Diatoms clogging Sawer water filter

[Dave @ Oware]

Just spent awhile in the Hoover and Yosemite wilderness. Despite being very clear, the lakes rapidly clogged all our squeeze filters requiring constant back flow cleaning and with mediocre results. One of our party was a professional in high lake water quality and monitors Sierra Nevada lakes. She said it was likely diatoms clogging the pores. Apparently they can be invisible and tenacious.  She carried an expensive pump filter. It worked great until it didn’t.

Anyone have solutions (liquid or otherwise) to cleaning filters from these little creatures?

[Terran Terran]

Did you try it without pressure?

[Jerry Adams]

attach the filter to a faucet and backflush a lot of water?  With more pressure, the hollow tubes expand more which makes the pores bigger so any small particles would dislodge.

you could try the treatment for a mineral clogged filter, like flushing it with vinegar or CLR, although it doesn’t seem like that would address this problem

[Jon Fong / Flat Cat Gear]

The Sawyer fiter size is 0.1 microns

From Wikipedia

Diatoms are used to monitor past and present environmental conditions, and are commonly used in studies of water quality. Diatomaceous earth (diatomite) is a collection of diatom shells found in the Earth’s crust. They are soft, silica-containing sedimentary rocks which are easily crumbled into a fine powder and typically have a particle size of 10 to 200 μm

If the smallest diatom size is 10 micron then it is 2 orders of magnistude larger than the filter size.  This makes it unlikely that they would clog a filter.  My 2 cents.

[Ray J]

Jon,   But anything may clog the filter. Silt, mud. The way I’m thinking is that the diatom would “clog” it by simply being in the filter.  But given the size you report, wouldn’t stick in the tubes.  Given the size I would think they would back flush out easily.  Or am I missing my coffee?

[Dave @ Oware]

Lots of good stuff to consider. I will ask more questions of my friend. It is the live diatoms (algae) as I understand, and they are sticky. It may be that parts of the animal get caught in the openings. In googling I found that aquarium filters use diatomaceous earth to filter diatoms!  I am going to try lots of flushing at home and also a dilute vinegar. The vinegar is a disinfectant anyway. It was something in the clear mountain lakes as all 5 of the filters had trouble. Global warming and aeolian transport changing our water up high?

[Jon Fong / Flat Cat Gear]

The interesting thing about filters is that they tend to get more efficient over time.  Efficient in that their ability to filter our material improves (though the flowrate decreases).  Given the examples of the diatoms, these are huge compared to the filter size.  The junk will form a large labyrinth that small particles can flow around.  Think of it this way, picture the filter as having a 1” diameter and you are filtering out water than contains bowling balls and let’s assume that the bowling ball is 10 inches in diameter (or 1 order of magnitude).  As the bowling balls pile up, there is still plenty of space for the water to flow around.  Now picture a stack of bowling balls 50 feet deep.  The particles can still pass though but the flow rate will be reduced.

Absolute particle size ratings are based upon hard objects that get through the filter media.  There is no way to evaluate particles that have a gel or are compliant.  This is one of the reasons to take something like the MSR Sweetwater system.  It is a ceramic filter that you abrade away the outer coating that is clogged to reveal a fresh new layer of filter.  That and it is field serviceable.  My 2 cents.

[Terran Terran]

https://shop.prmfiltration.com/collections/bag-filters/products/1-size-5-micron-liquid-filter-bags-polyester-felt-polypropylene-ring

It may fit inside a CNOC. I don’t see it recommended anywhere, but a drop of soap will dislodge about anything, though you’ll have to flush out the soapy taste. I don’t see where it harms anything.

[Brad W]

What was your backflush method? Were there no inlet streams to the lakes easily accessible?

[DirtNap]

My Sawyers tended to get wierd after a season or so. My Hydroblues, I can’t kill them. Clean them with a chlorine solution after every trip. Flush with a mild vinegar mix until clear and go. Nice thing is you can screw them on to the lip of your smart water bottle and get really good back flush pressure. I didn’t need to back flush once on my Grand Canyon 10 day packrafting loop in June. But we did drink a fair amount of wild water, mostly from springs.. YMMV of course.

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