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2 gram back flush for sawyer squeeze
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Greg Mihalik
(greg23) - M

Locale: Colorado
Re: enough pressure on 06/29/2013 13:04:49 MDT Print View

Out of the box, and after priming, my PointOne had an initial flow rate of about 1 liter per minute.

I acquired significant degradation from microscopic algae in the BWAC.

After field backflushing with a bladder it had a flow rate of about 1 liter per minute.

When I got home I backflushed with house pressure and ran a bleach solution though it.

I checked again and I had a 1 liter per minute flow rate.

It's an easy thing to check.

And a leaning on a Platy provided enough pressure to get the job done, in this case.

Edited by greg23 on 06/29/2013 19:55:52 MDT.

Stephen Parks
(sdparks) - F

Locale: Southwest
Re: enough pressure on 06/29/2013 13:54:51 MDT Print View

"If you use an adapter and a short piece of hose and a syringe with a tip that fits into the hose, you can get far far higher pressure for backflush, simple physics, force per square cm, plunger has more force, and that's brought down the small opening."

That is incorrect.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: Re: enough pressure on 06/29/2013 14:29:48 MDT Print View


Edited by greg23 on 06/29/2013 14:31:14 MDT.

Harald Hope

Locale: East Bay
That is incorrect. on 06/29/2013 18:01:10 MDT Print View

Enlighten me please. So you're saying that if I hang a bag of air over my bike tire I can get up to 90psi? No more need for an awkward pump with a cylinder and a plunger? Awesome. I'll have to try that next time I get a flat, lol. If you're going to say something is 'wrong', at least make an effort to explain why it's wrong, particularly when it makes little sense to say so. Not saying you're not right, but you have said nothing at all beyond typing a few words, that's not meaningful. As Ricky said in the old Lucy show, "'splain, Lucy".

The other comment above however is more to the point, one can measure these things roughly, assuming you're using actual timers and actually measured quantities so that 3% degradations aren't missed, etc. So if you use a measured start quantity, and a real timer, and keep logs, avoiding 'about the same' type measurements, one certainly could make some good data points.

I'll look out for that in the future, though I won't test on my own filter. It's a good thing to track though.

Edited by hhope on 06/29/2013 18:04:22 MDT.

Tom D.
(DaFireMedic) - M

Locale: Southern California
It should still work on 06/29/2013 21:18:31 MDT Print View

Harold, you very well may be right. Sawyer recommends a strong backflush. But I think the cap method is still a viable way of field backflushing. Most of the reports of the Sawyer filters slowing to a crawl (my inline did this) are when the filter dries out in storage, not usually on a hike. If you need to backflush it to remove particulates that have accumulated during a hike, the cap method should provide enough pressure for this. Once flowing well, the filter generally does so for the duration of the hike unless it has a chance to dry out over several days. Once at home after the hike, the filter can be thoroughly backflushed with high pressure.

I'm just throwing out thoughts based on my experiences with the filters and as usual, I could be wrong. But I do think the cap method would do the job on a hike.

FWIW: The Squeeze filters are $29 right now with a single 32 oz bladder at Walmart. I couldn't find it cheaper online and I picked one up.

Stephen Parks
(sdparks) - F

Locale: Southwest
Re: That is incorrect. on 06/29/2013 22:59:43 MDT Print View

Hi Harold. I hate to read threads that start off with someone being helpful and then degenerate into some other people arguing about some mildly related topic, so I didn't want to contribute to that effect, but I guess I've gone too far already. I took your statement to mean that you claim that adding a piece of hose will increase the pressure to the filter. Now that I've had some much needed sleep - it still reads that way to me. If that is indeed the claim, it is incorrect. The tubing will not increase the pressure. Actually it would only decrease the pressure output as a result of viscous losses.

As for supporting claims - you first :) I don't see any support for your claim that sufficiently high pressure cannot be generated with a bag - only postulations, no?

And for your bag of air, if you take a probabilistic view of the universe, it could indeed spontaneously inflate your bicycle tire, it is just exceedingly unlikely to happen when you want. Or ever. But statistically possible. (I offer no support of this claim, and admit I'm out of my area of expertise here.)

Kevin Gurney
(kwgurney) - M

Locale: SF Bay Area
Re: enough pressure on 06/29/2013 23:44:28 MDT Print View

What a timely topic! I just got a new Sawyer Squeeze and have used it one night in the field. I've been trying to decide if the large syringe needs to go in my repair kit bag in the field, or if I can risk leaving it at home for shorter trips. And then this space saving suggestion comes along. I love these forums...

But let's assume that this water-bag-to-Smartwater-top method actually does produce equal or more pressure than the syringe. I would be concerned that the bag - especially the Sawyer-provided bag - would be more likely to burst when backwashing a particularly clogged filter. I have more faith in the syringe's ability to take ("make", really) the pressure. Any thoughts on or experience with this? The last thing I would want is to have no way to backwash the filter in the field if that's something I think is going to need to be done.

And to settle the bet about which is mightier, the syringe or the Smartwater, is altitude is a proxy for pressure? It's been a long time since high school physics, but if I can squirt a stream of water into the air using two different mechanisms, all things being equal the mechanism that makes the stream go higher is producing more pressure. If true, this should be a very simple - and fun! - experiment to conduct.

Thoughts on this, anyone?

Tom D.
(DaFireMedic) - M

Locale: Southern California
Re: Re: enough pressure on 06/30/2013 09:31:06 MDT Print View

I've had my Sawyer inline for over a year and probably 400 or so miles of hiking with it. Its very unlikely that you would need to backflush it on shorter trips. Even with longer trips, backflushing is not something that you often need to do. We used mine for 3 people on the JMT last year over 18 days and didn't backflush during the hike at all. If for some reason the filter got so clogged that I needed to backflush but couldn't, I always carry a few wrapped purification tablets for emergencys. But I doubt that that will happen.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: Re: Re: enough pressure on 06/30/2013 10:45:03 MDT Print View

I killed a HikerPro over the course of 4 days on the CDT in Colorado. Water sources were marginal, but drinking was not optional.

I killed a Hiker Pro in about 2 weeks in the BWCA. BWCA has a microscopic algae that is notorious for this. On our last trip there I took a PointOne and killed it in about 10 days. Maybe got 75 liters out of it. So I back-flushed and continued using it.

That's why I now take a filter I can back-flush.

I'm glad you've had good luck and sad I've had bad luck.

But I no longer "...doubt that that will happen"

Daryl and Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Re: Re: Re: Re: enough pressure on 06/30/2013 11:07:10 MDT Print View

The flow rate of my Sawyer reduced significantly after 4 days use in the Lost Creek Wilderness of Colorado last week. Our hiking partners had a new Sawyer and did not experience flow reduction.

Water was clear but my wife stirred up a bit of sediment on one or two fillings. I have a piece of mesh in the inlet end of the filter and did not see anything retained by it.

In-the-field backflush capability is desirable to me. I'm with Greg.

Edited by lyrad1 on 06/30/2013 15:38:53 MDT.

Harald Hope

Locale: East Bay
clarification on 06/30/2013 11:26:40 MDT Print View

Stephen Parks, it can hardly be called 'off topic' to note that a method may in fact be incorrect, although alluring. So this is in fact strictly ontopic, exceedingly so, the topic being backflushing a sawyer squeeze.

If I wasn't clear, the reason I use a tube is not to increase pressure, but to make mating the syringe tip to the sawyer work way better, no leaks or misses. Trying to jam the one they provide against the hard plastic does sort of work but it's a pain. Since I already use the clean end adapter with a hose to get the water into the clean bottle, this is zero extra weight. You can also suck the water out of the sawyer before packing it up, the benefits are significant.

I realized after posting this that this question can be fairly trivially tested. With a 2oz syringe, ideally not with the catheter tip that sawyer provides, but with the longer nozzle that lets you insert it into a soft tube firmly, you can squeeze out 2 oz of water in about 1 second, give or take. Hard to time it exactly. This yields of a flow rate of roughly 120 oz per minute, but a flow rate that starts instantly, no buildup. Now we have a standard to judge against. That's 7.5 pints, or roughly 4 quarts a minute. The thing that sawyer specifically warns against is inadequate pressure forming a center channel after which you will never achieve a full clearing out of the sawyer because the water will always then follow the path of least resistance after that point. I believe that to achieve this 1 or 2 second flow rate with a platy type bag will yield a popped bag in not too long, but it's easy to test empirically so there's no need to speculate, how hard to squeeze a bag to get this burst. Remember, you don't want to build up to this rate, you want it instant to avoid forming the center channel issue.

If it takes 2 seconds to empty the syringe, then you have a flow rate of 2 quarts per minute. I'd have to time it to see what it actually takes.

The syringe, because it is a pump, which you can apply focused force on via the plunger, because you squeeze it between your thumb and fingers, using leverage, allows you to achieve this pressure/flow rate in a consistent manner, every time.

So all alternate methods can be easily tested, simply do whatever you're going to do for between 1 and 2 seconds, measure the flow out with a measuring device accurate enough to measure ounces, and there you have it. The flow rate was either in the recommended range or it was not. If you get this 2 oz in about 1, 1.5 seconds (that's counting at normal speaking speed, one one thousand) then you do in fact have an awesome 2 gram backflushing system, if it is far under that, you do not.

However, at $29 for a sawyer squeeze filter, which for those of us using hiker pros remember, is I believe less than a 200 gallon rated, non backflushable replacement filter costs, this is not a really major problem.

My apologies to any violations of physics, which I am trying to correct by noting very simple empirical facts of actual flow rates, which are measurable, and require no speculation.

So give it a try, attach devices, start backflush, into accurate measuring device, note measurement of liquid after 1 second, then 2 seconds. This test takes a few minutes to carry out.

[added]holding the sawyer and and squeezing the syringe with one hand, it took about 1.25 seconds to get the water through, 2 oz. If I put the sawyer on the ground and held the syringe in two hands, I could do it in 1 second easily. So that's actual data point 1 for those interested in such things. lol, what we do for the sake of science....

a long nozzle 2oz / 60ml weighs 36 grams roughly.

As a side note, I'd been considering the use of smaller syringes to get more compact but this discussion has finally convinced me it's a bad idea to try to save weight that way, alluring as it is re size and weight and overall compactness. From now on I will consider the weight of the sawyer to include the syringe.

I'm going to update those postings where I suggested using smaller syringes and remove that advice, I simply had not considered flow rates over time adequately, so this thread was quite useful, as were the comments of an engineer on that blog posting who also pointed to flow rates (the tubules apparently hold roughly 1/2 oz of water in volume).

When I tested using a bag for backflush, these were my results:

I did, by the way, try using two screw on ends with hoses, to try to use a bladder bag to backflush, but I couldn’t generate enough pressure, and it felt like I’d probably end up bursting the bag over time if I tried it, and it really didn’t get much more than a dribble when backflushing.

Edited by hhope on 06/30/2013 12:31:41 MDT.

Drew Jay

Locale: Central Coast
Actual flow rates on 06/30/2013 17:50:57 MDT Print View

I just tested this using the new style Squeeze with SmartWater nozzle fit over the Sawyer nipple. I could easily backflush 60cc of water through the filter in 3.5 seconds. There was no delay, and it did not take inordinate pressure on the bag. The syringe took 2.8-2.9 seconds to push the same 60 cc's of water. Yes the syringe flows more, but not much more.

In summary, the SmartWater setup is in my opinion quite adequate for field use and I am not the least bit worried about overstressing the bag. After all you are likely to backflush maybe once a trip.

Edited by drewjh on 06/30/2013 17:52:20 MDT.

Tom D.
(DaFireMedic) - M

Locale: Southern California
I doubt that will happen on 07/01/2013 04:22:52 MDT Print View

Greg & Daryl,
Its good that you recognize the need to be able to backflush on a trip. When I said "I doubt that that will happen", I was referring to a situation where I would have to turn to my back up chemical treatment because I was unable to backflush the filter. Im confident that I will be able to accomplish it even without the syringe by using the method described in this thread. I never implied that I would not encounter a situation where backflushing would be necessary. I already have.

Stephen Parks
(sdparks) - F

Locale: Southwest
Re: clarification on 07/01/2013 07:59:00 MDT Print View

You have me picturing a syringe as pogo-stick for maximum output. Maybe a trekking pole attachment is needed for the long upright section.

Kathleen B

Locale: Pacific Northwest
2 gram back flush for sawyer squeeze on 07/08/2013 14:37:03 MDT Print View

Eric - thanks a bunch for this great idea. Today I was finally in a store that sells SmartWater bottles with the fliptop lid. I attached the lid to my Evernew, and the blue part fits nicely into the Sawyer Squeeze and squirts through just fine. I must have a different model than you, because I didn't need the second lid to attach to the Sawyer itself. Instead of carrying a bulky, 1.17 oz syringe, I can now carry the tiny .12 oz cap. Thanks again!

Paul Andronico
(Jakesandwich) - MLife

Locale: S.F. Bay Area
Thanks! on 07/13/2013 19:04:44 MDT Print View

Thanks Eric and Drew. I replaced the original, .20 ounce drink cap/cover from the Sawyer Squeeze with the .18 ounce Smart Water bottle drink cap/cover. So the replacement is actually lighter than the original, and I can leave the bulky syringe at home. Fantastic!