So I've had a Platypus Gravityworks filter for over 5 years and I gotta say I still love the thing. I've always been very religious about backflushing it before filtering as it says in the instructions, and also cleaning it with bleach at the end of every trip.

Then recently, I loaned it to my daughter for a 4 day canoe trip. I foolishly assumed she knew how to use it. She apparently had forgotten about running a small amount of water into the clean bag, then raising the clean bag above the dirty bag until the air is purged. She just hung the dirty bag and let it filter. She said it was getting slow by the end of her trip, and indeed when I was bleaching it I noticed that even with tapwater in it, properly backflushed per the instructions, it ran noticeably slower than it had before.

Just trying to wrap my head around what happens when you don't do this little backflush. I always assumed that it was about getting the air out of the filter so if you skip the step, why does it seem like the filter is more plugged than before? I guess I don't quite understand what is going on here.

I've already decided that I should just buy another cartridge for 40 bucks and get over it. I can keep the old one around for emergency use.

Not sure what’s going on honestly but I wanted to share I “upgraded” my worthless Katydn 6L base camp filter with an inline gravity Platypus filter a few years ago based on the great examples on this forum. It worked well but I still had to back flush it every 8-10 liters. It was an easy back-flush so I used it for a couple seasons. This year on a couple solo trips I used a Sawyer Squeeze filter in a gravity set up with the Platypus 4L bags and it works really well. I have put over 50L through it over multiple trips and multiple lakes and not needed a single back flush yet. I used it on a family trip as well and it handled those increased demand volumes just fine. I think I am done with the Platypus filters.

The last 5-6 yrs of Wabakimi Project trips we used this filter system daily for about 12 weeks each season. With so much use by so many different people I was always surprised how well it held up and functioned. When I used it I always back flushed it as you described and it always worked satisfactorily. I learned it was also important to make sure any air bubbles in the filter Iine had been bled out. I checked my Platypus instructions and the filter is good for up to 1500 liters depending on water quality. Perhaps you have reached this point?

I thought you back flushed after filtering but maybe doesn't matter. Like you, I always back flush a half of litre or so after each bag filtered.

Good and interesting stuff here, including how-to test the filter. Platypus

get a syringe, fill it with clean water, and use it to backflush your filter. We only need to do this about once every trip, and thereafter the 'normal' backflushing works easier, and the filtering runs much faster.

I don't think it's anywhere close to 1500 liters. I just used it at the start of August and it seemed as fast as when I bought it. It was after my daughter had it out without doing the initial backflush that I really noticed it. I don't really pay that much attention to the speed, except when I'm waiting for enough water to come through for the initial backflush. I also tried blowing backwards on the filter per the instructions, and it passed that test.

Like I said, I'm ordering a replacement--I should have a spare anyway. Just curious as to the function of that initial backflush. Maybe I'll email Platypus.

marsonite: The lakes your daughter was on could also have been a factor:

My initial run with tap water after purchasing my Platypus 4L system this spring was under 3 minutes.

After 3 days on Horseshoe (water that seemed quite clear), and backflushing only occasionally in the field (maybe after every 3-4 cycles I'd do the recommended lifting of the clean bag over the dirty bag) it slowed to 8 min 30 sec. Back home, I backwashed it with my Sawyer faucet attachment and got it down to 5 min 30 sec. I ran a mild bleach solution through and the time improved to 4 minutes.

On our second trip with the filter, 3 days on Gabbro (a lake known to be notoriously hard on filters), and field backflushing again, this time a bit more often, it slowed to around 10 min, sometimes greater. I didn't record findings as well this time during backwash procedures at home, but my final run during bleaching before storage was still around 6 minutes.

So, a significant degradation (half speed) was noted, especially after use in a stained lake known for its high volume of suspended pollen, but I'm still happy with the system. Six minutes is not that long to wait, especially when doing other things around camp. It is, however, enough to make me think about buying a second filter as a backup.

Thanks for the data Schweady. I just went and ran a bag full of tap water through it, and it seemed much faster--I could see the level in the dirty bag go down which I couldn't before. I timed it and it took almost 8 minutes. Based on eyeballing it, I think that is ballpark what it was doing before my daughter took it.

My guess is that some of the microtubes are plugged. I don't think there's a lot of hope in unplugging those tubes really when you think about it. If I run water backwards, it's just going to bypass those plugged tubes and go through the open ones.

She didn't go to the cleanest lakes....Nina Moose, Agnes, and Lacroix. But no different really than the lakes we've used it on.

Yup. Agnes is one of the lakes that has played havoc with my filter somewhat more than others. Along with a lot of other favorite western side river system lakes containing a good supply of cedar pollen...

Yeah they require a back flush to get air out out line to start filtering and you should back flush again after each full filter. I back flush a cup or so back into the dirty bag at the end of filtering. You can really see the dirty water flush back into dirty bag. I've had no filter slow down after almost 14 weeks of use.

I learned with pumping - Katadyn Hiker Pro - that using a collapsible bucket and letting water settle a bit before pumping made a huge difference. I do same with gravity system and it sure seems to help.

Because my local muni water is horrible, I started running distilled water through mine after a trip. It seemed to make a difference for me.

One partial bag of distilled water with bleach run forward and backward several times. One bag without bleach run forward and backward several times. Air dry and put away.

I have gone through 3 plat filters. Ive noticed they keep tweaking their instruction manual. I swear when I bought years back there was a food coloring test.There is no doubt prefiltering is the simple solution. With tap water at home backfill all 4 liters until your happy with the time. I think last time I backflushed 6 times. I suspect the tannin is slowing it more than anything.

I'm kicking around getting one of These to pre-filter for my Platapus..

Especially if I start doing any camping in the St Louis River canoe route..

firemedic5586: "I'm kicking around getting one of these to pre-filter for my Platapus.."

I made one from a sawyer adapter. The inside:







I cut the wire mesh to fit inside the the bottom of the blue cap. It gets trapped in place by the grey cap when they are threaded together. I think it's currently a 25 micron filter mesh.

The o-ring goes over the end of the grey cap and gets trapped between the blue and grey caps. You need to find an o-ring large enough to go around the cap, but with a small enough cross section to get caught under the end of the blue cap.

Looks like this assembled:







Anything that doesn't make it through the filter ends up back in the dirty water bag when I back flush.

Seems funny to me to backflush into dirty bag. Why run the same “dirt” back through your filter when you start filtering again? I remove my filter to backflush so contaminants are discarded. I used platipus and MSR filters for a few years then switched to Sawyer filter. The syringe they supply is worth it’s weight in gold in my opinion. Does a better job flushing with less of filtered water used in the process. But the MSR dirty water bag to me is awesome. The prefilter really helps in my opinion.
The gravity filter system to me is the best thing ever invented... ha!

Hey Ben,

After I backflush I usually dump the remnants of my dirty bag on the shore or back in the lake before refilling the bag. A prefilter is an interesting idea. I've seen it mentioned that a fuel line filter could work too.

houseofspam:
I made one from a sawyer adapter. The inside:




I cut the wire mesh to fit inside the the bottom of the blue cap. It gets trapped in place by the grey cap when they are threaded together. I think it's currently a 25 micron filter mesh.

The o-ring goes over the end of the grey cap and gets trapped between the blue and grey caps. You need to find an o-ring large enough to go around the cap, but with a small enough cross section to get caught under the end of the blue cap.

Looks like this assembled:



Anything that doesn't make it through the filter ends up back in the dirty water bag when I back flush. "

Thanks for the tip!

nctry: "Seems funny to me to backflush into dirty bag. Why run the same “dirt” back through your filter when you start filtering again? I remove my filter to backflush so contaminants are discarded. I used platipus and MSR filters for a few years then switched to Sawyer filter. The syringe they supply is worth it’s weight in gold in my opinion. Does a better job flushing with less of filtered water used in the process. But the MSR dirty water bag to me is awesome. The prefilter really helps in my opinion.
The gravity filter system to me is the best thing ever invented... ha!"

I found the sawyer syringe works on the platypus filter just as well

Bulldogge62:I found the sawyer syringe works on the platypus filter just as well"

I had a platypus filter that completely stopped working while stored between trips. The sawyer syringe worked great at getting the filter flowing again. I used a long soak in distilled water and then started back flushing with the syringe. My theory is that the minerals in the tap water can slowly plug up the hollow tubes. So now I always flush with distilled water before I put it away.

I find the Platypus filter is a bit faster than the Sawyer in the beginning, probably due to its .2 micron average filter rating compared to the Sawyers .1 micron absolute filter rating. The Sawyer syringe works great and we are over 50 days for 2-3 people and still going. I have been afraid to use the syringe with the Platypus filter as I am not sure it was made for that kind of pressure, so we back flush with the clean bag. Be sure to REMOVE the dirty bag or you will just run the same green gob of goo back in to the filter again when you reverse it. It is interesting that the Platypus is rated to 400 gallons and only .2 micron, while the Sawyer squeeze is rated to 100,000 gallons and filters to a superior .01 absolute micron level. I know the squeeze and mini were designed to be exceptionally durable for long term solutions in foreign countries and can take the syringe back flushing, just not sure about the Platypus. The company says to only back flush with the bags. Using them this way, the Sawyer eventually overtakes the Platypus in filter speed. One last warning, never ever let the filter dry before back flushing or back flushing will do little good. ALWAYS back flush before storing for more than a day.

So tired of replacing expensive platy filters after a week. Would never go without a backup. Ordered a Sawyer this time. Hoping for better luck. Thanks for this thread. It seems I am not the only one.

Bluebirdpaddler: "So tired of replacing expensive platy filters after a week. Would never go without a backup. Ordered a Sawyer this time. Hoping for better luck. Thanks for this thread. It seems I am not the only one.
"

I've only had to replace a platy filter once, and that was after about 6 years of use, maybe 3-4 weeks each year.

I do backflush after each 4L flitered...and I backflush onto the ground, not into the bag. And I let the water settle in the dirty bag if it seems to have sediment, and tip it slightly away from the outflow so the sediment doesn't flow straight into the filter.

Have toyed with the idea of sawyer filters, they are so much cheaper. I kinda hate the thought of having to bring the syringe along, and then I'd want a spare in case it breaks.....can you just backflush using the same method you use for platy filters?

dogwoodgirl: "

Bluebirdpaddle...and I backflush onto the ground..."

Sounds like a better solution.