Pump Filter Using Sawyer Mini

[Sam Farrington]

The filter, ready to pump. Water is sucked through the filter and out the pump:

And with the handle closed:

A pump filter can save a lot of fooling around with filling and compressing water bags, and can lift water from shallow springs, or from the surface of pools without disturbing algae, silt and other stuff that can gum up the works.

This one is powered by a Heinz Easy Pump, suggested here by David Thomas, and available at Ebay, Amazon, and even some Walmart stores for under ten dollars. The spring inside has been removed. Also tried was a similar Pennzoil pump, but its piston broke quickly, The vent on the pump was closed by wrapping Scotch "Stretchy" tape a couple times around the pump cylinder just below the screw-on cover.

After looking at other light filters, like the pricier Platy Gravityworks and the slightly heavier RapidPure Scout 1.2L, I benefited greatly from some advice about the Mini that was kindly offered by Daryl and Daryl. My conclusion was that the Sawyer Mini will work reliably with a prefilter and clear water, coupled with backflushing before and after backpack trips and every few days while hiking.

So the pump filter is designed to be easily backflushed by its own pump when set up like this:

A press fit vinyl coupling was added to the intake of the pump so the filter can be easily disconnected and re-attached to the outflow tube. This also makes it easy to separate the pump and the filter for storage in the bag shown below.

The prefilter is from a Sweet Water Walk-About. The prefilters were sold separately, and may still be found under the MSR brand (MSR Sweetwater Prefilter from Amazon).

Packed in a bag made from silnylon from Thru-Hiker, with the prefilter and tube in a separate zipped compartment, and with the extra inlet tube for backflushing and a float, the whole works weighs 6.8 ounces:

For easier packing, the outflow tube will be changed to much more flexible silicone tubing when the right size is found.

The prototype was used on a backpack during summer 2014, and performed reliably. It takes around 30-35 almost effortless pumps to fill a quart bottle, which is much better than was experienced with another filter weighing close to a pound and much harder to pump. The pump has also been self-priming.

Unfortunately, the Mini on the prototype was not backflushed before storage after use. It took a lot of hard pumping later to get it working again, and it is still hard to backflush, so a replacement was obtained. Daryl and Daryl suggest hot water, vinegar and even faucet pressure to backflush if there is serious clogging. It seems that these filters accumulate particulate gradually, and if there is not regular backflushing, the gunk will dry out and congeal in layers that build up and will eventually clog the filter, defying backflushing. It has also been suggested that the Minis not be allowed to dry out during storage.

Edited to add method to close pump vent, and correct source of prefilter

[Daryl and Daryl]

Samuel,

Thanks for the post. Lot of good thinking and work represented here.

[Erik G]

Very nice work. Pump filters like this can be highly beneficial as mentioned above.

I must say, this looks and works a lot like the MSR Hyperflow. Similar hollow fiber filter technology, similar pumping mechanism, easy field backflushing, can be used as a gravity filter. Total weight of the Hyperflow is 7.8oz with tube, pre-filter and storage bag.

With this setup though, "replacement filters" are substantially less expensive: $25 for a Sawyer Mini vs. $40 for a MSR replacement cartridge for the Hyperflow. Cost of the pump and tubing is certainly much lower too. And slightly lower weight, and MYOG. All that adds up to a win in my book.

Well done!

[rick .]

Great build. I hope to have this pumping by spring.

The weight of the pump elements are offset by omitting a dirty water bag (and backflusher if you carry it)

If you have the information, I'd love links to the materials, especially the fitting at the pump-to-filter joint.
Camelbak style bladder users can get a fitting to pump directly back into their bladder without removing it from their pack.

Edit. You are supposed to backflush with cleaned water, how do you avoid contamination from the (dirty) yellow tube?

[Christopher *]

Ooooooh. I've been waiting for this post since you first started experimenting with pumps. I live in the east, and know the frustration of the shallow seep!!! An inline pump is such a great idea!

"the whole works weighs 6.8 ounces"

So does this weight include the mini?
Thanks for the post. I may need to follow your lead.

EDIT: I can't quite recall but wasn't it your idea to utilize heat shrink tubing as the output for a gravity filter? (Someone here did that. In my mind I give you the credit.) Considering the flow is always positive (won't collapse the tube), would that work for your "output" here, or is there too much applied pressure?

[Joe S]

Great job. May try my own build out.

[Sam Farrington]

Erik,

A reason for the MYOG was disappointment with the Hyperflow. I bought and returned Hyperflows when they first came out, and a year or two later hoping the kinks might have been taken out. Both times, the filter would not pump any water, right out of the box and using drinking water from the tap. The instructions for backflushing were a poor translation into English, and IMO, incoherent. Rather than fool around and try to get the filters to work, they went right back into the box to be in a condition to obtain a full refund on return. I understand that some have had good luck with the MSR, and others not, and this is reflected in the BPL member reviews.
Whatever the problems with the Mini may be, haven't heard yet of one not working right out of the box.

The Mini has been $20 at Walmart for some time, but I see you are in sunny CAL. Are there Walmarts out there? We are getting another winter back here that looks to have three Janaurys like last year. Sunny CAL sounds like a great place to be right now.
(Oops, just recalled that unlike NH, you may have a sales tax.)

[Sam Farrington]

rick,
Re: 'I'd love links to the materials, especially the fitting at the pump-to-filter joint.'

Dumb MYOG story, but the prototype was attached to the filter by tubing, which was bent double when the filter was folded against the side of the pump for packing in the bag. The tubing kinked of course, and eventually it would have cracked or become severely narrowed. So went looking for accordion type tubing, and found some on a little foot pump under $5 in one of those stores that carries cheap imported tools, like 'Cal-Hawk.' The tubing was no good, but included was a small fitting that was perfect to screw into the Easy Pump with a little shaving and use of a tap and die and some high grade Epoxy. McMaster-Carr has some really good 1/4" non-kink accordion tube, but it is $40 a foot, and had decided that a coupling would work better anyway with the need for regular re-attachment for backflushing. So I guess the short answer is hunting around hardware stores and plumbing supply for something that fits, or doing a little drilling as a last resort.

The other material not mentioned in the OP is the outlet tube, which came out of the Mini box I think; but as mentioned, it will be replaced with silicone tube. If not found locally, McM-Carr should have it in the right size at a reasonable price.

There was also the question of how to hold the end of the output tube inside the lip of the bottle. In the photos is a pic of the adapter used for Nalgene bottles, but have already decided to use Planter's quart bottles, one of which is also sitting at the edge of one photo, because they are lighter and handle better. They don't fit the Nalgene adaptor, but unclear in the photos is the little spring like attachment on the end of the output tube that clamps over the lip of whatever bottle or pot you want to fill. These spring clips used to be common on BP filters, but are now rare. If anyone knows where to get them, please post.

Lastly, re your query about water for backflushing. I asked that myself on a thread, and Jerry responded advising to pump some clean water using the filter. That assumes the filter isn't totally clogged, as is the case if backflushing is done regularly before the filter starts to clog. Also, there are some water sources coming out of springs that can probably be trusted. Then there is boiling or tablets, which are also the last resort if the filter fails. So the yellow silicone tube should remain uncontaminated.

[Frank T]

Great job Samuel.

Amazon has quite a variety of silicone tubing. Here is a link to some 1/4" I.D. thinwall tubing I use in my gravity filter.

http://www.amazon.com/gp/product/B000FP0IES/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1

It's fairly spendy at $24 for 10 ft. but thicker tubing is cheaper and not that much heavier.

[Sam Farrington]

Christopher*,

Yes, the weight includes the Mini. Everything needed is in the bag on the scale.
The Nalgene bottle adaptor was left out because I'm going to the lighter Planters bottles.

No, the heat shrink was someone else's idea, but don't recall who. I just need to find some of the highly flexible silicone tube that is the same inner diameter as the current output tube. Only because the silicone tube will fold easily for packing, and will resume its normal shape without adopting a permanent kink. With the right size tube, I had no problem getting a tight and strong fit on the pump output, which was cut shorter so the pump would pack more easily.

Thanks to all for your comments. Anyone is welcome to PM me, but since I can't reply due to an undiagnosed computer glitch, please include an email address for a response.

Should also mention that if the Mini does not work out, that's not the end of the story. The Platy weighs under 2 oz also, and probably could be applied to the same use. (The weights given are usually for a dry unit that increases in weight in use.) But it would cost 3 times the price of the Mini to find out for sure.

[rick .]

Thanks for the reply 21 days ago! (I forgot to watch this thread, and searched to pull it back up)

I think this is worth giving a shot, with less than $20 for the key materials, you have both the lightest and cheapest pump filter available. Man I hate squeezing bags of water.

I also came across a youtube video (now lost) that showed the sports cap from a Smartwater can be used to flush the mini. Just screw it on to a clean water bottle/bag, hold it against the outflow and squeeze clean water back through the filter.

[rick .]

I dry assembled this last night and was pumping water!

I just used the ketchup can pump directly on the clean end (the little plastic tip on the pump slides over the clean end of the sawyer, a bit loose but works). An old camelbak hose and the sweetwater pre-filter completes the basic setup.

If you screw a bladder/bottle on the back of the sawyer, you don't need the hose. However, the hose is helpful for sucking up from a hard to reach source (like a sump or a puddle).

I need to take the whole rig to a hardware store and see what I can refine, but it works fine out of the box (at the kitchen sink, trail use will be the real test).

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