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Question about DIY Katadyn Gravity Filter
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Feb 21, 2010 at 11:41 am #1255547
I recently stumbled across this post:
I thought I'd test out the concept by using an intact Nalgene bottle (i.e. not cutting the threads off or cutting a hole in the lid) instead of the stuff sac. The filter does fit in the Nalgene opening quite snugly as stated in the post but I'm getting zero flow through the filter when I flip the Nalgene upside-down and hold it above my clean reservoir. As far as I can tell this should work according to those plans. Any ideas why I'm getting no flow? Is it do to the fact that there isn't enough water pressure? It's almost as if there is some kind of vacuum happening. Apologies if the answer is obvious…I'm new to this stuff. Any thoughts are appreciated.
Feb 21, 2010 at 11:54 am #1576709I would think you had a vacuum problem. Air has to be able to get into the Nalgene for water to come out.
Feb 21, 2010 at 11:56 am #1576711I agree with Joe. With the hard Nalgene, its probably vacuum issues. I'm gonna go ahead and pimp my Nalgene/Katadyn MYOG filter. Check these threads.
Feb 21, 2010 at 12:11 pm #1576713Thanks for the replies. I thought it might be a vacuum thing but was confused because it seems that you would have a similar situation with an air-tight drybag. I like your setup as well Travis, although I would personally want more capacity for my 'dirty' bag. Guess I'll have to try the real deal.
Feb 21, 2010 at 12:16 pm #1576716FWIW, the collapsible Nalgene I'm using is 32 ounces. It can also work with the larger size, providing the opening in the nalgene is the same, which I think it is.
Feb 22, 2010 at 4:52 pm #1577227This just gave me an idea… ;)
Feb 22, 2010 at 4:57 pm #1577231Uh oh. Javan's thinking again…. ; )
Feb 22, 2010 at 6:33 pm #1577258The filter referred to in this thread as well as all the ones I found in the links in this thread have a design deficiency. They put the filter at the source so the water pressure is much lower than it would be with the filter at the other end of the hose. It might not be too bad with a fresh filter, but I think it could become problematic as the filter starts to clog over time.
Feb 22, 2010 at 6:39 pm #1577263Very possibly true. I'm interested to see how this filter works over time, but so far, there's been close to 100 liters of water through this filter cartridge. I still get about 2 minutes per liter.
Feb 22, 2010 at 6:51 pm #1577272I'm sure a lot depends on the porosity of the filter and what's in the water. I use a Sawyer 0.1 micron filter and it definitely benefits from the high head pressure.
Feb 22, 2010 at 6:55 pm #1577273The Katadyn has a 0.3 micron rating, so it is a bit more porous than the Sawyer. I would imagine things would slow down a bit if the water was quite goopy. Ew.
Feb 22, 2010 at 7:04 pm #1577279I've tried it nearly both ways, and have always had a much faster flow with more 'space' between the water and the filter. It's worked both ways, just better with the filter lower in the hose.
As far as the filter not working at all in the Nalgene setup for Nathan, was it a brand new filter? If so, you probably just had to prime it. After that it'll probably work fine.
Feb 22, 2010 at 8:44 pm #1577318With the Cantene (soft Nalgene) I start it with a squeeze and then it keeps going. I cannot get any flow out of the Lexan version. (that is with the filter inside the Nalgene) Sucking works but does not create a flow when you stop.
FrancoFeb 24, 2010 at 3:12 pm #1578149I had a problem similar to yours and my solution may help you…I made up the whole filter thingey, hacked everything together, filled it with water, and just a couple drips came out. You have to have a hose on the nipple of the filter (and sometimes give it a little suck to get it started).
Feb 24, 2010 at 3:17 pm #1578153Rob,
Yes, the hose made it work for me also. I didn't get much flow without it. Something to do with physics I think. -
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