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anyone using a gravity filter
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william hutchinson
(okuncool) - F

Locale: midwest (boo hoo)
anyone using a gravity filter on 10/09/2006 13:29:35 MDT Print View

wondering if anyone out there is using a gravity filter system, and if so what are you using. i was thinking about using the seychelle filter with a couple of platypus bags. anyone out there using somthing different i would love to get input from others about their system. thanks


Locale: South West US
Re: anyone using a gravity filter on 10/09/2006 14:28:38 MDT Print View

Hey Will,

Yes I use a homemade version based on Ray Jardine's design and think the world of it. Really easy to fill and fast to filter (about 1L/min) and resonably lightweight (6.2oz when dry). Very easy to make.

Some people have posted positive things about the H2O Amigo and Seychelle filter, but I am not a fan of either one.

Another good option is Aqua Mira though, I gave it up after using it for a week straight due to wait times and taste.

Benjamin Tomsky
(btomsky) - F

Locale: San Francisco Bay Area
Seychelle gravity filter on 10/09/2006 15:41:00 MDT Print View

I used a Seychelle inline filter as part of my hydration system for a few hundred trail miles (over perhaps five trips totaling three weeks). I used it inline straight from a dromedary and in a gravity setup. At first, it was OK, but grew slower and slower to the point that it is essentially worthless now. At it's best, it would filter 4 liters of water in a few hours (I always used it overnight, so can't say for sure). However, that performance didn't last for long, despite vigorous cleaning and careful source selection.

I have since switched to Clearwater and Aqua Mira. Used at lower concentrations, I don't mind the taste too much, and the dependability is unbeatable...

Michael Davis
(mad777) - F

Locale: South Florida
H2O Amigo on 10/12/2006 10:19:32 MDT Print View

I use the H2O Amigo from ULA. Love it! Works great, it's fast, no maintenance, has a pre-filter. Weights 9.6 oz for complete kit.

nick lidakis
(nyc_paramedic) - F
Re: anyone using a gravity filter on 10/22/2006 06:56:07 MDT Print View

I'm using the ULA h20 Amigo, albeit modified depending on my needs. I replaced the stock drawcord water bag with an ultralight 4 liter waterproof drysack. This way, I can hang the bag in camp and have extra water, and also wash my hands without fear of spilling any water. The stock drawcord bag, which doesn't seal close at the the top, would sometimes shift postion and leak or spill water out.

I also can use a General Ecology First Need replacement canister instead of the stock inline filter. The GE canister, as per the manufacture's specs, can be used in gravity filter mode sans pump. This canister is the only mechanical "purifier", not filter, that is EPA rated to remove viruses, protozoa, and bacteria without the use of iodine or other chemicals.

The canister is slighty heavier than the ULA supplied one, but I feel a little bit safer that no matter what water I might encounter, it will be 100% potable.

mark henley
(flash582) - F
Re: Re: anyone using a gravity filter on 10/23/2006 15:13:32 MDT Print View

I've used the Amigo and loved it, switched to chems for the lightness and like them, but now I purchased a 2 oz inline filter from I put the filter inline in my platy hydration tube.


Not only does it do great job as an inline filter, but slide off the removable platy bite valve and you convert it instantly to a gravity filter with a better flow rate than the amigo.

I normally just carry the platy during the day and a Liter of gatorade, then filter another 2+L plus refilling the platy for dinner and breakfast.

Fill up the Platy in the morning and you're off down the trail in just a minute.

0.7 oz for the 1L platy, 2 oz for the filter, 4 oz for the hydration setup, and 1.4 oz for the 2+ L platy ... 8.1 oz for the whole setup vs 7 oz for just the Amigo and no extra baggage in your pack

Bill Fornshell
(bfornshell) - MLife

Locale: Southern Texas
Gravity Filter on 10/23/2006 15:32:10 MDT Print View

My home-made Gravity Water Filter only weighs 5.61 ounces. Add the Platy 1 liter at (your weight) of 0.7 ounces and my set-up only weighs a total of 6.31.

I first started out with a stock Amigo filter but dumped the filter that came with it for the much better Katadyn Hiker Pro Microfilter. Next came a new bag made from Cuben Fiber and a lightened filter, etc, etc and soon it was a completely new set-up. There is a thread in the MYOG Forum showing how I did it.

Stephen Eggleston
(happycamper) - F

Locale: South Bayish
RE: gravity filter on 10/24/2006 17:56:30 MDT Print View

I used the seychelle in a gravity filter set-up for some time. I used a big zip platy on top with a platy resevoir underneath. I set it up so that while hiking the filter outlet was attached to hose/bit valve. Then when at camp I pulled the hose/bite valve off the outlet and attached a short hose and resevoir.

I prefer the Aqua Mira currently. Gravity filters have the advantage of reducing your chemical exposure, just be sure to understand the filter's capabilities or lack there of. The seychelle filter usually left me with runny/loose stools due to inadequate filtration ~:(

william hutchinson
(okuncool) - F

Locale: midwest (boo hoo)
Re: RE: gravity filter on 10/28/2006 18:26:11 MDT Print View

"The seychelle filter usually left me with runny/loose stools due to inadequate filtration ~:("

has anyone else experienced this problem. my issue is i am prepairing for a thru-hike of the pct and i am worried about chemical exposure for such a long time. i really am not sure what my solution could be. i had planned on using two bladders and a seychelle in between but "runny/loose stool" is not going to cut it for me. i would rather use chemicals. there is a new in line filter i saw recently called the sawyer in line filter available at rei. has anyone experienced that or heard anything. i have always hated regular filters because they weigh so much and take forever to pump. i thought the gravity filter would be a good solution, becuase it would reduce weight and i could do other things wile it was filtering, but it sounds like it might not be the safest solution. any thoughts.

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: RE: gravity filter on 10/29/2006 01:02:01 MDT Print View

Seychelle is, in reality, a cyst filter. I can think of a few reasons why one may have problems using it.

1. The filter is cracked and so is ineffective.

2. Bacterial diarrhea (bacteria are generally too small to be filtered by the Seychelle based upon the Mfr's statement of its absolute pore size; bacteria, from more than one taxonomic family, can cause issues in the human's hintermost parts)

3. Sometimes Crypto can fold over on itself (while not the most common shape for Crypto, i've seen this myself under a microscope) and in this shape may(???) be able to pass through the Seychelle pores.

IMHO, Giardia should NOT be able to make it through an undamaged, properly functioning Seychelle.

You might consider trying the SteriPen UV-C water purifier coupled with a pre-filter (as simple as a bandana over the mouth of your 1L container). Mine takes 4xAA batts (not sure about what batts the newest smaller model takes). I know, I know - batteries; not the ideal solution. You might query the Forum users who have hiked the PCT about the availability of AA batts vs. CR123 batts (used by the AquaStar UV-C purifier) for resupply.

Edited by pj on 10/29/2006 01:34:24 MDT.

Mike Storesund
(mikes) - F
Re: anyone using a gravity filter on 10/29/2006 08:34:06 MST Print View

I use a gravity filter most of the time, with Aqua Mira or Klear Water as backup or extra precaution if I really want to make sure I get the best drinking water I can.

I started using a platypus combination where I have the 4 liter water tank (big zip and handles on top, tube hole on bottom), the filter link attachment to a 3” piece of hose then to a 5 micron Sweetwater filter (used as pre-filter) to a 3’ piece of hose to the 2 micron Seychelle filter and a final short piece of hose. Everything rolled up in the water tank and weighs just over 10 ounces. Since then I purchased the H2O Amigo and use that as my primary gravity filter.

Being only 5’6” I do need to tie it off on a higher branch, but I’m okay with that. If I feel the need for extra precaution, I can always add the chemical treatment after the water has been filtered.

Edited by mikes on 10/29/2006 08:38:01 MST.

william hutchinson
(okuncool) - F

Locale: midwest (boo hoo)
nick on 10/31/2006 17:02:50 MST Print View

nick- you said you were using te general ecology canister in a gravity setup. how well is that working for you. what is the flow rate. how heavy is the canister. i cannot find any information on the net about flow rate or weight of the canister alone.

(T-BACK) - F
water filters on 11/01/2006 09:13:26 MST Print View

I was inspired by Bill F's filter mods and so purchased a Hiker Pro filter and started cutting. Instead of a bag I used platapus 2L bag with a shower kit attached. I mated the outflow nipple from the filter to the shower intake hose. Remembering what a friend told me he had done, I used my silnylon bucket and put a hose outlet on it. On the oppisite end of the hose I placed a cheep, generic, plastic fuel filter. I gather water in my bucket. I don't have to be very careful anymore about floaties and silt because I filter those out before the water ever touches my bio filter. I've used it for three weeks and have no visible soil on the Hiker Pro. When the pre filter gets slow I just flip it around on the tubing and backflush it and I'm good to go. Eventually it will clog but then I'm only out $2.50 for a new one verses the cost of the Hiker. So far it has worked well for me. I could try and post some pics if you are interested.


william hutchinson
(okuncool) - F

Locale: midwest (boo hoo)
Re: water filters on 11/01/2006 12:31:51 MST Print View

yeah i would definately be interested in photos
i am still trying to figure out what setup i want. i am starting to consider one of those uv lights.

(T-BACK) - F
Water Filter on 11/01/2006 17:26:27 MST Print View

Here are a couple of pics from my last AT hike. Hope they help.

Prefilter on top, Biofilter in platy.Setup on hillside

nick lidakis
(nyc_paramedic) - F
Re: nick on 11/07/2006 15:26:45 MST Print View

The canister (just weighed it again) is 11.7 ounces saturated. I can fill up a liter bladder in about two to three minutes. With the tubing and the ultralight drysack, the total comes in to about 13.5 ounces.

The General Ecology website:
Particle Retention (microns)
.1 nominal
.4 absolute

It's not the most ultra-light. It is the lighest, most reliable, and absolute safest "purifier" setup I can think of right now. There are lighter "filters", but they won't protect you against bacteria and viruses.

I've researched chemical tablets, and they depend too much on water temperature and wait times.

The Katadyn Micropur MP1 Purification Tablets specify a fifteen minute wait to kill bacteria and viruses, and up to a four hour contact time to kill Cyryptosporidum. But, that is at a water temp of 4 degree Celcius, or 39.2 degrees Fahrenheit. I can't find any fact sheet or manual (every other product/filter has a PDF) on their website concerning these tablets. What if the water you encounter is much colder?

I guess one can use the stock seychelle to remove cysts, and then the Katadyn tablets to remove bateria and viruses.

I almost forgot to add that --concerning the custom setup I have-- one can increase the flow rate by rolling and squeezing the closed drysack water bag, like a tube of toothpaste, if you will.I thought of this one day when I realized that I always squeeze liter bags of I.V. saline to incerase the flow rate to patients who are in severe stages of decompensated shock.

Edited by nyc_paramedic on 11/07/2006 16:08:11 MST.

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: nick on 11/08/2006 00:55:13 MST Print View

Just an FYI.

There are many sub-micron filters available that will eliminate bacteria.

And, much to my surprise and initial extreme skepticism, one filter (from Sawyer) claims to eliminate non-filtrable (as they were always previously known) viruses, measuring tens of nanometers in size. As Gomer Pyle, USMC, used to say, "Surprise! Surprise! Surprise!".

d k
(dkramalc) - MLife
Re: Re: Re: nick on 11/08/2006 09:36:46 MST Print View


Have you used the Sawyer? I've been intrigued by the description, but wondering how much suction/pressure is required to get water to flow through such a fine filtration. I'd emailed them, but never got a reply (though it may have been filtered out by the spam filter at work, where I emailed from).


paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: Re: Re: nick on 11/08/2006 10:02:47 MST Print View


No, i haven't used the Sawyer yet. It's on my "soon-to-be-acquired" list though.

As far as suction, they say that is NOT an issue due to the surface area involved. I guess i'll find out for myself next late winter or early spring when i acquire one.

Sorry i couldn't be more help.

d k
(dkramalc) - MLife
Re: Re: Re: Re: Re: nick on 11/08/2006 10:17:13 MST Print View

Thanks, pj (also for your answer on the Epic on another thread).

I think the Sawyer filter is probably in my future somewhere. I like Brian's setup for gravity filtration also (substituting the Sawyer?), though I'm not sure what type of hose fitting he got on the silnylon bag, or how it's attached. It looks from the picture to be smaller than a garden hose fitting.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: nick on 11/08/2006 15:26:34 MST Print View

> one filter (from Sawyer) claims to eliminate non-filtrable (as they were always previously known) viruses

The lab report says a pressure of 40 psi was used to push water through the filter. That's equivalent to 30 metres or 100 feet of water head. This is a LOT of pressure - a LOT! And I bet the flow at the far end was not fast.

Look guys, there's an old rule in the marketplace. "If it seems too good to be true ..."
So be careful.

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: Re: Re: nick on 11/08/2006 15:44:56 MST Print View

Dr. C, many thanks for the "heads up" on the pressure issue. you said, "a LOT!" - you ain't kiddin'; "a LOT!" is perhaps a bit of an understatement!!!

aaron eshelman
(djaaronreed) - MLife

Locale: Central Rockies
40 PSI for conditioning. on 11/12/2006 14:57:08 MST Print View

The 40 psi was for the initial conditioning. The actual test was performed at 20 psi.

"The test waters were passed through the water filter in a manner similar to
how they would be used by the consumer (20 psi)."

Anyone know if this is a "normal" psi for drinking through a tube?

I too am curious about these filters. They are a little pricey though.

william hutchinson
(okuncool) - F

Locale: midwest (boo hoo)
Re: Re: nick on 11/13/2006 18:59:17 MST Print View

hey nick, i was just wondering about that flow rate on the general ecology filter setup you are using. i am just wondering about how long it takes to filter one liter. i know i am going to use it to filter larger quantities of water somtimes, so if it is going to take 20 minutes a liter that wont work. anyway
thanks for your info.

Aaron Lastname
(Cloudveil9) - F
Sorry to Revive This Thread... on 03/03/2009 09:30:00 MST Print View

But I have a question I'm hoping someone -Might- be able to answer. Earlier in this thread Nick (Who doesn't look like he's been on in a while and I can't PM him) stated he was able to get a 2-3 minute per liter flow rate out of a gravity fed First Need cartridge. I currently use a First Need purifier as it's the only thing I have found that:

1) Removes bacteria, viruses, and protozoa

2) Reduces heavy metals and chemicals in water

3) Improves taste, removes tannin etc. (IE pumps blue water clear!)

4) Does not use chemicals. (More concerned about long term exposure than taste here, but taste too...I filter my water at home for example to remove chlorine etc, don't want to introduce it to my backcountry water if possible)

5) Is fast. While tiring, I can fill up all water containers for 2 people very quickly and it's instantly ready to drink...No waiting 30 minutes - 4 hours.

Of course the drawback is weight of course but I have found no other option. I was thinking about trying Nick's method of just using a water bag and the canister to save about 8oz but I tried last night and got a 1 liter / 13.5 minute flow rate! This was with a canister that is almost new. I removed the pump assembly, then setup the waterbag system that is included with the First Need system and used the included hose (3 feet?) and hung the full bag as high as it would go with that hose above a Nalgene bottle. 13.5 minutes later I had a full bottle.

Does anyone have any ideas how he achieved the flow rate he stated? Or are you out there Nick? I also compressed the water bag to get it going etc but still 13.5 minutes. Do I need a longer hose, etc? Thanks for any tips!

Michael Davis
(mad777) - F

Locale: South Florida
Re: Sorry to Revive This Thread... on 03/03/2009 10:31:28 MST Print View

Aaron, I use a Sawyer viral filter, which has very similar specs compared to First Needs, in a gravity configuration. I haven't timed it but I know it doesn't take anywhere near 13.5 minutes per liter.

However, the trick with this one at least, is to prime the filter before your trip by backflushing is with the faucet attachment and leave the water in it!

This system doesn't save weight; the gravity bag + hose + dry filter weighs 9.6oz but with the wet filter, it all adds up to 14.9 oz.

However, it does save work and it filters everything, including viruses from swamp water, without any waiting or chemical side effects.

I use a Steripen Adventurer in clear mountain streams and with either system, I carry chlorine dioxide tablets as back-up.

Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
Re: Sorry to Revive This Thread... on 03/03/2009 10:44:59 MST Print View

The Sawyer viral filter won't get rid of chemicals by itself so if that's an issue, you need to add a charcoal filter.

BUT, if you include a charcoal filter, you can also add a little chlorine (2 drops/liter) to the water to kill viruses. The charcoal will remove the chlorine after it does its job and many other chemicals as well. Then you can use the considerably cheaper Sawyer 0.1 micron filter which removes everything except viruses.

I never timed it, but if I had to guess, the flow must be a half liter per minute.

There's a photo of this combination in this thread:

Aaron Lastname
(Cloudveil9) - F
Thanks on 03/03/2009 10:48:32 MST Print View

Thanks Michael, I have been looking at that filter, but was scared away by the REI listed weight of 20oz, no better than my First Need. However it appears that 20oz must be incorrect or the system can be broken down into something lighter. Your system would still save me a lot of weight - My First Need with cartridge and pump weighs 22oz with a used canister. I find the listed weight of 16oz incorrect, and it seems that after you use the cartridge one time, it gains 4oz. (I have a cartridge I've used that was flushed out after use and has been sitting in my closet for 6 months, and it is still 4oz heavier than a new one) I guess with that Sawyer I would be losing that ability to turn blue water clear and remove bad taste while reducing any heavy metals and chemicals, but gaining in that I would never have to replace a cartridge. Hmmmm.

Aaron Lastname
(Cloudveil9) - F
Nice Setup on 03/03/2009 10:53:38 MST Print View

Herman, I like that setup. Kinda going against my "Mantra" to add chlorine and then take try to take it out, but hey that's the same thing I do at home (Or try to) with my Brita. Maybe I'll have to make some compromises to achieve my goal!

Aaron Lastname
(Cloudveil9) - F
Triple Post on 03/03/2009 11:07:19 MST Print View

Now that I think about it maybe Michael's viral filter with the Katadyn charcoal filter is the way to go. Don't know about flow rate, though. No chems added, however.

Justin Marney
(gotascii) - M

Locale: Shenandoah
anyone using a gravity filter on 03/03/2009 15:17:46 MST Print View

@Michael & @Herman Is this the Sawyer you guys are using? Is it possible to prime the filter on the trail or does it take more pressure than one could muster via lung power?

Edited by gotascii on 03/03/2009 15:30:05 MST.

mike leary
(backingit) - F
Big Berkey Gravity Filter? on 04/17/2009 19:16:32 MDT Print View

How about a Berke Filter. A smaller one like the big berkey or berkey light would be good as a base camp solution. albeit a little bulky to manage.

Walter Carrington
(Snowleopard) - M

Locale: Mass.
What diameter tube for filters? on 05/31/2009 15:15:18 MDT Print View

A possible easy way to set up a water filter is to use the top for a nalgene water bottle with nipple:
If you pull the moveable part of this nipple you have a nipple about 10mm in diameter. If this fits the tubing required for the filter, then use this wide mouth 96 oz polyethelene water bottle:
The question is the diameter the same as the filters. I'm thinking of using a 0.1 sawyer filter

Samson lee
(Samson) - F
Re:water filter on 10/28/2010 11:08:36 MDT Print View

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Locale: Western Michigan
Informational Help on Sawyer Filters on 10/28/2010 11:21:00 MDT Print View

Gary Ward
(coastalbliss) - F
Gravity filter works on 11/12/2010 15:45:51 MST Print View

I'm surprised there is not more current postings on this topic. It seems there have been some improvements in the last few years on the gravity feed filtration systems. I have an MSR that works great.

I've used the pump-MSR as well. I have one that has lasted about 15 years and still works great with its ceramic filter. It is the old standby. I tried the UV bio-killer pens, but kept having issues with them. I was not impressed. These need some further development to make them bombproof.

I had absolutely no issues this past summer with the MSR gravity feed system. My partner used the Katadyne gravity feed system with the filter in the bag and has some trouble with it being very slow. It was not as easy to flush as the MSR system and she was almost ready to give up until I told her about the MSR system. But to be fair, she was using the Katadyne system in an area with a fair amount of glacial silt washing through, whereas I wasn't.