydromedary bag. And there's still water in the dirty bag that couldn't come out b/c the Clean bag is full, so I either fill up a 1 liter Aquafina bottle (backup water for whatever), or fill up a pot for some hot coffee.

It's not the lightest system out there. I haven't weighed the whole kit together but the items weighed separately are:
MSR 4-liter Dromedary bag: 6.5 oz.
The dry Swiftwater – 4.35 oz.
Katadyn Bottle Adapter with Activated Carbon: 2.15 oz.
Swiftwater bottle cap: 1.5 oz. with cap removed.
Total 14.5 oz.

It's not SUL by a long shot, but for me, it's a reasonable weight considering that it creates purified (Swiftwater), good-tasting (Katadyn carbon) water. I don't have to worry about chemical treatments being sensitive to time, water temperature, cloudy water. And it's versatile too. I can (and sometimes do) use the Swiftwater as an inline filter from my hydration bag, though it takes allot of sucking.

I did basically what Travis did recently except I used a dry bag instead of a Nalgene canteen. Works, but flow rate is pretty low. I don't care, I just like to make cr*p. Unless I can improve the flow, I don't see this making much trail use versus a pump, but it was a fun DIY thing with my son.

Jbo

Hey Rob,

How fast does your sawyer .02 filter in a gravity setup? I'm curious how it compares to the .1 filters.

Thanks
SFH

http://www.backpackinglight.com/cgi-bin/backpackinglight/reviews/display_reviews.html?forum_thread_id=5536&skip_to_post=251982#251982

Ken's review has way more info than I can provide, but the short answer is that my experience agrees with Ken's and it takes 60-90 seconds per liter on average.

Ken commented that the flow rate went down allot after 10 days of use and that backflushing wasn't required. My longest trip was only 5 days, but I didn't notice a a difference in the flow rate. I should've also included this in my post, but I use a coffee filter at the outlet of my dirty bag. I just leave it scrunched up in the tube. If it collects too much gunk, I just rinse it off and continue to use it.

May I refer you to this posting for what I am about to explain.

http://www.backpackinglight.com/cgi-bin/backpackinglight/reviews/display_reviews.html?forum_thread_id=5536&skip_to_post=251982#251982

After further refinement I find this “system” to perform excellently. I updated the collection bag (green in the pic) to include a sewn in 5 micron pre filter. I purchased the material from globalfiltercorp.com (Type Fiber, Micron Rating – 5, Bag Finish – Plain, Bag Size – 1, Bag Style – PESS) but I think you can buy this on line.

I use this system exclusively when I backpack with my four grand children. The filter works flawlessly and produced water from the .02 micron filter quickly and in large amounts. On a nine day trip this year with the young one I did NOT need to back flush the filter and the filtering rate did not slow substantially…..I did not quantify flow rates so I do not know exact differences if any. (I did bring a large 60 ml syringe for back flushing if needed.) Total weight of the system [SAWYER WATER PURIFIER (.02 micron) (8.75oz WET /FLUSHING SYRINGE (1.12oz)/ BAG, (5 micron) prefilter&HOSE (4.26oz)/BAG (.35oz)] – TOTAL 14.7 oz. While the system does not fall within what you would call a “light” water treatment method, as compared to chemical or UV technology, it does provide water in large amounts that are virus free in little or no time.

"I use a coffee filter at the outlet of my dirty bag. I just leave it scrunched up in the tube."

Rob,
So, you stuff the filter Into the 0.25 ID hose going to the Sawyer? Is it a paper filter or fiber? It seems like it could get to far down the tube to retrieve. Is that an issue? So, how do you retrieve it?

Thanks.

In my original test describe in my post above I used Pelon pre filter (cloth pore space aprox. 5 microns) over the intake 0.25 ID hose that was connected to the plastic fitting within the collection bag.
.

The observations I noted:
• In a test environment that was presented in my testing model there were no issues with flow rate OR plugging.

• In a BP environment (Lake Michigan early spring with high concentrations of Cladophora, a common filamentous green alga) the small area of the filter plugged and needed constant cleaning…..the reason I went to the larger filter area in my model and solved this issue without a reduction in flow rate.

Ken,

Which version of the sawyer purifier comes with quick disconnect fittings? I found one online at Walmart that is only $59(purifier). Did your SP 135 include a syringe as well, im not seeing that in the online item descriptions.

I am replicating your filter setup with a few changes:

I have a larger prefilter(a cut section of the bag) above the setup, so that when it clogs i can just take it off, clean it, and put it back on. I have also added a charcoal element via an inline fuel filter.

If i buy this cheaper version, can i buy quick-disconnect fittings for it(if so where?)?

ADD 4-5 oz for purifier weight to the image above, i made that drawing with the filter in mind not the purifier. But like you, i would rather just have instant clean water than treat with chems.

QUESTION: “Which version of the sawyer purifier comes with quick disconnect fittings?”
>>>>>Sawyer Purifiers do not come with a quick disconnect. I designed my own system that is NOT designed to QUICK DISCONNECT and purchased the .02 micron purifier at Wal-Mart…….lowest price on line.

"Did your SP 135 include a syringe as well, im not seeing that in the online item descriptions."
>>>>>My doctors nurse provided it free when I asked her.

Items used in my bag:
GREEN BAG: Sea To Summit (http://www.seatosummit.com.au/showdetail.php?Code=AUDS): Ultra-Sil™ Dry Sack – 8 Litre 17cm(dia)x 46cm / 6.5" x 18" 1.1oz/30g

WHITE NYLON PARTS:
US Plastics (www.usplastic.com):
Female Adapter Nylon Fitting 3/8" x 3/8" (item #62170)
Male Adapter Nylon Fitting 3/8" x 3/8" (item #62176)
3/8-16 Thread – PVC-1 Hex Nut Washer (item #91175)

PRE FILTER – sewn in the interior at the TOP CLOSURE of GREEN BAG above:
Global Filter Corporation (globalfiltercorp.com) 5 micron pre filter – Type Fiber, Micron Rating 5, Bag Finish Plain, Bag Size 1, Bag Style PESS) …. Biodiesel bag would work great also

NOTE: The weight of the WET SAWYER .02 micron purifier (8.75 oz) upon charging at home can increase to 9.0 oz after extended usage, weighs more than a DRY SAWYER non charged purifier…..something you cannot get around for the purifier to perform!

I just got back form the tractor supply store and i got one of each of these tractor filters:

My plan is to fill them with high quality(high adsorption) activated charcoal. That way i don't have to buy a new carbon filter everytime its clogged/done. The kohler one at the top has a nice metal mesh basket, about as round as a quarter, maybe half an 3/4 of an inch long inside it. It should work nicely, i just cannot figure out a way to get them undone. They seemed joined at the top, i can tell at one time it was two seperate pieces, but its very difficult to undo. If anyone has any advice on seperating the halves, let me know.

AFter puncturing my hand with a screw driver and lots of frustration, i finally got it open. It was molded and was not easy to open. The one that is not pictured below(the other one pictured above) was alot easier to open. Anyway, you can see below that is a very nice little basket. It has a very very fine(i suspect micron) mesh:

But it also has a strange very very strong clear glue that i am wary of, and i am trying to remove all of it.

I plan to reclose it with duc-tape, which sticks to the plastic very well. When i need to refill it, i will just remove the tape and refill.

It would be better if i could find something that would seal itself, was small, and would fit in the hose. I could then just put a mesh basket/small micron bag in it.

Heres the other one, took about 2 minutes where as the first one took an hour:
I hope its non-toxic. =/ Cost: $5

This second one is much better because the filter section can twisted on and off the device. Its not glued with the strongest glue in the world like the other one, although i like the look of the mesh basket better.

Can anyone recommend me a high quality activated carbon with a high adsorption? I read that the quality of the carbon greatly affects its ability to clean.

Ike,

Thank you for placing the rabbit in your rendered tree so as to approximate scale.

I know, whats an image without scale?

Ike,it seems like every aquarium store feels that their charcoal is the best. The only source I'd think would be dependable is the replacement pack for Katadyn's carbon filter. I found some on Amazon, for like $10 for a 2-pack + shipping. I was thinking of getting a couple packs, but they're not cheap. It seems like those Katadyn packs are a bit hard to find. But at least they would show you what Katadyn thinks the grain size should be. I tried some regular aquarium activated charcoal in my Silt Stopper, and it did no good as far as removing the chlorine taste of the pills. I'm thinking that you need a good volume of charcoal to be effective (note the dimensions of the Katadyn Carbon Filter, as shown on REI). I hope your tractor filters hold enough charcoal to be effective. Please let us know how it works for you. Several of us are pulling for you, Ike.

Thanks Gary. Im checking out iodine number, adsorption rates, etc, in relation to activated carbon. Then you also have impregnated VS granulated carbon. I think a powder would work best in this instance, but dunno if it would bleed through the filter or work its way upward into the sawyer. So im leaning toward granular. Trying to find one in bulk that works in small amounts per my filter. Maybe someone more knowledgeable than me in this area. will help us out. I dont want to buy the katadyn ones, as we all know their heavily marked up. I agree with you and would like to find a cheaper substitute for the katadyn, afterall, thats the point of this whole thing.

This is the best site for buying AC. They list all the technical data like iodine numbers, surface area, etc if you click on the small text: "technical data" after clicking on an item.

http://www.buyactivatedcharcoal.com/charcoal_water_filter

This is exactly the kind of thing we need for the carbon filter, but it is too small.

http://www.industrialspec.com/serviceable.html

Ike…To give you some help on your query, "If anyone has any advice on seperating the halves, let me know."

>>>>Try placing the filter in hot water for a minute and then see if it will loose the glue so you can twist off.

It's a Melita Paper cone filter. I don't stuff the entire filter into the tube. The MSR Dromedary that I use as a dirty bag has a cap with a nipple for attaching the tube. I take the filter and crumple/compress half of it up by rolling it between my hands. What's left is kind of like a flower shape. The bottom part of the cone filer is crumpled into a thin role that I can feed into the nipple (this is the "stem" of the flower), and the other end is left more open (the "flower" if you will). The flower part that's left open keeps the paper from going down further into the tube.

I see allot of good suggestions in this thread of more durable alternatives, but honestly I haven't had any problems with using the paper coffee filters.

I always take some coffee filters with me anyway. They weigh almost nothing and they have so many uses. Sometimes I even use them for coffee.

Ok, after a few days of research into activated carbon, i found three great links that explain everything one would need to know when selecting activated carbon for water filtration.

1. Wiki, scroll down to properties section:
http://en.wikipedia.org/wiki/Activated_carbon

2. Particle size chart:
http://www.buyactivatedcharcoal.com/sieve_size_chart

3.Standard Mesh sizing(to keep powdered carbons/small granules from escaping your mesh. Look at the chart in the lower right)
http://www.espi-metals.com/tech/mesh.htm

Example of technical data AC from buyactivatedcharcoal.com:
http://www.buyactivatedcharcoal.com/granular_activated_charcoal_8x16

Bulk AC:
http://www.buyactivatedcharcoal.com/bulk_activated_charcoal

Note the iodine number, apparent density, hardness number, ash content, and the 8×16 size of the carbon-meaning greater than 8 less than 16 on the particle size chart above.

This is all the knowledge you need to buy AC. With that in mind i am deciding between these two right now:

http://www.buyactivatedcharcoal.com/granular_activated_charcoal_8x16
http://www.buyactivatedcharcoal.com/granular_activated_carbon_12x30

I may order smaller sizes of both, and see which is better. However, the ability of activated carbon to do its job depends of course on the quality of the carbon, but also on the time of exposure. Will there be enough carbon in that little fuel filter to have an effect? Will the water be in contact long enough to be cleaned? I will get back with test results next week after all my stuff for this comes in. Because this stuff is really high quality, i will at least be able to rule out the AC as being defective. If it works we will have a replinishable, cheap way to utilize carbon filtration in our gravity setups without having to buy katadyn carbon filters or frontier pros.

When you get all finished with this exercise, how do you intend to accurately measure the filter performance?

–B.G.–

As of right now my plan is to take murky water and run it through the system. The sawyer will do very little for the color/apperance/odor, so if the carbon is working, it should look like bottled water. If anyone has better ideas for testing it, please let me know, i'm all ears. Maybe add some dyes and see if it takes those out?

I wonder if you could just put some activated carbon in some dialysis tubing, seal the ends, and leave it in the water bottle/bladder.