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Post by cweston on Jun 21, 2023 11:34:16 GMT -8
I have a 4-liter Platypus Gravity-works filter system, and I love it.
I'm nowhere near the listed lifespan of the filter, but it has been the case for a while now that it hardly flows at all unless I aggressively backflush. (If I have clean water available, I start with a few ounces in the clean bag, since that makes it much easier to backflush.) Once you get it backflushed, it flows fine.
I've always babied the filter: it hasn't been dropped, I take it to bed with me on cold nights so it doesn't freeze, etc. As I said, I'm nowhere near the stated life span in terms of liters filtered. This seems to be a common complaint with these filters.
My only concern is if this is a sign of a decline in filter performance. I don't want to spent $75 on a replacement filter, but I will if there's a chance this one isn't filtering as thoroughly as it should be.
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ErnieW
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Post by ErnieW on Jun 25, 2023 16:34:24 GMT -8
I will if there's a chance this one isn't filtering as thoroughly as it should be. If the filter started filtering faster that would worry me since the filter element was probably breached. Slower and slower just means more particulate is getting stuck in the pores of the filter in such a way as back washing doesn't get it out but it is still filtering to size specs just less volume/time.
P.S. Looking at the system online you might be able to use a Sawyer Squeeze as a replacement with a hose kit (like $35. Lifetime warranty)
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Post by Coolkat on Jun 26, 2023 4:15:52 GMT -8
Looking at the system online you might be able to use a Sawyer Squeeze as a replacement I've seen Sawyer's Squeeze do the same thing in the backcountry (two different hikes, different people) and no amount of back flushing helped. However, I will say that recently my beloved Katadyn BeFree has also (twice) exhibited the same behavior. Just recently I emailed Katadyn and explained the situation. They are sending me a free replacement but in all reality I've lost confidence it and I'm not sure I will be taking it on any more hikes. On my recent hike my other backup also failed and I ended up boiling my water. That was a first for me. |
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Post by cweston on Jun 26, 2023 4:38:24 GMT -8
They are sending me a free replacement but in all reality I've lost confidence it and I'm not sure I will be taking it on any more hikes. On my recent hike my other backup also failed and I ended up boiling my water. That was a first for me. Just to be clear, mine hasn't failed--it works perfectly once you aggressively backflush it, which is fairly easy to do with a gravity rig. It just means a few extra minutes and hassle, and a little bit of anxiety that maybe it will stop working altogether at some point. (I am the kind of BPer who has a little low-level general anxiety about gear failure in the field anyway.) |
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ErnieW
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Post by ErnieW on Jun 26, 2023 5:08:57 GMT -8
Moving water can suspend fine particles that can quickly clog a filter. Back washing should clear this but if you turn around and filter the same water it will just clog right away again. I find this particularly bad with streams that have clay banks.
I used to carry a two gallon water bag. I would fill it and let it sit for a while then filter from the top down with my MSR Waterworks to avoid the sediment in the bottom. Now that I carry a Sawyer and a CNOC bag I fill the CNOC and hang it cap down. If I suspect sediment I loosen the cap and let a little gush of water out that I hope flushes the settled sediment.
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Post by Coolkat on Jun 26, 2023 6:27:08 GMT -8
Just to be clear, mine hasn't failed--it works perfectly once you aggressively backflush it, which is fairly easy to do with a gravity rig. Yeah, I realize that yours is working after backflushing. I was really responding to Ernie's suggestion of going to the Sawyer system. I guess technically I can't say that my BeFree failed since it would filter with just barely a trickle of water while constantly pushing on with a tremendous amount of force, while it use to flow just by holding it upside down. It supposedly will clean if I shake it vigorously or swish it. This helps sort-of for about 30 seconds. I probably could have used it but it would have taken 30 minutes to filter 1 liter. I just gave up and boiled my water. |
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ErnieW
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Post by ErnieW on Jun 26, 2023 6:39:37 GMT -8
I got into a similar situation in Joyce Kilmer in the summer. Just my MSR Waterworks and it kept clogging. We did boil water but ran out of fuel. It was hot. The water was not safe to drink but dehydration was getting dangerously bad in the summer heat. We just toughed it out. We had left a couple of bottles of Gatorade in the cooler in the car. One of the best drinks I ever had when we got back to the car.
After that for several years I carried Aqua Mira as back up. I didn't need it again and gave up carrying it.
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Post by cweston on Jun 26, 2023 6:49:51 GMT -8
After that for several years I carried Aqua Mira as back up. I didn't need it again and gave up carrying it. Yep. I typically carry Aqua Mira as back up as well. They do expire and I eventually have to buy more that I likely won't use either. For weekend trips it may be overkill, but if you're going to be days away from the car, I think it makes sense. |
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Post by nickhowes on Jun 26, 2023 11:58:57 GMT -8
I have a 4-liter Platypus Gravity-works filter system, and I love it. Yeah, me too. Mine is six years old and behaves just as you describe: once you backflush it, it works great, but it's a bit of pain sometimes to "get it going". My guess (and it's only a guess) is that as the filter "clogs", it traps air which prevents the water from flowing. Backflushing it helps clear the air. I've never had any problems getting it to work, but it's not always instant. I wouldn't want to go back to the old mechanically driven filters. |
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Post by BigLoad on Jun 26, 2023 20:09:03 GMT -8
It seems to me that gravity filters have a fair amount of sensitivity to priming. I think it's less of an all-or-nothing proposition than with most pumps, but I get the best results by filling the element with clean water after a backflush and before filtering.
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Post by Joe Hiker on Jul 4, 2023 8:50:06 GMT -8
I've had the same rig and the same issue. I ended up taking advantage of a member coupon and getting a new filter. My thinking (as others have noted) is that the sediment simply clogs the filter pores. Backflushing at home with clean water does help "free" it up so it works more as it should, but despite the life expectancy of the filter unit, it's just a matter of time before it clogs again.
With the new filter (used rarely in 2022 and not at all yet this year) I try to be sure and take water from a flowing section of the stream, or at least a section of the source that shows to be clearer than others. I don't really want to prefilter with a bandanna but I have done that once or twice (very sandy, gritty, or green water), and it works.
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rebeccad
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Post by rebeccad on Jul 4, 2023 11:38:56 GMT -8
With the new filter (used rarely in 2022 and not at all yet this year) I try to be sure and take water from a flowing section of the stream, or at least a section of the source that shows to be clearer than others. I don't really want to prefilter with a bandanna but I have done that once or twice (very sandy, gritty, or green water), and it works.
Wouldn’t the least silty water be still water? Fast-moving water doesn’t allow the sediment to settle out. |
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Post by Joe Hiker on Jul 10, 2023 14:43:13 GMT -8
I've seen (and filtered from) both still and flowing sources. In my experience, the stiller the source, the more silt and stuff is stirred up when you draw from it; think of the mud and gunk that swirls over your feet when you step into a still pond. When you draw from a flowing source, you are only taking from the top of the water, and as you note correctly, the sediment is already below the surface.
So while it may seem that the least silty water is still water, consider how you draw water, esp using a gravity bag. You'll likely get about a half-bag of decent (low silt) water on the first pull; then you either wait for the muck to settle or draw up more with the second pull. With flowing water, skimming it off the surface (as the water flows around/into/underneath the gravity bag) is more likely to trap less silt and muck, because it's already below the surface of the water.
Make sense?
The same has been true for using the older style hand-pump filters; the small inlet trap (which also has a weight near it) is going to settle lower and faster - into the silt at the bottom, exactly where you don't want to draw from.
As a wise one has said, though, "my opinions only; your mileage may vary."
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